"Pharmaceutical Sciences, Faculty of"@en . "DSpace"@en . "UBCV"@en . "Woo, Wendy Weng Wah"@en . "2011-06-23T22:42:08Z"@en . "1968"@en . "Master of Science - MSc"@en . "University of British Columbia"@en . "A completely automatic continuous flow dissolution procedure was developed and tested. Pertinent dissolution conditions were investigated and chosen to study the dissolution characteristics of seven brands of phenylbutazone tablets. A pumping system enabled the simulated digestive fluid to flow from the dissolution vessel into the flow cell of a recording spectrophotometer for a continuous recording of the drug concentration in the dissolution medium, which was gradually changed from an acidic medium to a basic one.\r\nFrom the \"in vitrott\u00E2\u0080\u009D data obtained by this test procedure, a T\u00E2\u0082\u0085\u00E2\u0082\u0080% value of 120 minutes was chosen as a limit of acceptance for the test products. The \"in vivo\" characteristics of six of the brands were compared with those observed for a pharmaceutically acceptable product. Of the seven test products, only four were acceptable on the basis of both the \"in vitro\" and the \"in vivo\" data. Correlation of the \"in vitro\" and the \"in vivo\" data resulted in \"least squares\" lines with negative slopes."@en . "https://circle.library.ubc.ca/rest/handle/2429/35725?expand=metadata"@en . "THE BIOPHARMACEUTICAL PROPERTIES OF SOLID DOSAGE FORMS The Operating C h a r a c t e r i s t i c s of a Continuous Flow D i s s o l u t i o n Apparatus by WENDY WENG WAH WOO B. S. P., U n i v e r s i t y of B r i t i s h Columbia, 1 9 6 6 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF Master of Science i n Pharmacy (M. S. P.) i n the Facult}' of Pharmacy We accept t h i s t h e s i s as conforming to the req u i r e d standard. THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1 9 6 S In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h C olumbia, I agree t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and Study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by the Head o f my Department or by h.i.'S r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f *7U OLA^iOi-H^ The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Date f 7 - H - L? fr. i i ABSTRACT A completely automatic continuous f l o w d i s s o l u t i o n procedure was developed and t e s t e d . P e r t i n e n t d i s s o l u t i o n c o n d i t i o n s were i n v e s t i g a t e d and chosen to study the d i s s o l u t i o n c h a r a c t e r i s t i c s of seven brands of phenylbutazone t a b l e t s . A pumping system enabled the simulated d i g e s t i v e f l u i d to flow from,the d i s s o l u t i o n v e s s e l i n t o the fl o w c e l l of a r e c o r d i n g spectrophotometer f o r a continuous r e c o r d i n g of the drug c o n c e n t r a t i o n i n the d i s s o l u t i o n medium, which was g r a d u a l l y changed from an a c i d i c medium t o a ba s i c one. From the \" i n v i t r o t t data obtained by t h i s t e s t procedure, a T^Q^ value of 120 minutes was chosen as a l i m i t of acceptance f o r the t e s t products. The \" i n v i v o \" c h a r a c t e r i s t i c s of s i x of the brands were compared w i t h those observed f o r a pharmaceutically acceptable product. Of the seven t e s t products, only f o u r were acceptable on the b a s i s of both the \" i n v i t r o \" and the \" i n v i v o \" data. C o r r e l a t i o n of the \" i n v i t r o \" and the \" i n v i v o \" data r e s u l t e d i n \" l e a s t squares\" l i n e s w i t h negative slopes. M. Pernarowski, Ph. D. Supervisor i i i TABLE OF CONTENTS Page I . INTRODUCTION 1 I I . LITERATURE SURVEY 5 I I I . THE \"IN VITRO\" CHARACTERISTICS OF PHENYLBUTAZONE (a) The S o l u b i l i t y of Phenylbutazone i n Buff e r e d S o l u t i o n s 28 (b) Determination of the I s o s b e s t i c P o i n t 2 9 (c) Determination of A b s o r p t i v i t y Value 3 0 IV. THE OPERATING CHARACTERISTICS OF A CONTINUOUS FLOW DISSOLUTION APPARATUS (a) D e s c r i p t i o n of the Apparatus 35 (b) C a l i b r a t i o n of the Recorder 3 6 (c) The E f f e c t of S t i r r i n g Rate on D i s s o l u t i o n 3 9 (d) The E f f e c t of Pumping Rate on D i s s o l u t i o n 42 (e) Test Procedure 45 (f) R e s u l t s 4 6 V. THE \"IN VIVO\" CHARACTERISTICS OF PHENYLBUTAZONE TABLETS 5 6 V I . \"IN VIVO\" - \"IN VITRO\" CORRELATION 6 1 i v Page V I I . DISCUSSION 67 V I I I . SUMMARY 70 IX. BIBLIOGRAPHY 71 LIST OF TABLES Page I . The E f f e c t of S t i r r i n g Rate on D i s s o l u t i o n 41 I I . The E f f e c t of Pumping Rate on D i s s o l u t i o n 43 I I I . D i s s o l u t i o n Data f o r Seven Brands of Phenylbutazone Tablets 50 ^50% anc* ^9he twenty-three products d i s i n t e g -r a t e d and r e l e a s e d t h e i r phenylbutazone content to the medium q u i c k l y . A standard T^Q^ value of 120 minutes was chosen by these workers on the b a s i s of the data a v a i l a b l e . I t was not p o s s i b l e to c o r r e l a t e the \" i n v i v o \" data to t h a t obtained \" i n v i t r o \" . For the t a b l e t s examined, the best c o r r e l a t i o n was s t i l l to t a b l e t d i s i n t e g r a t i o n time. However, maximum d i s i n t e g r a t i o n times would be more meaningful than mean d i s i n t e g r a t i o n times. Nash and Marcus (20) used a p e r i o d i c solvent exchange method to study d-amphetamine s u l f a t e \" s u s t ained r e l e a s e \" capsules and tripelennamine h y d r o c h l o r i d e \"sustained r e l e a s e \" t a b l e t s . The t e s t sample was put i n t o a 600-ml. Buchner type funnel w i t h a medium p o r o s i t y f r i t t e d d i s k f i l t e r bed and g e n t l y a g i t a t e d i n 400 ml. of simulated g a s t r i c j u i c e . F i n e r p o r o s i t y f i l t e r s prevent proper drainage of the f l u i d while coarser types leak during sampling p e r i o d s . P o s i t i v e a i r pressure was maintained between sampling periods to prevent leakage. A f t e r t h i r t y minutes, 200 ml. was drawn o f f by vacuum through the f i l t e r bed i n t o the s u c t i o n f l a s k and c o l l e c t e d i n a 250 ml. beaker. A . f o u r - i n c h standard two-way stop cork fused i n t o the bottom of the s u c t i o n f l a s k f a c i l i t a t e d the removal of f l u i d samples during the course of each run without u p s e t t i n g the p o s i t i v e pressure at the bottom of the f i l t e r bed. An a d d i t i o n a l 200 ml. p o r t i o n of simulated g a s t r i c f l u i d was added to the funnel to replace 21 the withdrawn volume. Further samples were withdrawn at one and a h a l f , two, th r e e , f i v e , seven and twenty-four hour i n t e r v a l s , each time w i t h replacement of the f l u i d . Norby (22) developed a continuous solvent exchange system to study the re l e a s e p a t t e r n of \"su s t a i n e d r e l e a s e \" t a b l e t s . One u n i t of the drug was placed i n a beaker c o n t a i n -i n g ten ml. of d i s s o l u t i o n medium at t h e r m o s t a t i c a l l y c o n t r o l l e d temperature. This s o l u t i o n was kept at a constant l e v e l w i t h the r e s e r v o i r of f r e s h medium to ensure a constant volume i n the d i s s o l u t i o n v e s s e l . The medium from the d i s s o l u -t i o n v e s s e l flowed through tubing which had a cott o n f i l t e r at the open end i n t o a c o l l e c t i n g v e s s e l at a r a t e ( 0 - 1 0 ml./min.) c o n t r o l l e d by a magnetic v a l v e . There' was an automatic mechanism c o n t r o l l i n g t h i s v a lve which c o n t r o l l e d the f l o w r a t e through the system to give a reprod-u c i b l e t e s t . The opening and c l o s i n g of the valve was c o n t r o l l e d by an e l e c t r o n i c a l l y d r i v e n mechanical, device. The s t i r r e r was power d r i v e n . A screen around the p r o p e l l e r p r o t e c t e d the t e s t ' p r e p a r a t i o n from coming i n contact w i t h the blades. The s t i r r e r was moving f a s t enough so that the drug was moving f r e e l y and d i d not s t i c k to the sides or the bottom of the d i s s o l u t i o n v e s s e l . Concentration of the medium was determined e i t h e r by a n a l y s i n g a f r a c t i o n of the c o l l e c t e d medium or by a continuous r e c o r d i n g on a spectro-photometer. 22 I n t h e i r study of the e f f e c t of compression pressure on d i s s o l u t i o n , Ganderton and h i s co-workers (7) used two \u00C2\u00B0 methods to t e s t compressed t a b l e t s of phenindione of d i f f e r -ent f o r m u l a t i o n s , a l l c o n t a i n i n g 100 mg. c r y s t a l l i n e l a c t o s e w i t h 15 mg. of. potato s t a r c h dispersed w i t h i n the granules, over a pressure range of 60 - 2500 Kg.cm. on a s i n g l e punch machine. I n the f i r s t method, the d i s s o l u t i o n v e s s e l was a 2 - l i t r e beaker ( c o n t a i n i n g 1.5 l i t r e s of d i s s o l u t i o n medium) immersed i n a water bath. The medium was s t i r r e d by a perspex paddle 11 cm. i n diameter, held 0.5 cm. above the bottom of the v e s s e l and r o t a t i n g at 56 r.p.m. The two blades of the paddle were 2.5 cm. deep and p i t c h e d at 45\u00C2\u00B0 to promote a x i a l mixing. Two d i a m e t r i c a l l y opposed b a f f l e s 1.3 cm. wide were f i x e d i n the v e s s e l . The t e s t t a b l e t was placed i n a cube of lOOsmesh s t a i n l e s s s t e e l gauze of sides 1.5 cm., r i g i d l y suspended i n the bath 4 cm. from the paddle a x i s and 2 cm. below the surface of the l i q u i d . The t e s t was performed i n 0.001 N.NaOH at 37\u00C2\u00B0C F i v e ml. samples were withdrawn through a f i l t e r tube at s u i t a b l e i n t e r v a l s -over a p e r i o d of one hour, d i l u t e d and assayed. The second method was a continuous d i s s o l u t i o n process, using a c y l i n -d r i c a l perspex c e l l 5.1 cm. i n diameter. A 100-mesh, concave, s t a i n l e s s s t e e l gauze was f i x e d across the c e l l and the t a b l e t h e l d l i g h t l y at the centre w i t h a v e r t i c a l p i n . Water bu f f e r e d at pH 7 was admitted through the centre of the c e l l 23 base and d i r e c t e d r a d i a l l y on the gauze below the t a b l e t . When the t a b l e t was wetted, the r e t a i n i n g p i n was removed and the l i q u i d i s s u i n g from the top of the c e l l was c o l l e c t e d o and assayed. The t e s t was c a r r i e d out at pH 7 and 20 G to a l l o w the d i r e c t assay of the emerging s o l u t i o n without f u r t h e r d i l u t i o n . The f i r s t l i t r e of s o l u t i o n was c o l l e c t e d and assayed. The t e s t l a s t e d approximately eleven minutes, g i v i n g a mean l i q u i d v e l o c i t y i n the c e l l of 0.075 cm./sec. D i s i n t e g r a t i o n t e s t s were c a r r i e d out usi n g the method described i n the B r i t i s h Pharmacopeia 1963. From the r e s u l t s , i t was found that the speed of d i s i n t e g r a t i o n p r o g r e s s i v e l y decreased as the compression pressure increased. The d i s s o l u t i o n r a t e s f e l l s t e e p l y at the low compression pressures and then r i s e to form a peak at pressures which v a r i e d w i t h f o r m u l a t i o n from 500 to 800 Kg. cm. . The rat e then decreased to give an extended high pressure r e g i o n i n which d i s s o l u t i o n r a t e was independ-ent of both pressure and fo r m u l a t i o n . Although very weak and e a s i l y penetrated by the d i s s o l u t i o n medium, t a b l e t s produced at very low pressures d i d not break up e x t e n s i v e l y during the t e s t . L i t t l e fragmentation had occurred so that p a r t i c l e l o s s and d i s s o l u t i o n r a t e were low. At higher pressures, p e n e t r a t i o n s t i l l occurred q u i c k l y and s t r e s s r e l e a s e and the l o s s of small a i r bubbles caused much more d i s r u p t i o n . The van der Waals forces h o l d i n g the t a b l e t together i n the dry s t a t e were i n e f f e c t u a l i n the presence of a l i q u i d of high d i e l e c t r i c constant and p e n e t r a t i o n by the d i s s o l u t i o n medium caused the t a b l e t t o break up. With f u r t h e r increase i n pressure, rebonding of the m a t e r i a l occurred and a stronger and denser t a b l e t was formed, which was l e s s e a s i l y penetrated. P a r t i c l e l o s s and d i s s o l u t i o n r a t e were, t h e r e f o r e , depressed. U l t i m a t e l y , high s t r e n g t h and low p e n e t r a t i o n prevented break-up of the t a b l e t , and d i s s o l u t i o n occurred only from the surface of the t a b l e t and was t h e r f o r e independent of any fo r m u l a t i o n v a r i a b l e s . At low pressure, the d i s s o l u t i o n r a t e of t a b l e t s increased as the f i l l e r s i z e or the granule s i z e decreased. These r e s u l t s i n d i c a t e d t h a t these f a c t o r s g r e a t l y a f f e c t the s i z e of the p a r t i c l e s l i b e r a t e d by p e n e t r a t i o n and break-up. I n the case of the f i l l e r , decrease i n s i z e increased the homogeneity of the o r i g i n a l mix, opposing the formation of la r g e agglomerates of phenindione. Decrease i n granule s i z e modified the d i s p o s i t i o n of the e x t e r n a l s t a r c h , a f a c t o r which has been shown to g r e a t l y a f f e c t p e n e t r a t i o n and break-up of the t a b l e t . Smaller granules would a l l o w i t s more e f f e c t i v e d i s t r i b u t i o n as a h y d r o p h i l i c or antibonding l a y e r . Both these e f f e c t s w i l l disappear at high pressures of compaction when break-up i s depressed and s o l u t i o n occurs only from the surface of the t a b l e t . 2 A continuous f l o w system was designed by Woo ( 33 ) to study eleven brands of commericially a v a i l a b l e t o l b u t -amide t a b l e t s . The d i s s o l u t i o n v e s s e l was a t w o - l i t r e a s p i r a t o r b o t t l e . The rubber stopper at the bottom o u t l e t of the b o t t l e c a r r i e d a short piece of gl a s s t u bing that was connected on the i n s i d e of the d i s s o l u t i o n v e s s e l to a piece of rubber tu b i n g . A piece of very f i n e gauze that covered the open end of the rubber tubing acted as the f i l t e r f o r the outflowing medium. The g l a s s tube that proje ed out of the v e s s e l was connected to a T-glass tube, one arm of which was j o i n e d to an a i r supply, while the other arm l e d to a 500-ml. s u c t i o n f l a s k v i a rubber tu b i n g . The rubber stopper at the top of the d i s s o l u t i o n v e s s e l c a r r i e d a thermometer and an i n l e t tube from a r e s e r v o i r of si m u l -ated g a s t r i c f l u i d . The d i s s o l u t i o n v e s s e l was set on a pyro-magnetstir, that kept the medium i n the v e s s e l at a temperature of 37\u00C2\u00B0G + 0.5\u00C2\u00B0C, and caused the magnetic s t i r r e r i n the d i s s o l u t i o n v e s s e l to s t i r the medium at va r y i n g speeds. The d i s s o l u t i o n v e s s e l was f i l l e d w i t h one and a h a l f l i t r e s of simulated g a s t r i c f l u i d . A f t e r the o medium had e q u i l i b r a t e d to 37 C, a t e s t t a b l e t o f . t o l b u t -amide ( 500 mg.) was dropped i n t o the d i s s o l u t i o n v e s s e l . The s t i r r e r was turned on to give a vigorous s t i r r i n g i n t e n s i t y . A f t e r an i n i t i a l ten minutes, the clamp on the 2 6 tube to the s u c t i o n f l a s k was p a r t i a l l y unscrewed to a l l o w a f l o w r a t e of 500 ml./30 minutes, when s u c t i o n was a p p l i e d . At the same time, the i n f l o w r a t e from the r e s e r v o i r was adjusted to d e l i v e r 500 ml./30 minutes, by p a r t i a l l y unscrew-i n g the clamp on the d e l i v e r y tube. This ensured that the volume, i n the d i s s o l u t i o n v e s s e l was kept constant. During the changing of the s u c t i o n f l a s k s ( a f t e r each t h i r t y - m i n u t e i n t e r v a l ) both the i n f l o w and outflow tubes were clamped o f f by a second clamp. As the f l u i d flowed through the f i n e gauze f i l t e r , p a r t i c l e s of the t e s t t a b l e t c o l l e c t e d on the f i l t e r and caused i t to be clogged up, thus slowing the outflow r a t e . This was overcome by t u r n i n g on the a i r supply o c c a s s i o n a l l y to blow the p a r t i c l e s o f f the gauze back i n t o the d i s s o l u t i o n medium. The d i s s o l u t i o n t e s t was c a r r i e d on f o r a p e r i o d of three hours, c o l l e c t i n g i n t o t a l a volume of three l i t r e s . I n d i v i d u a l analyses were c a r r i e d out on each p o r t i o n of d i s s o l u t i o n medium c o l l e c t e d . D i s i n t e g r a t i o n t e s t s were c a r r i e d out on these tolbutamide t a b l e t s using the o f f i c i a l U.S.P. d i s i n t e g r a t i o n apparatus (30). The d i s i n t e g r a t i o n s t u d i e s were c a r r i e d out without the use of the p l a s t i c d i s k s . The v a r i o u s brands of tolbutamide t a b l e t s seemed to f o l l o w a s i m i l a r p a t t e r n of d i s s o l u t i o n . In the i n i t i a l ten minutes, most of the t a b l e t s broke up i n t o very f i n e p a r t i c l e s or f l a k e s . The rel e a s e of the a c t i v e i n g r e d i e n t i n c r e a s e d g r a d u a l l y t i l l a maximum was reached i n the f i r s t h a l f hour. The l e v e l remained constant f o r about an hour and then g r a d u a l l y decreased due to a d i l u t i o n process by the incoming s o l v e n t , thus g i v i n g a p l a t e a u - l i k e curve. Even though the d i s s o l u t i o n p a t t e r n was s i m i l a r f o r the d i f f e r e n t brands, the total.amount of the a c t i v e i n g r e d i e n t , r e l e a s e d i n three l i t r e s of s o l u t i o n ranged from 60 mg. to 270 mg. No c o r r e l a t i o n w i t h the d i s i n t e g r a t i o n times could be found, confirming an e a r l i e r report by Brudney and h i s co-workers (1). However, the d i s s o l u t i o n t e s t was c a r r i e d out on only one t a b l e t of each product, so d e f i n i t e conclusions about the t a b l e t q u a l i t y could not be made. The d i s s o l u t i o n t e s t described was very time consuming and r e q u i r e d constant s u p e r v i s i o n . Moreover, the f i l t e r i n g system was not too e f f i c i e n t and tend to blog up towards the end of the d i s s o l u t i o n run and hence would be inadequate f o r longer d i s s o l u t i o n runs. 28 I I I . THE \"IN VITRO\" CHARACTERISTICS OF PHENYLBUTAZONE The drug being i n v e s t i g a t e d i s phenylbutazone and i s used f o r the r e l i e f of j o i n t pain caused by rheumatoid a r t h r i t i s , gout, b u r s i t i s and other r e l a t e d d i s o r d e r s . Phenylbutazone ( 1 , 2 - D i p h e n y l - 4 - b u t y l - 3 , 4 P y r a z o l i d i n e d i o n e ) , a weak organic a c i d of pKa 4 . 4 , i s very s l i g h t l y s o l u b l e i n water ( l e s s than 0 . 7 mg./ml. at 25\u00C2\u00B0C) but f r e e l y s o l u b l e i n a l c o h o l (50 mg./ml.), acetone, ether and e t h y l a c e t a t e . Phenylbutazone powder tends to agglomerate and f l o a t on the surface of an aqueous medium. Attempts at r e c r y s t a l l i z a t i o n y i e l d e d long needles that f l o a t on the surface of aqueous s o l u t i o n s . Hence, B u t a z o l i d i n (Geigy) t a b l e t s (which have been reported to give good c l i n i c a l response ( 2 , 27)) were chosen as a standard f o r t h i s i n v e s t i g a t i o n . (a) The S o l u b i l i t y of Phenylbutazone i n B u f f e r e d S o l u t i o n s I t i s necessary, during the d i s s o l u t i o n t e s t , to change from an a c i d i c medium of pH 1.2 t o a pH 6 . 2 . Since the s o l u b i l i t y of phenylbutazone i s a f f e c t e d by the p.H of the d i s s o l v i n g medium, s o l u b i l i t y s t u d i e s were c a r r i e d out i n b u f f e r s of d i f f e r e n t pH valu e s . Procedure - Using the Smith, K l i n e & French d i s i n t e g r a t i o n apparatus ( 2 9 ) , phenylbutazone powder i s put i n t o each of s i x ' b o t t l e s c o n t a i n i n g 50 ml. of b u f f e r (two samples of each b u f f e r are used). The b o t t l e s are suspended i n a water bath maintained at 37\u00C2\u00B0C and r o t a t e d so as to provide good mixing f o r a per i o d of twenty-four hours. At the end .of t h i s p e r i o d , the s o l u t i o n s are f i l t e r e d q u i c k l y , d i l u t e d i f necessary w i t h the b u f f e r and assayed spectro-p h o t o m e t r i c a l l y . R e s u l t s - The s o l u b i l i t y curve (Figure 1 ) , drawn from the data obtained, showed that the s o l u b i l i t y of phenylbutazone i s very low i n b u f f e r s of low pH value s . However, once the pH value reached 6, the s o l u b i l i t y i ncreased g r e a t l y . (b) Determination of the I s o s b e s t i c P o i n t The i s o s b e s t i c point of a s o l u t i o n i s the wave-le n g t h at which changes i n the pH of the s o l u t i o n do not a f f e c t the absorbancy (As) reading of the s o l u t i o n . Since the c o n d i t i o n s of t h i s d i s s o l u t i o n t e s t i n v o l v e a change from an a c i d i c to a basic medium, the wavelength at which absorbancy readings are to be recorded must be at the i s o s b e s t i c p o i n t . Procedure - Weigh a c c u r a t e l y 100 mg. of phenyl-butazone powder and d i s s o l v e ^ i n 100 ml. of 95% ethanol. Ten ml. a l i q u o t s of t h i s s o l u t i o n are d i l u t e d a c c u r a t e l y to 1000 ml. w i t h b u f f e r s of va r i o u s pH values (ranging from pH 1.2 to pH 7.5)'. The spectrum of these s o l u t i o n s are recorded on a rec o r d i n g spectrophotometer (Spectronic 505, Bausch and Lomb). From the spectra of the s o l u t i o n s , 30 an i s o s b e s t i c p o i n t was observed at between 238 mu and 245 mu. The absorbancy of these s o l u t i o n s are then read on a Beckman DU spectrophotometer from 238 mu to 245 mu w i t h each s o l u t i o n blanked against the r e s p e c t i v e b u f f e r . A p l o t of the absorbancy readings f o r the s o l u t i o n s showed t h a t the wavelength that i s c l o s e s t to being the i s o s b e s t i c - point f o r phenylbutazone i s 240 mu (Figure 2 ) . This point was chosen as the wavelength at which a l l subsequent absorbancy readings were recorded. (c) Determination of the A b s o r p t i v i t y Value The a b s o r p t i v i t y ( a s ) i s a constant f o r a p a r t i c u l a r s o l u t e i n a p a r t i c u l a r solvent at a c e r t a i n wavelength. According to Beer's Law, i t i s the slope of the l i n e r e l a t i n g the absorbancy of a s o l u t i o n and i t s c o n c e n t r a t i o n . As = a sbc where As i s the absorbancy of the s o l u t i o n a s i s the a b s o r p t i v i t y b i s the c e l l l e n g t h i n cm. c i s the concen t r a t i o n i n gm./L. Procedure -.Weigh a c c u r a t e l y 100 mg. phenylbutazone poxtfder and d i s s o l v e i n 100 ml. of 95% ethanol. D i l u t e a l i q u o t s of f i v e to twenty ml. to 1000 ml. w i t h Simulated I n t e s t i n a l F l u i d U.S.P. The absorbancy of each s o l u t i o n i s read on a Beckman DU spectrophotometer at 240 mu, using Simulated I n t e s t i n a l F l u i d U.S.P. as a blank. 31 R e s u l t s - The absorbancy readings were p l o t t e d and a s t r a i g h t l i n e was obtained. The a b s o r p t i v i t y was c a l c u l a t e d from the slope of t h i s l i n e and found to be 41.5 (Figure 3 ) . 3 2 2 4 0 2 4 3 2 4 6 0 Wavelength (mu) Figure 2 . The Isosbestic Point of Phenylbutazone 34 0.80 0.60 % 0.40 0.20 As= a sbc a q - As = 41.5 5 10 15 20 Concentration (mg./L.) F i g u r e 3. C a l i b r a t i o n Curve f o r Phenylbutazone i n Simulated I n t e s t i n a l F l u i d at 240 mu 35 IV. THE OPERATING CHARACTERISTICS OF A CONTINUOUS FLOW DISSOLUTION APPARATUS (a) D e s c r i p t i o n of the Apparatus The d i s s o l u t i o n v e s s e l (a o n e - l i t r e three-neck round-bottom f l a s k ) i s immersed i n a constant temperature o o water bath at 37 C t 0 . 5 C. Dipping i n t o the c e n t r a l neck of the f l a s k i s the shaft of a F i s h e r Stedi-Speed adj u s t a b l e s t i r r e r (Model 12) with a four-blade i m p e l l e r blade (3 cm. i n diameter) and a c y l i n d r i c a l wire basket at i t s bottom. The basket which i s A cm. long and 2 . 5 cm. i n diameter i s made from 10-mesh s t a i n l e s s s t e e l wire c l o t h . A g l a s s tube which a c t s as the i n l e t tube f o r the d i s s o l u t i o n medium dips through the r i g h t side neck i n t o the d i s s o l u t i o n v e s s e l to a depth of 10 cm. Connected to t h i s tube i s a two-way stop cork, one arm of which i s connected to a r e s e r v o i r of simulated g a s t r i c j u i c e (2 gm. NaCl + 7 ml. HCl i n 1000 ml. d i s t i l l e d water, pH 1 .2) w h i l e the other arm i s j o i n e d to a r e s e r v o i r of simulated i n t e s t i n a l j u i c e ( 6 . 8 gm. KH 2 P0^ + 1 .52 gm. NaOH i n 1000 ml. d i s t i l l e d water, pH 7 . 5 ). Both r e s e r v o i r s of d i s s o l u t i o n medium are placed on heaters to keep the s o l u t i o n at 37\u00C2\u00B0C 0 . 5 \u00C2\u00B0 C An i n v e r t e d s i n t e r e d g l a s s funnel (30 ml. capacity) of coarse p o r o s i t y dips i n t o the l e f t side arm of the d i s s o l -u t i o n v e s s e l . I t i s j o i n e d to a short l e n g t h of g l a s s tube c a r r y i n g a s i n t e r e d t i p (coarse p o r o s i t y ) , that dips i n t o the d i s s o l u t i o n v e s s e l to a depth of '5.0 cm. A combination g l a s s e l e c t r o d e (not i l l u s t r a t e d i n F i g u r e 4) l e a d i n g from a reco r d i n g potentiometer (Potent-iograph E336A) and a short piece of g l a s s tube, which ac t s as the o u t l e t tube, dip i n t o the broad end of the s i n t e r e d g l a s s f u n n e l . The o u t l e t tube i s j o i n e d by Tygon tubing to an a d j u s t a b l e pump (Cole Palmer A-769) from which tubing leads to a fl o w c e l l (1 cm. i n length) i n a rec o r d i n g spectro-photometer (Spectronic 505, Bausch & Lomb). A recorder ( V a r i c o r d Model 43) i s attached to the spectrophotometer f o r a d i r e c t r e c o r d i n g of the concentration of the s o l u t i o n passing through the flow c e l l . From the fl o w c e l l , the s o l u t i o n i s d e l i v e r e d i n t o a t w e l v e - l i t r e covered g l a s s v e s s e l , that a c t s as the c o l l e c t i n g v e s s e l . (b) C a l i b r a t i o n of the Recorder Procedure - The recorder i s set on the 25 and mV range. I t i s zeroed w i t h g a s t r i c j u i c e i n the sample c e l l and a i r as the blank. S o l u t i o n s of known concent r a t i o n of phenyl-butazone are read i n the sample c e l l of the spectrophotometer at 240 mu and the chart readings on the recorder s c a l e are recorded. From the known concentrations and the chart readings on the recorder s c a l e , a graph i s p l o t t e d (Figure 5 ) . gure 4. Diagram of Continuous Flow D i s s o l u t i o n Apparatus ISPECTRONIC 5Q5 \u00E2\u0080\u00A2 t DISCHARGE COLE PALMER A - 7 6 9 ADOUSTABLE PUMP t FILTERING DEVICE FOR CONTINUOUS FLOW SINTERED GLASS FUNNEL (COARSE 30 mi.) SINTERED TIP (COARSE) VARICORD MODEL FISHER STEDI* SPEED STIRRER TO STIRRING SUCTION / SHAFT T \u00C2\u00A3 S T F U J | D x GLASS TUBE TWO WAY STOPCOCK TEST FLUID H GLASS TUBE ONE LITER FLASK BASKET 38 150 to \u00E2\u0080\u00A2H Ti crj CD ca \u00E2\u0080\u00A2p u crj X ! o 100 10 20 Concentration (mg. phenylbutazone/L^) F i g u r e 5. C a l i b r a t i o n Curve f o r Recorder E x t e r n a l to the Spectronic 505 (c) The E f f e c t of S t i r r i n g Rate on D i s s o l u t i o n The s t i r r i n g r a t e has been reported by many researchers (8, 11, 17) to have a considerable e f f e c t on the d i s s o l u t i o n r a t e . Levy (11) has s t a t e d that too i n t e n s i v e an a g i t a t i o n r a t e i s to be avoided since X-ray photographs have shown tha t t a b l e t p a r t i c l e s tend to remain as an aggregate on the stomach surface. This i m p l i e s that the mixing process i n the stomach i s very low. However, i n the small i n t e s t i n e , the p a r t i c l e s appeared to be very w e l l dispersed i n d i c a t i n g that the mixing i n t h i s r e g i o n i s quite vigorous. Since phenylbutazone i s n e a r l y i n s o l u b l e i n s o l u -t i o n s of pH 1.2 but very s o l u b l e i n s o l u t i o n s of pH 7.5, i t would appear that the absorption of phenylbutazone occurs mainly under the b a s i c c o n d i t i o n s of the small i n t e s t i n e . Hence, a s t i r r i n g r a t e that causes the drug p a r t i c l e s to be w e l l dispersed throughout the medium may be d e s i r a b l e i n the d i s s o l u t i o n t e s t under study. Consequently, s t i r r i n g r a t e s of 65, 100 and 115 r.p.m. i n the forward d i r e c t i o n were i n v e s t i g a t e d using the designed d i s s o l u t i o n apparatus and t e s t procedure. These s t i r r i n g r a t e s were i n v e s t i g a t e d w i t h the s t i r r e r at d i f f e r -ent depths i n the d i s s o l u t i o n medium, using B u t a z o l i d i n t a b l e t s as the t e s t p r e p a r a t i o n , and at a constant pumping ra t e of 60 ml./minute. Each r a t e was t e s t e d i n d u p l i c a t e . 40 R e s u l t s - The data obtained from the d i s s o l u t i o n runs are t a b u l a t e d i n Table I . I t can be seen th a t when the s t i r r i n g i s not enough to move the p a r t i c l e s , the r e l e a s e r a t e of the drug i s low even though the s o l u t i o n i n the d i s s o l u t i o n v e s s e l appears to be homogeneous. The low rel e a s e r a t e i s due t o the f a c t that the t a b l e t p a r t i c l e s remain as an aggregate on the d i s s o l u t i o n v e s s e l bottom, thus present-i n g a l i m i t e d surface area to the d i s s o l u t i o n medium. When the basket i s 6 Cm. from the v e s s e l bottom, the s t i r r i n g i s i n s u f f i c i e n t even at the high s t i r r i n g r a t e of 115 r.p.m. At 3.5 cm. from the bottom of the v e s s e l , the s t i r r i n g i s adequate except at the lox^est r a t e of 65 r.p.m., when about h a l f of the t a b l e t p a r t i c l e s remain aggregated on the v e s s e l bottom. The other two s t i r r i n g r a t e s caused the p a r t i c l e s to move through the medium, the higher ra t e of 115 r.p.m. g i v i n g a more vigorous movement. At a depth of 1 cm. from the v e s s e l bottom, the s t i r r i n g e f f e c t i s qui t e vigorous even at the r a t e of 65 r.p.m. To avoid t h i s s t i r r i n g e f f e c t , t h i s depth was not chosen f o r product t e s t i n g . The depth f i n a l l y chosen was 3.5 cm. w i t h a s t i r r -i n g r a t e of! 100 r.p.m. r a t h e r than 115 r.p.m. The former r a t e produced the d e s i r e d s t i r r i n g e f f e c t . At t h i s speed, the p a r t i c l e s move sl o w l y through the medium. 41 Table I . The Effect of S t i r r i n g Rate on Dissolution S t i r r i n g rate Depth of basket Mg. phenylbutazone (forward direction) from vessel bottom i n solution i n 3 hours 1 cm. .87.5 mg. 65 r.p.m. 3*5 cm. 62.1 mg. 6 cm. 55.4 mg. 1 cm. 83.1 mg. 100 r.p.m. 3.5 cm. 83.5 mg. 6 cm. 75.0 mg. 115 r.p.m. 1 cm. 3.5 cm. 6 cm. 90.0 mg. 85.0 mg. 78.5 mg. 42 (d) The E f f e c t of Pumping Rate on D i s s o l u t i o n Three pumping r a t e s were stud i e d f o r t h e i r e f f e c t on d i s s o l u t i o n r a t e . The d i s s o l u t i o n t e s t was c a r r i e d out w i t h B u t a z o l i d i n t a b l e t s as the t e s t p r e p a r a t i o n and w i t h the basket at 3.5 cm. fronr the v e s s e l bottom s t i r r i n g at a r a t e of 100 r.p.m. The pumping r a t e s s t u d i e d were 50 ml./min., 60 ml./min. and 70 ml./min. Rates lower than 50 ml./min. were not s t u d i e d due to instrum e n t a l l i m i t a t i o n s i n reading the more concentrated s o l u t i o n s . R e s u l t s - The data obtained are ta b u l a t e d i n Table I I . This data shows that there i s no s i g n i f i c a n t d i f f e r -ence i n the rel e a s e of the drug i n the three-hour p e r i o d . The pH changes i n the medium are a f f e c t e d by the pumping r a t e to a s l i g h t extent. Higher pumping r a t e s gave a much f a s t e r pH change from a c i d i c to bas i c pH. At the pumping r a t e of 60 ml./min., the sharp r i s e i n pH from about pH of 2 to pH of 6 . 2 occurred w i t h i n t w e n t y - f i v e minutes (Figure 6), whi l e at a pumping ra t e of 70 ml./min., i t occurred w i t h i n twenty minutes. However, at 70 ml./min., the f i n a l volume of solvent i s too great to be handled e a s i l y . At 50 ml./min., the pH change occurred i n t h i r t y minutes but at t h i s r a t e , the s o l u t i o n i s becoming too saturated to be read on the spectrophotometer. A pumping rat e of 60 ml'./min. was t h e r e f o r e , f i n a l l y chosen f o r the d i s s o l u t i o n t e s t . 43 Table I I . The E f f e c t of Pumping Rate on D i s s o l u t i o n Pumping r a t e Mg. of phenylbutazone i n s o l u t i o n 1 hour 2 hours 3 hours 50 ml./min. 1. 4.0 mg, 2. 3.9 mg. 56.0 mg, 51.0 mg. 86.5 mg. 86.4 mg. 60 ml./min. 1. 9.0 mg. 2. 8.3 mg. 70 ml./min. 1. 5.9 mg. 2. 6.7 mg. 68.4 mg. 62.6 mg. 62.2 mg. 63.0 mg. 89.6 mg. 86.4 mg, 86.5 mg. 88.2 mg. 45' (e) Test Procedure With the apparatus set up as described and as shown i n F igure 4, the d i s s o l u t i o n v e s s e l ( c o n t a i n i n g one l i t r e of simulated g a s t r i c j u i c e ) i s allowed to e q u i l i b r a t e i n a constant temperature water bath at 37\u00C2\u00B0C + 0.5\u00C2\u00B0C The e n t i r e system i s f l u s h e d out w i t h simulated g a s t r i c j u i c e to remove a i r from the system. The recorder i s zeroed w i t h simulated g a s t r i c j u i c e i n the sample flow c e l l and a i r as the blank. A s i n g l e phenylbutazone t a b l e t (100 mg.) i s put i n t o the wire basket below the i m p e l l e r blade and the whole apparatus i s set infemotion. The s t i r r i n g r a t e i s 100 r.p.m. i n a forward (clockwise) d i r e c t i o n at a depth of 3.5 cm. from the bottom of the d i s s o l u t i o n v e s s e l . With the i n l e t tube from the r e s e r v o i r of simulated g a s t r i c j u i c e opened, the pump i s turned on to d e l i v e r 60 ml./min. through the e n t i r e system. A f t e r the i n i t i a l t h i r t y minutes, simulated i n t e s t -i n a l j u i c e i s allowed i n t o the system. At t h i s p o i n t , the potentiometer i s switched on to record pH changes as the medium i s g r a d u a l l y changed from an a c i d i c medium to a basi c one. A l i q u o t s from the c o l l e c t i n g v e s s e l are taken at hourly i n t e r v a l s f o r a n a l y s i s on a Beckman DU spectrophoto-meter at 240 mu, w i t h simulated i n t e s t i n a l j u i c e as the blank. As the s o l u t i o n from the d i s s o l u t i o n v e s s e l passes 46 through the flow c e l l i n the spectrophotometer set at 240 mu, the V a r i c o r d records the c o n c e n t r a t i o n . This gives a c o n t i n -uous r e c o r d i n g of the c o n c e n t r a t i o n of the s o l u t i o n as d i s s o l u t i o n occurs. The d i s s o l u t i o n run i s c a r r i e d on f o r three to s i x hours depending on the d i s s o l u t i o n rate ! of the i n d i v i -dual products. At the end of each run, the e n t i r e system i s f l u s h e d out w i t h 95% ethanol and water. Using t h i s t e s t procedure, seven brands of commer-i c i a l l y a v a i l a b l e phenylbutazone t a b l e t s (100 mg.) were t e s t e d i n t r i p l i c a t e . Four of the products are sugar-coated t a b l e t s (Products A, E, W, X) while the other three are e n t e r i c coated t a b l e t s (Products AA, CC, DD^). Each product was t e s t e d i n t r i p l i c a t e . (f) R e s u l t s An average continuous c o n c e n t r a t i o n p l o t was obtained f o r each product from the curves drawn out on the recorder. This p l o t gave the d i s s o l u t i o n p r o f i l e of the product and a l s o allows the c a l c u l a t i o n of the t o t a l amount of drug r e l e a s e d i n any p e r i o d of time (Figures 7 a , b, c ) . The h o u r l y a n a l y s i s on the Beckman DU spectrophotometer a l s o gave the amount of drug rel e a s e d at each hourly i n t e r v a l , thus p r o v i d i n g a check on the amount r e g i s t e r e d by the recorder (Table I I I ) . From the data on the products obtained by the two 4 7 L8 LO I-H e o \u00E2\u0080\u00A2H \u00E2\u0080\u00A2P cd U \u00E2\u0080\u00A2P c \u00C2\u00A9 o o o 20 CC 1 2 Time (hours) Figure 7b. D i s s o l u t i o n P r o f i l e s f o r Two Brands of Phenylbutazone Tablets 50 Table I I I . D i s s o l u t i o n Data f o r Seven Brands of Phenylbutazone Tablets Mg. of phenylbutazone i n s o l u t i o n Product 1 hour 2 hours 3 hours 1. 5 . 2 mg. 6 2 . 5 mg. 8 6 . 5 mg. A 2 . 5 . 2 mg. 6 1 . 9 mg. 8 8 . 0 mg. 3 . 5 . 2 mg. 6 5 . 9 mg. 9 3 . 5 mg. 1. 1 .2 mg. 5 2 . 5 mg. 8 6 . 5 mg. E 2 . 1 . 8 mg. 5 0 . 4 mg. 81 . 8 mg. 3 . 1.5 mg. 4 8 . 0 mg. 7 9 . 2 mg. 1. 0 . 8 mg. 4 3 . 2 mg. 8 5 . 3 mg. AA 2 . 0 . 8 mg. 4 3 . 2 mg. 8 6 . 5 mg. 3 . 1 .2 mg. 51-5 mg. 8 9 . 6 mg. 1. 1 .4 mg. 9 1 . 4 mg. 9 6 . 2 mg. CC 2 . 1 .7 mg. 9 5 . 7 mg. 1 0 0 . 0 mg. 3 . 1 .7 mg. 9 0 . 7 mg. 9 5 . 8 mg. 51 Table I I I (Continued) Mg. of phenylbutazone i n s o l u t i o n Product 3 hours 4 hours 5 hours 6 hours 1. 7 . 4 mg. 2 3 . 6 mg. 5 5 . 8 mg. 7 5 . 7 mg. X 2 . 1 6 . 2 mg. 5 5 . 3 mg. 7 8 . 7 mg. 9 3 . 0 mg. 3 . 2 3 . 8 mg. 5 0 . 8 mg. 7 5 . 0 mg. 9 2 . 2 mg. 1. 3 6 . 0 mg. 5 5 . 2 mg. 70 . 6 mg. 8 6 . 3 mg. W 2 . 3 6 . 2 mg. 5 5 . 0 mg. 70 .3 mg. 8 6 . 0 mg. 3 . 3 6 . 3 mg. 5 5 . 3 mg. 70 . 5 mg. 8 6 . 2 mg. 1. 5 . 4 mg. 2 7 . 0 mg. 9 4 . 0 mg. 101 .5 mg. DDX 2 . 4 . 5 mg. 2 2 . 5 mg. 9 1 . 7 mg. 9 9 . 0 mg. 3 . 4 . 5 mg. 2 2 . 3 mg. 9 0 . 9 mg. 9 3 . 0 mg. 52 Table IV. T 5 0 % a n d T 9 0 % Values f o r Seven Phenylbutazone Tablets Brands of Product T $ 0 $ value T 9 0 % value A 100 minutes 180 minutes E 120 minutes 215 minutes W 225 minutes 735 minutes. X 255 minutes 735 minutes AA 125 minutes 185 minutes CC 80 minutes 120 minutes DD-L 225 minutes 300 minutes 53 methods, time f o r 5 0 $ of the drug (T5Q$) and 9 0 $ of the drug (T^ 0^) to go i n t o s o l u t i o n was c a l c u l a t e d and t a b u l a t e d i n Table IV. The four brands of sugar-coated t a b l e t s showed l i t t l e d i s s o l u t i o n i n simulated g a s t r i c f l u i d . However, once the medium reached a pH of 6.2, the co n c e n t r a t i o n of the a c t i v e i n g r e d i e n t increased g r e a t l y . This change i n pH occurred i n twenty-five minutes at the pumping rat e of 60 ml./minute. Products A and E (which d i s i n t e g r a t e d w i t h i n f i f t e e n minutes of the s t a r t of the experiment) showed s i m i l a r d i s s o l u t i o n p a t t e r n s . The c o n c e n t r a t i o n of a c t i v e i n g r e d i e n t continued to increase g r a d u a l l y once the medium reached a pH of 6. A peak was reached i n about one and a h a l f hours. The curve then g r a d u a l l y d e c l i n e d due to a d i l u t i o n process by the incoming s o l v e n t . Product E rele a s e d s l i g h t l y l e s s a c t i v e i n g r e d i e n t from the t a b l e t than d i d Product A. The other two sugar-coated products showed d i f f e r -ent d i s s o l u t i o n p r o f i l e s due to the l a c k of d i s i n t e g r a t i o n . Product W d i d not d i s i n t e g r a t e at a l l even at the end of s i x hours. D i s s o l u t i o n by t h i s product was very low and stayed at the same l e v e l throughout the e n t i r e d i s s o l u t i o n run. The a c t i v e i n g r e d i e n t seemed to d i s s o l v e out from the surface of the t a b l e t , which was smaller but s t i l l i n t a c t 5k at the end of the d i s s o l u t i o n run. Product W showed very l i t t l e \u00E2\u0080\u00A2 t a b l e t v a r i a t i o n . Product X was found to vary from one t a b l e t to another i n the same l o t . A f t e r t h e . t a b l e t c o a t i n g came o f f a f t e r three hours, l a r g e p a r t i c l e s could be'seen coming o f f and,,at t h i s p o i n t , the con c e n t r a t i o n of the a c t i v e i n g r e d i e n t r e g i s t e r e d on the recorder was seen to increase suddenly but not g r e a t l y . The concen t r a t i o n l e v e l remained approximately the same f o r about an hour, then decreased very s l i g h t l y f o r the r e s t of the time. The d i s s o l u t i o n rate of Products \u00C2\u00A5 and X was so low t h a t the d i s s o l u t i o n - r u n had to be c a r r i e d on f o r s i x hours i n s t e a d of three hours. Products A and E re l e a s e d about 90% of the a c t i v e i n g r e d i e n t i n three hours while i t took Products W and X s i x hours to r e l e a s e the same amount of a c t i v e i n g r e d i e n t . The three e n t e r i c coated Products AA, CC and DD-^ remained i n t a c t t i l l the d i s s o l u t i o n medium reached a pH of 7. Products AA and CC broke up very q u i c k l y i n t o small p a r t i c l e s . Product DD^ d i d not s t a r t to d i s i n t e g r a t e u n t i l about three and a h a l f hours a f t e r the s t a r t of the d i s s o l u -t i o n run. Product CC gave a much f a s t e r d i s s o l u t i o n r a t e than Product AA, wi t h a' concentration peak much higher than those of the other t e s t products and, even e a r l i e r than the sugar-coated products. This was probably due to i t s 55 almost immediate d i s i n t e g r a t i o n i n the a l k a l i n e medium i n t o very f i n e p a r t i c l e s . The d i s s o l u t i o n p r o f i l e f o r Product AA was s i m i l a r to those f o r the sugar-coated Products A and E , except f o r a delay of about twenty-five minutes i n i t s peak due to the e n t e r i c c o a t i n g . The f a l l i n the d i s s o l u t i o n curve of Product CC was very sharp while that of Product AA was much more gradual. Product DD]_ released i t s a c t i v e ingred-i e n t r a p i d l y a f t e r d i s i n t e g r a t i o n occurred, g i v i n g a peak second only to Product CC. Henee, i t would appear that the d i s i n t e g r a t i o n time of the t a b l e t had an e f f e c t on the d i s s o l u t i o n of the t a b l e t when the d i s i n t e g r a t i o n time was e x c e s s i v e l y l o n g . A T^Q^ value of 120 minutes would seem to be a reasonable l i m i t of acceptance of the products th a t could be s a i d to be e f f e c t i v e \" i n v i v o \" . This i m p l i e s that only f o u r of the products t e s t e d , A, E, AA and CC are acceptable. This \" i n v i t r o \" e s t i m a t i o n can be supported by the \" i n v i v o \" data that showed the three Prdducts E , AA and CC were at l e a s t 75$ as e f f e c t i v e as Product A (a product t e s t e d and found to give good c l i n i c a l response). Product. AA would be a b o r d e r - l i n e case by both the \" i n v i v o \" and the \" i n v i t r o \" r e s u l t s . 56 V. THE \"IN VIVO\" CHARACTERISTICS OF PHENYLBUTAZONE TABLETS Burns and h i s co-workers (2) claimed that due t o the a f f i n i t y of phenylbutazone f o r plasma p r o t e i n s as compared t o t i s s u e p r o t e i n s , a great p o r t i o n of administered phenylbutazone i s found i n the plasma. They reported that peak plasma l e v e l s were reached i n about two hours a f t e r o r a l a d m i n i s t r a t i o n , i n d i c a t i n g that the drug was r a p i d l y absorbed from the g a s t r o i n t e s t i n a l t r a c t . Plasma l e v e l s d i d not increase p r o p o r t i o n a t e l y w i t h i n c r e a s i n g doses of the drug but tend to. reach a l i m i t i n g c o n c e n t r a t i o n , which v a r i e d c o n s i d e r a b l y among s u b j e c t s . On repeated d a i l y dosage, the drug.accumulated i n the body w i t h a progressive increase i n the plasma co n c e n t r a t i o n u n t i l a pla t e a u was reached on the t h i r d or f o u r t h day. In a comparative study of com m e r i c i a l l y a v a i l a b l e brands of phenylbutazone t a b l e t s , S e a r l and Pernarowski (26) determined serum l e v e l s a f t e r a d m i n i s t r a t i o n of the products; to human s u b j e c t s . The seven products were administered to nine subjects as shown i n Table V. Each subject was given two t a b l e t s , that i s approximately 200 mg. of phenylbutazone. I n general, the product was given to the subject s h o r t l y a f t e r b r e a k f a s t . Three t o f i v e samples of blood were taken over a 43-hour p e r i o d but only the r e s u l t s to 30 hours are shown. 57 Determination of Phenylbutazone i n Serum F i f t e e n ml. of blood are withdrawn by means of a dry s t e r i l e syringe and needle from a l a r g e v e i n i n the bend of the elbow. The blood i s allowed to c l o t , then c e n t r i f u g e d and the serum i s removed. Two ml. of serum are t r a n s f e r r e d to a 5 0-ml. glass-stoppered c e n t r i f u g e tube. F i v e ml. of 3 N.HC1- s o l u t i o n and 2 0 . 0 ml. of heptane are added and the tube i s shaken f o r t h i r t y minutes i n an auto-matic shaker and c e n t r i f u g e d at 1 2 0 0 r.p.m. f o r f i v e minutes. F i f t e e n , m l . of heptane are withdrawn and t r a n s f e r r e d to a 2.00-ml. b o t t l e . F i v e ml. of 2 . 5 N.NaOH s o l u t i o n are added and s w i r l e d g e n t l y . The s o l u t i o n i s then shaken f o r f i v e minutes and poured i n t o a 5 0-ml. c e n t r i f u g e tube and ce n t r i f u g e d at 1 2 0 0 r.p.m. f o r three minutes. The absorbancy of the sodium hydroxide s o l u t i o n i s read at 2 6 5 mu. The a b s o r p t i v i t y of phenylbutazone at 2 6 5 mu i n 2 . 5 N.NaOH i s 6 5 . 2 . I t may be necessary to d i l u t e the sodium hydroxide s o l u t i o n or to decrease the amount of serum taken f o r a n a l y s i s i f the concent r a t i o n of phenylbutazone i n the serum exceeds 3 0 mg. per l i t r e . A blood sample taken before the a d m i n i s t r a t i o n of the drug serves as a c o n t r o l or \"blood-blank\". This sample when t r e a t e d as described above, absorbs some u l t r a v i o l e t r a d i a n t energy at 2 6 5 mu. Consequently, a l l subsequent assay values must be adjusted to compensate f o r t h i s \"blood-blank\". 58 R e s u l t s Peak plasma l e v e l s were obtained i n f i v e r a t h e r than i n two hours as had been reported by Burns and h i s co-workers ( 2 ) . A t y p i c a l blood curve i s shown i n Figure 8. A f t e r the peak r e g i o n , the serum drug l e v e l decreased q u i t e g r a d u a l l y . The areas under the blood curves were determined by a planimeter and are t a b u l a t e d i n Table V. Using Product A as a chosen standard, only three other products, E, AA and CC appeared to be at l e a s t 75% as e f f e c t i v e as Product A, and thus considered acceptable. Since data f o r subjects 3 - 9 was incomplete, i t was not p o s s i b l e t o use i t f o r a comparison. However, a v a i l a b l e data from these subjects tend to i n d i c a t e that response to the products f o l l o w the same trend as i n subjects 1 and 2. 10 20 Time (hours) Figure 8. Concentration of Phenylbutazone i n Serum a f t e r A d m i n i s t r a t i o n u! of Product A to Subject 1 60 Table V. Areas under Blood Curves f o r Seven Brands of Phenylbutazone Ta b l e t s ^sProduct Sub j e c t N v A E W X AA CC DD]_ 1 18.57 14.8 1.82 13.3 12.42 15.33 6.55 2 20.55 15.2 4.61 7.0 15.51 22.84 11.21 3 24.1 26.4 8.9 17.0 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 4 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 8.62 \u00E2\u0080\u0094 \u00E2\u0080\u0094 5 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 10.48 \u00E2\u0080\u0094 \u00E2\u0080\u0094 6 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 23.34 \u00E2\u0080\u0094 7 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u00A2 \u00E2\u0080\u0094 11.48 \u00E2\u0080\u0094 8 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 3.79 9 \u00E2\u0080\u0094 . \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u00A2 \u00E2\u0080\u0094 \u00E2\u0080\u0094 4.65 61 V I \u00C2\u00AB \"IN VIVO\" - \"IN VITRO\" CORRELATION \"In v i t r o \" r e s u l t s only serve to reduce the number of samples considered s u i t a b l e f o r \" i n v i v o \" t e s t i n g . However, they are s i g n i f i c a n t when they can be q u a n t i t a t i v e l y c o r r e l a t e d w i t h \" i n v i v o \" data. Even though the \" i n v i v o \" data a v a i l a b l e i s not complete f o r a l l t e s t products, an attempt was made to c o r r e l a t e t h i s data w i t h the T^Q^ and the T^Q^ values obtained by the \" i n v i t r o \" t e s t procedure. C o r r e l a t i o n was attempted only f o r the two subjects w i t h complete \" i n v i v o \" data, since data f o r Product A was not a v a i l a b l e f o r the other s u b j e c t s . However, the response shown by these subjects seem to f o l l o w the same trend as tha t of subjects 1 and 2. I t can be assumed, t h e r e f o r e , t h a t the same type of c o r r e l a t i o n could be obtained f o r these s u b j e c t s , t a k i n g i n t o account the p o s s i b l e d i f f e r e n c e s i n the metabolism of the drug i n these s u b j e c t s . By the use of l i n e a r r e g r e s s i o n , the l i n e of \" l e a s t squares\" drawn f o r each set of data f o r subjects 1 and 2 (Figures 9, 10, 11, 12). The p o i n t s f o r subject 2 seem to f i t b e t t e r on the l i n e of \" l e a s t squares\" drawn than those f o r subject 1. One of the reasons f o r the d e v i a t i o n s from the \" l e a s t squares\" l i n e could be th a t some of the \" i n v i v o \" blood curves were drawn from the inadequate data. Tablet v a r i a b i l i t y ( e s p e c i a l l y f o r Product X) could a l s o have c o n t r i b u t e d to the d e v i a t i o n s . 62 The l i n e s of \" l e a s t squares\" had negative slopes i n d i c a t i n g an in v e r s e r e l a t i o n s h i p between the \" i n v i v o \" and the \" i n v i t r o \" data. The slopes of these l i n e s ranged from -0.042, to -0.075 5 w i t h the slopes of the T^Q^ l i n e s greater than the T^Q^ l i n e s of both s u b j e c t s . The slopes of the l i n e s f o r subject 2 were greater than those of subject 1. Th i s was expected since subject 2 showed greater response to the drug than subject 1. The d i f f e r e n c e between the slopes of the' T^Q$ l i n e and the T^Q$ l i n e of subject 1 was twice t h a t of subject 2. 64 66 67 V I I . DISCUSSION The d i s s o l u t i o n procedure described h e r e i n i s completely automatic. No r o u t i n e a n a l y s i s of the medium i s r e q u i r e d , because a complete re c o r d i n g of the amount of the a c t i v e i n g r e d i e n t r e l e a s e d from the t a b l e t throughout the d i s s o l u t i o n process i s obtained on the recorder. Determination of the t o t a l area under the recorded curve w i l l give the t o t a l amount of drug r e l e a s e d . At the same time, a complete r e c o r d i n g of the pH changes i n the d i s s o l u t i o n medium can be obtained on a re c o r d i n g potentiometer. This r e c o r d i n g enables one to see how the d i s s o l u t i o n process i s a f f e c t e d by the changing pH of the d i s s o l u t i o n medium. A s i n g l e a n a l y s i s of the c o l l e c t e d medium w i l l a l s o give the t o t a l amount of drug r e l e a s e d i n a p e r i o d of time but i t w i l l not give the d i s s o l u t i o n time f o r a spec-i f i e d amount of drug t o go i n t o s o l u t i o n . F u r t h e r , t h i s f i n a l a n a l y s i s does not give the d i s s o l u t i o n p r o f i l e which can be seen to vary from product to product. Even though the apparatus set-up seems to i n v o l v e many components, the b a s i c p a r t s r e q u i r e d f o r the continuous f l o w system are the r e s e r v o i r s of d i s s o l u t i o n medium, the d i s s o l u t i o n v e s s e l , the pump and the c o l l e c t i n g v e s s e l . The re c o r d i n g potentiometer and the spectrophotometer w i t h i t s attached recorder are ac c e s s o r i e s that f u r n i s h more inform-a t i o n and avo i d manual a n a l y s i s of the medium. These 68 a c c e s s o r i e s are not necessary i f one i s i n t e r e s t e d i n the t o t a l amount of drug r e l e a s e d i n a c e r t a i n p e r i o d of time. The b a s i c p a r t s of t h i s d i s s o l u t i o n apparatus are r e l a t i v e l y easy to o b t a i n and assemble and provide a good reproducible method of checking on product q u a l i t y . The inverse r e l a t i o n s h i p e s t a b l i s h e d between the \" i n v i v o \" and the \" i n v i t r o \" data obtained by t h i s t e s t procedure tends to i n d i c a t e that t h i s procedure may p o s s i b l y be used i n the p r e d i c t i o n of the \" i n v i v o \" a v a i l a b i l i t y of the a c t i v e i n g r e d i e n t from the s o l i d dosage form. A T^Q% value of 120 minutes as the l i m i t of acceptance f o r the products seems reasonable on the b a s i s of both the \" i n v i v o \" and the \" i n v i t r o \" data. From the \" l e a s t squares\" l i n e s , i t would seem that products w i t h a T^0% value of more than f i v e hours would not be absorbed i n t o the blood stream at a l l . From both the \" i n v i v o \" and the \" i n v i t r o \" data, only f o u r of the seven products t e s t e d , namely A, E, AA and CC, can be accepted as products that w i l l be e f f e c t i v e when administered to p a t i e n t s . Products W and X give such low serum l e v e l s and long T^Q^ values t h a t one can conclude t h a t these products are u n s a t i s f a c t o r y and should not be administered to p a t i e n t s . Product DD^ w i t h s l i g h t l y higher serum l e v e l s i s s t i l l u n s a t i s f a c t o r y . The poor \" i n v i v o \" r e l e a s e from these products i s most probably due to poor f o r m u l a t i o n , which.is revealed by t h e i r poor d i s i n t e g r a t i o n . c h a r a c t e r i s t i c s . Product W and X do not d i s i n t e g r a t e w h i l the d i s i n t e g r a t i o n time of Product DD-j_ i s abnormally long 70 V I I I . SUMMARY In t h i s i n v e s t i g a t i o n , a completely automatic continuous f l o w d i s s o l u t i o n procedure was developed and t e s t e d . P e r t i n e n t c o n d i t i o n s of d i s s o l u t i o n were studi e d and chosen to t e s t seven brands of commericially a v a i l a b l e phenylbutazone t a b l e t s . \"In v i v o \" s t u d i e s were c a r r i e d out on these products by determining serum l e v e l s a f t e r the a d m i n i s t r a t i o n of the products to nine s u b j e c t s . From the \" i n v i t r o \" data obtained by the t e s t d i s s o l u t i o n procedure, a T^Q$ v a l u e \u00C2\u00B0f 120 minutes was chosen as the l i m i t of acceptance f o r the t e s t products. Of the seven t e s t products, only f o u r were acceptable on the b a s i s of both the \" i n v i v o \" and the \" i n v i t r o \" data. C o r r e l a t i o n of the \" i n v i v o \" and the \" i n v i t r o \" data r e s u l t e d i n \" l e a s t squares\" l i n e s w i t h negative slopes. This c o r r e l a t i o n i n d i c a t e d the p o s s i b i l i t y of usi n g t h i s \" i n v i t r o \" d i s s o l u t i o n procedure i n the p r e d i c t i o n of the \" i n v i v o \" a v a i l a b i l i t y of phenylbutazone from the s o l i d dosage form. 71 IX. BIBLIOGRAPHY 1. Brudney, N., Stewart, D.J. and Eustace, B.T. : Canad. Med. Ass. J . , 90 : 980 (1964). 2. Burns, J . J . , Rose, R.K., Chenkin, T., Goldman', A., S c h u l e r t , A., and Brodie, B.B. : J . Pharmacol. 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J . , 97 : 493 ( 1 9 6 4 ) . "@en . "Thesis/Dissertation"@en . "10.14288/1.0104187"@en . "eng"@en . "Pharmaceutical Sciences"@en . "Vancouver : University of British Columbia Library"@en . "University of British Columbia"@en . "For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use."@en . "Graduate"@en . "Biopharmaceutical properties of solid dosage form"@en . "Text"@en . "http://hdl.handle.net/2429/35725"@en .