VOLUME 6 5 , NO. 1, JANUARY/FEBRUARY 2 0 0 4 Bioequivalence Study o f T w o Formulations o f Enalapril, at a Single Oral Dose o f 20 mg (Tablets): A Randomized, T w o - W a y , Open-Label, Crossover Study in H e a l t h y Volunteers A n t o n i o Portol~s, M D , PhD, 1 A n a Terleira, M D , PhD, 1 Susana A l m e i d a , P h a r m D , 2 M a r Garcfa-Arenillas, M D , PhD, ~ M a r i - C r u z Caturla, PhD, 3 A u g u s t Filipe, M D , MSc, 2 and Emilio Vargas, M D , PhD ~ Z Unidad de Estudios de Farmacologfa Clfnica, Servicio de Farmacologfa, Clfnica Hospital Clfnico San Carlos, Madrid, Spain, 2Medical Department, Tecnimede Sociedade Tdcnico-Medicinal S.A., Prior Velho, Portugal, and 3MCC Analftica, Barcelona, Spain A B S T R A C T Background: Enalapril m a l e a t e is t h e m o n o e t h y l e s t e r p r o d r u g of enalapril- at, a n a n g i o t e n s i n - c o n v e r t i n g e n z y m e i n h i b i t o r i n d i c a t e d in t h e m a n a g e m e n t of e s s e n t i a l a n d r e n o v a s c u l a r h y p e r t e n s i o n , a n d in t h e t r e a t m e n t of c o n g e s t i v e h e a r t f a i l u r e a n d in a s y m p t o m a t i c p a t i e n t s w i t h left v e n t r i c u l a r d y s f u n c t i o n a n d a n e j e c t i o n f r a c t i o n of ->35%. Enalapril h a s little p h a r m a c o l o g i c a c t i v i t y until h y d r o l y z e d in v i v o t o e n a l a p r i l a t . Objective: T h e a i m of t h e p r e s e n t s t u d y w a s t o c o m p a r e t h e b i o a v a i l a b i l i t y a n d t o l e r a b i l i t y of 2 c o m m e r c i a l b r a n d s ( t e s t a n d r e f e r e n c e f o r m u l a t i o n s ) of e n a l a p r i l t a b l e t s (20 mg), d e s c r i b e d as t h e r a t e a n d e x t e n t of a b s o r p t i o n of t h e a c t i v e m o i e t y , t o a s s e s s t h e i r b i o e q u i v a l e n c e . Methods: This s i n g l e - d o s e , r a n d o m i z e d , 2-way, open-label, c r o s s o v e r s t u d y in h e a l t h y v o l u n t e e r s a g e d 18 t o 40 y e a r s w a s c o n d u c t e d a t t h e Clinical Phar- m a c o l o g y S t u d y Unit, H o s p i t a l Clfnico San Carlos (Madrid, Spain). S u b j e c t s w e r e r a n d o m i z e d t o r e c e i v e ( u n d e r f a s t i n g c o n d i t i o n s ) e i t h e r t h e t e s t o r refer- e n c e f o r m u l a t i o n of e n a l a p r i l (20-mg t a b l e t ) at s t u d y p e r i o d 1 a n d t h e o p p o s i t e f o r m u l a t i o n a t s t u d y p e r i o d 2. S t u d y p e r i o d s w e r e s e p a r a t e d b y a w a s h o u t p e r i o d of at l e a s t 7 d a y s . During e a c h s t u d y p e r i o d , 15 p l a s m a e x t r a c t i o n s w e r e m a d e t o d e t e r m i n e e n a l a p r i l a n d e n a l a p r i l a t p l a s m a c o n c e n t r a t i o n s a n d t o cal- c u l a t e t h e p h a r m a c o k i n e t i c (PK) p r o p e r t i e s ( m a x i m a l p l a s m a d r u g c o n c e n t r a - t i o n [C . . . . . ] , t i m e t o C . . . . . [ T . . . . . ], a r e a u n d e r t h e p l a s m a c o n c e n t r a t i o n - t i m e c u r v e [AUC] t o t h e l a s t m e a s u r a b l e c o n c e n t r a t i o n [AUCt], AUC f r o m t i m e 0 t o i n f i n i t y [AUC0_~], m e a n r e s i d e n c e time, a n d e l i m i n a t i o n half-life [tl/2] ) of b o t h . P h y s i c a l e x a m i n a t i o n , s u b j e c t i n t e r v i e w , l a b o r a t o r y a n a l y s e s , e l e c t r o c a r - d i o g r a m , a n d b l o o d p r e s s u r e (BP) w e r e u s e d t o a s s e s s t o l e r a b i l i t y . Accepted for publication November 21, 2003. Printed in the USA. Reproduction in whole or part is not permitted. 0011-393X/04/$19.00 34 Copyright © 2004 Excerpta Medica, Inc.
A. Portol~s et aL Results: T w e n t y - f o u r s u b j e c t s w e r e i n c l u d e d i n t h e s t u d y (12 m e n , 12 w o m e n ; m e a n [SD] age, 22.8 [2.2] y e a r s [range, 19-30 y e a r s ] ) . Of t h e s e , 1 s u b j e c t (4.2%) w i t h d r e w f r o m t h e s t u d y f o r p e r s o n a l r e a s o n s ; t h u s , PK a n d s t a t i s t i c a l a n a l y s e s i n c l u d e d r e s u l t s f r o m 23 s u b j e c t s . No s t a t i s t i c a l l y s i g n i f i c a n t s e q u e n c e o r p e r i o d e f f e c t w a s f o u n d . T . . . . w a s n o t s t a t i s t i c a l l y d i f f e r e n t be- t w e e n t h e 2 f o r m u l a t i o n s , a n d t h e 90% CI c a l c u l a t e d f o r T . . . . for t h e d i f f e r e n c e of t h e m e d i a n s w a s w i t h i n t h e p r e d e f i n e d r a n g e . T h e 90% CIs of t h e l o g a r i t h - mically t r a n s f o r m e d c o n c e n t r a t i o n - d e r i v e d p a r a m e t e r s (C . . . . . AUCt, a n d AUC0_~) a l s o w e r e w i t h i n t h e p r e d e f i n e d range; t h u s , t h e 2 f o r m u l a t i o n s a r e c o n s i d e r e d b i o e q u i v a l e n t . For b o t h f o r m u l a t i o n s , s y s t o l i c a n d d i a s t o l i c BPs s h o w e d signifi- c a n t r e d u c t i o n s c o m p a r e d w i t h b a s e l i n e v a l u e s (P < 0.05). Seven a d v e r s e e f f e c t s w e r e r e c o r d e d , all of t h e m t r a n s i e n t a n d n o n e of s e v e r e i n t e n s i t y . Conclusions: In t h i s s t u d y of 2 c o m m e r c i a l b r a n d s ( t e s t a n d r e f e r e n c e for- m u l a t i o n s ) of e n a l a p r i l in h e a l t h y s u b j e c t s , d e s i g n e d a n d c o n d u c t e d u n d e r Good Clinical P r a c t i c e g u i d e l i n e s , a s i m i l a r r a t e a n d e x t e n t of a b s o r p t i o n for b o t h f o r m u l a t i o n s w e r e f o u n d t o b e b i o e q u i v a l e n t . B o t h f o r m u l a t i o n s p r o d u c e d a s i g n i f i c a n t d e c r e a s e in BP v a l u e s a n d w e r e g e n e r a l l y well t o l e r a t e d . (Curr Ther Res Clin Exp. 2004;65:34--46) C o p y r i g h t © 2004 E x c e r p t a Medica, Inc. K e y w o r d s : b i o e q u i v a l e n c e , b i o a v a i l a b i l i t y , p h a r m a c o k i n e t i c s , e n a l a p r i l , e n a l a p r i l a t , h e a l t h y v o l u n t e e r s , clinical trial, b l o o d p r e s s u r e . I N T R O D U C T I O N T h e u s e of g e n e r i c d r u g s is of i n c r e a s i n g i m p o r t a n c e , in t e r m s of efficiency, in t h e s e l e c t i o n of t h e r a p e u t i c a l t e r n a t i v e s . But t h e i r u s e in clinical p r a c t i c e de- p e n d s n o t o n l y o n t h e i r " e s s e n t i a l s i m i l a r i t y " (in t e r m s of f o r m u l a t i o n , c o m p o - sition, a n d b i o e q u i v a l e n c e as c o n s i d e r e d b y r e g u l a t o r y a g e n c i e s ) , b u t m o s t l y o n t h e c o n v i c t i o n of t h e i r i n t e r c h a n g e a b i l i t y w i t h t h e i r r e f e r e n c e c o u n t e r p a r t s . T h u s , t h e p u b l i c a t i o n of t h e c o m p a r a t i v e b i o a v a i l a b i l i t i e s of t e s t a n d r e f e r e n c e f o r m u l a t i o n s is s i g n i f i c a n t for t h e k n o w l e d g e a n d a p p r o p r i a t e a s s e s s m e n t b y t h e s c i e n t i f i c c o m m u n i t y of w h a t t h e y a r e d e a l i n g w i t h . W h e n 2 f o r m u l a t i o n s of t h e s a m e d r u g p r e s e n t s i m i l a r b i o a v a i l a b i l i t i e s t o t h e e x t e n t t h a t t h e y a r e con- s i d e r e d b i o e q u i v a l e n t b y c e r t a i n c r i t e r i a (ie, t h o s e d e s c r i b e d b y t h e C o m m i t t e e for P r o p r i e t a r y M e d i c i n a l P r o d u c t s 1 [CPMP]), it is a s s u m e d t h a t w h e n a d m i n - i s t e r e d in t h e s a m e m o l a r d o s e , t h e y will p r o v i d e t h e s a m e t h e r a p e u t i c effect, o r t h e y will b e t h e r a p e u t i c a l l y e q u i v a l e n t . 2 Enalapril m a l e a t e is t h e m o n o e t h y l e s t e r p r o d r u g of enalaprilat, an angiotensin- c o n v e r t i n g e n z y m e (ACE) inhibitor, t h a t a c t s b y d e c r e a s i n g p l a s m a a n g i o t e n s i n II a n d a l d o s t e r o n e l e v e l s , c o n s e q u e n t l y d e c r e a s i n g b l o o d p r e s s u r e (BP) b y d e c r e a s i n g p e r i p h e r a l v a s c u l a r r e s i s t a n c e . 3'4 It is i n d i c a t e d in t h e m a n a g e m e n t of all g r a d e s of e s s e n t i a l a n d r e n o v a s c u l a r h y p e r t e n s i o n , as well as in t h e t r e a t m e n t of c o n g e s t i v e h e a r t f a i l u r e a n d in a s y m p t o m a t i c p a t i e n t s w i t h left v e n t r i c u l a r d y s f u n c t i o n a n d a n e j e c t i o n f r a c t i o n of ~35%. 4 3 5
CURRENT THERAPEUTIC RESEARCH @ Enalapril h a s little p h a r m a c o l o g i c a c t i v i t y until h y d r o l y z e d in v i v o t o enala- prilat. Unlike e n a l a p r i l a t , t h e p r o d r u g is well a b s o r b e d a f t e r o r a l a d m i n i s t r a t i o n , w i t h a n o r a l a b s o r p t i o n of 55% t o 75% c o m p a r e d w i t h 3% t o 12% f o r enalapril- at. 3'4 T h e m a x i m a l p l a s m a d r u g c o n c e n t r a t i o n (Cma~) for t h e p r o d r u g is r e a c h e d w i t h i n -1 h o u r a f t e r o r a l a d m i n i s t r a t i o n , w h e r e a s C . . . . for e n a l a p r i l a t is s o m e - w h a t d e l a y e d (3-4 h o u r s a f t e r o r a l a d m i n i s t r a t i o n ) . 3'4 P l a s m a e n a l a p r i l a t con- c e n t r a t i o n s a r e r e p o r t e d l y l i n e a r l y r e l a t e d t o t h e a d m i n i s t e r e d d o s e o v e r t h e t h e r a p e u t i c r a n g e (2.5-40.0 m g ) . 3 E n a l a p r i l a t is -50% b o u n d t o p l a s m a pro- t e i n s . 3 Renal e x c r e t i o n is t h e p r i m a r y r o u t e of e l i m i n a t i o n . T h e e l i m i n a t i o n half-life (tl/2) of u n c h a n g e d e n a l a p r i l is >2 h o u r s in h e a l t h y s u b j e c t s . 3 For enala- prilat, p o l y p h a s i c e l i m i n a t i o n k i n e t i c p r o p e r t i e s h a v e b e e n r e p o r t e d , w i t h a n initial tl/2 of - 5 h o u r s a n d a r e p o r t e d t e r m i n a l half-life of 30 t o 35 h o u r s 3 or, in o t h e r c a s e s , 4 35 t o 38 h o u r s ( r a n g e , 30-87 h o u r s ) , p r o b a b l y r e f l e c t i n g its bind- ing t o t h e high-affinity, l o w - c a p a c i t y b i n d i n g s i t e of c i r c u l a t i n g s e r u m ACE. 4 S o m e e v i d e n c e s h o w s a c o r r e l a t i o n b e t w e e n p l a s m a e n a l a p r i l a t c o n c e n t r a t i o n s a n d p l a s m a ACE a c t i v i t y a n d a p o s s i b l e c o r r e l a t i o n b e t w e e n t h e s e p l a s m a con- c e n t r a t i o n s a n d d e c r e a s e s in BP. 5 A d v e r s e e f f e c t s (AEs) t h a t o c c u r w i t h e n a l a p r i l t h e r a p y u s u a l l y a r e mild a n d t r a n s i e n t , o c c u r r i n g in <10% of p a t i e n t s . 6 T h e m o s t t y p i c a l AEs a s s o c i a t e d w i t h e n a l a p r i l u s e i n c l u d e h e a d a c h e , d i z z i n e s s , fatigue, d i a r r h e a , n a u s e a a n d / o r vom- iting, r a s h , c o u g h , a n d h y p o t e n s i o n . 6 In 3% t o 6% of p a t i e n t s , t h e r a p e u t i c dis- c o n t i n u a n c e o c c u r s as a c o n s e q u e n c e of d r y , p e r s i s t e n t c o u g h , f o l l o w e d b y r a r e c a s e s (<1%) of a n g i o e d e m a , h y p o t e n s i o n , h y p e r k a l e m i a , o r a c u t e r e n a l failure. In t h e p r e s e n t s t u d y , t h e b i o e q u i v a l e n c e of 2 c o m m e r c i a l b r a n d s ( t e s t a n d r e f e r e n c e ) of e n a l a p r i l t a b l e t s (20 mg) w a s a s s e s s e d b y c o m p a r i s o n of t h e i r p h a r m a c o k i n e t i c (PK) p r o p e r t i e s t h a t d e s c r i b e t h e r a t e a n d e x t e n t o f a b s o r p t i o n - - a r e a u n d e r t h e p l a s m a c o n c e n t r a t i o n - t i m e c u r v e (AUC), C . . . . . a n d t i m e t o C . . . . . ( T m a x ) . SUBJECTS AND METHODS S t u d y D e s i g n T h i s s i n g l e - d o s e , r a n d o m i z e d , 2-way, o p e n - l a b e l , c r o s s o v e r s t u d y w a s con- d u c t e d a t t h e Clinical P h a r m a c o l o g y S t u d y Unit, H o s p i t a l Clinico San Carlos (Madrid, Spain). T h e p r o t o c o l w a s a p p r o v e d b y t h e h o s p i t a l Ethical C o m m i t t e e a n d w a s a u t h o r i z e d b y t h e S p a n i s h M i n i s t r y of Health. It w a s d e v e l o p e d ac- c o r d i n g t o t h e r e v i s e d p r i n c i p l e s of t h e D e c l a r a t i o n of Helsinki (World Medical A s s o c i a t i o n r e v i s e d S o m e r s e t West, 1996) a n d t h e Good Clinical P r a c t i c e Guide- lines ( I n t e r n a t i o n a l C o n f e r e n c e o n H a r m o n i z a t i o n , 1996). Subjects S u b j e c t s w e r e s e l e c t e d f r o m a p a n e l of h e a l t h y v o l u n t e e r s r e c r u i t e d b y t h e Clinical P h a r m a c o l o g y S t u d y Unit. I n c l u s i o n c r i t e r i a w e r e age 18 t o 40 y e a r s , b o d y w e i g h t 50 t o 100 kg, a n d b o d y m a s s i n d e x 18 t o 27 k g / m 2. All s u b j e c t s w e r e 36
A. Portol~s et aL e x a m i n e d t o v e r i f y t h e i r h e a l t h y s t a t u s ; t h e s e e x a m i n a t i o n s i n c l u d e d m e d i c a l h i s t o r y taking, vital s i g n m e a s u r e m e n t s , e l e c t r o c a r d i o g r a p h y (ECG), b l o o d s a m p l e a n a l y s i s ( b a s i c profile, c o m p l e t e b l o o d cell c o u n t , p r o t h r o m b i n time, viral s e r o l o g y ) , a n d u r i n a l y s i s ( s e d i m e n t , d r u g s , p r e g n a n c y t e s t ) . S u b j e c t s w i t h r e l e v a n t clinical, a n a l y t i c a l , o r ECG a b n o r m a l i t i e s w e r e e x c l u d e d f r o m t h e trial. A d d i t i o n a l e x c l u s i o n c r i t e r i a w e r e as follows: s m o k i n g ; h i s t o r y of a l c o h o l o r o t h e r d r u g a b u s e ; h i g h c o n s u m p t i o n (>8 c u p s / d ) of s t i m u l a t i n g b e v e r a g e s ; con- s u m p t i o n of m e d i c a t i o n t h a t c o u l d a f f e c t t h e d r u g u n d e r s t u d y (eg, a n t a c i d s , a n t i d e p r e s s a n t s ) ; r e g u l a r c o n s u m p t i o n of a n y m e d i c a t i o n in t h e 2 w e e k s b e f o r e e n r o l l m e n t ; c o n s u m p t i o n of a n y e n z y m e i n h i b i t o r s o r i n d u c e r s in t h e m o n t h b e f o r e e n r o l l m e n t ; p a r t i c i p a t i o n in a clinical trial in t h e 2 m o n t h s b e f o r e enroll- m e n t o r 4 t i m e s in t h e y e a r b e f o r e e n r o l l m e n t ; h i s t o r y of c l i n i c a l l y i m p o r t a n t illness o r m a j o r s u r g e r y in t h e 3 m o n t h s b e f o r e e n r o l l m e n t ; i n a b i l i t y t o r e l a t e t o a n d / o r c o o p e r a t e w i t h t h e i n v e s t i g a t o r s ; m e d i c a t i o n allergy; i l l n e s s e s o r disor- d e r s t h a t c o u l d a f f e c t t h e a b s o r p t i o n , d i s t r i b u t i o n , m e t a b o l i s m , a n d / o r excre- t i o n of d r u g s (eg, m a l a b s o r p t i o n , e d e m a s , r e n a l a n d / o r h e p a t i c failure); a his- t o r y of p o s i t i v e s e r o l o g y f o r h e p a t i t i s B o r C ( n o t d u e t o i m m u n i z a t i o n ) o r HIV; b l o o d l o s s o r d o n a t i o n >200 mL in t h e 3 m o n t h s b e f o r e e n r o l l m e n t ; b l o o d o r b l o o d - d e r i v a t i v e t r a n s f u s i o n in t h e 6 m o n t h s b e f o r e e n r o l l m e n t ; a n d e x h a u s t i n g p h y s i c a l e x e r c i s e in t h e 72 h o u r s b e f o r e e n r o l l m e n t . P r e g n a n t , p o s s i b l y preg- n a n t , o r b r e a s t f e e d i n g w o m e n w e r e e x c l u d e d f r o m t h e s t u d y . W o m e n of child- b e a r i n g a g e w e r e r e q u i r e d t o u s e a n e f f e c t i v e m e t h o d of b i r t h c o n t r o l ( e x c e p t o r a l a n o v u l a t o r y d r u g s ) t h r o u g h o u t t h e s t u d y . All eligible s u b j e c t s p r o v i d e d w r i t t e n i n f o r m e d c o n s e n t t o p a r t i c i p a t e . M e t h o d s S u b j e c t s w e r e a d m i t t e d t o t h e s t u d y u n i t at - 8 PM o n e a c h of t h e 2 e v e n i n g s b e f o r e s t u d y d r u g a d m i n i s t r a t i o n . Clinical e n t r y c o n t r o l s ( p h y s i c a l e x a m i n a t i o n a n d s u b j e c t i n t e r v i e w ) w e r e p e r f o r m e d , a n d all s u b j e c t s r e c e i v e d a s t a n d a r d d i n n e r ( b a l a n c e d c o m p o s i t i o n w i t h -25% of d a i l y c a l o r i e s ) . S u b j e c t s f a s t e d for at l e a s t 10 h o u r s b e f o r e a n d 4 h o u r s a f t e r s t u d y d r u g a d m i n i s t r a t i o n . S u b j e c t s w e r e r a n d o m i z e d , a c c o r d i n g t o a c o m p u t e r - g e n e r a t e d r a n d o m i z a - t i o n t a b l e of s e q u e n c e s , t o r e c e i v e e i t h e r t h e t e s t * o r r e f e r e n c e ~ f o r m u l a t i o n of e n a l a p r i l (20-mg t a b l e t ) a t s t u d y p e r i o d 1 a n d t h e o p p o s i t e f o r m u l a t i o n a t s t u d y p e r i o d 2. S t u d y p e r i o d s w e r e s e p a r a t e d b y a w a s h o u t p e r i o d of a t l e a s t 7 d a y s . Drug a d m i n i s t r a t i o n s t a r t e d a t 8 AM, a n d v o l u n t e e r s r e c e i v e d t h e m e d i c a t i o n w i t h 150 mL of w a t e r at r o o m t e m p e r a t u r e b y a n u r s e . D r u g Analysis Blood s a m p l e s of - 1 0 mL e a c h w e r e d r a w n b y a n u r s e a t 15 t i m e p o i n t s : b a s e l i n e ( i m m e d i a t e l y b e f o r e s t u d y d r u g a d m i n i s t r a t i o n ) ; 30, 45, 60, 75, 105, 135, 180, *Trademark: Enalapril Farmoz ® (Tecnimede Sociedade T~cnico-Medicinal S.A., Prior Velho, Portugal). tTrademark: Renitec ® (Merck Sharp & Dohme, Lda., Pa(~o de Arcos, Portugal). 37
CURRENT THERAPEUTIC RESEARCH ® 195, a n d 225 m i n u t e s ; a n d 5, 8, 12, 24, a n d 36 h o u r s a f t e r s t u d y d r u g a d m i n i s - t r a t i o n . S a m p l e s w e r e c e n t r i f u g e d at 3000 r p m for 10 m i n u t e s ( a t 4°C), a n d t h e o b t a i n e d p l a s m a s a m p l e s w e r e s e p a r a t e d in t w o 1.5-mL a l i q u o t s a n d s t o r e d in s u i t a b l y l a b e l e d , t i g h t l y s e a l e d t u b e s at -30°C. After 24 h o u r s , t h e s a m p l e s w e r e t r a n s f e r r e d t o -80°C. V o l u n t e e r s r e m a i n e d u n d e r m e d i c a l s u p e r v i s i o n a t t h e s t u d y c e n t e r u n t i l 12 h o u r s a f t e r s t u d y d r u g a d m i n i s t r a t i o n , a n d r e t u r n e d at 24 a n d 36 h o u r s a f t e r a d m i n i s t r a t i o n for t h e l a s t e x t r a c t i o n s . A n a l y t i c a l d e t e r m i n a t i o n of p l a s m a d r u g a n d m e t a b o l i t e c o n c e n t r a t i o n s w e r e p e r f o r m e d b y MCC AnaHtica S.A. ( B a r c e l o n a , Spain) a n d f o l l o w e d a n a c i d s o l i d - liquid e x t r a c t i o n w i t h a r e v e r s e d - p h a s e h i g h - p r e s s u r e liquid c h r o m a t o g r a p h y s e p a r a t i o n a n d m a s s s p e c t r o m e t r y d e t e c t o r . Lisinopril w a s u s e d as a n i n t e r n a l s t a n d a r d . T h e m e t h o d of a n a l y s i s w a s v a l i d a t e d u n d e r t h e p r i n c i p l e s of Good L a b o r a t o r y P r a c t i c e t h r o u g h t h e f o l l o w i n g p a r a m e t e r s : l i n e a r i t y , p r e c i s i o n , i n t r a - a s s a y a n d i n t e r a s s a y a c c u r a c y , limit of q u a n t i f i c a t i o n (LOQ), v a l i d a t i o n of t h e d i l u t i o n f a c t o r , s p e c i f i c i t y , s t a b i l i t y , a n d r e c o v e r y . T h e a n a l y t i c a l p a r t of t h e s t u d y w a s d e v e l o p e d b l i n d l y . Pharmacokinetic Analysis PK p r o p e r t i e s w e r e c a l c u l a t e d b y a n o n c o m p a r t m e n t a l a p p r o a c h f r o m p l a s m a c o n c e n t r a t i o n s of e n a l a p r i l a n d e n a l a p r i l a t , u s i n g WinNonlin P r o s o f t w a r e ver- s i o n 2.1 ( P h a r s i g h t C o r p o r a t i o n , M o u n t a i n View, California). C . . . . w a s e s t i m a t e d d i r e c t l y f r o m o b s e r v e d c o n c e n t r a t i o n s , a n d T ..... as t h e c o r r e s p o n d i n g t i m e p o i n t at w h i c h C ..... o c c u r r e d . AUCt w a s c a l c u l a t e d b y t h e l i n e a r t r a p e z o i d a l m e t h o d until t h e l a s t m e a s u r a b l e p l a s m a d r u g c o n c e n t r a t i o n , a n d AUC f r o m t i m e 0 t o i n f i n i t y (AUC0_~) w a s c a l c u l a t e d as: AUC0_~ = AUC t + Ct/K e, w h e r e Ct is t h e p l a s m a d r u g c o n c e n t r a t i o n a t t i m e t a n d Ke is t h e e l i m i n a t i o n r a t e c o n s t a n t . T h e m e a n r e s i d e n c e t i m e (MRT0_~) a n d tl/2 a l s o w e r e c a l c u l a t e d a n d p r e s e n t e d for d e s c r i p t i v e p u r p o s e s . Given t h e i n a c t i v e n a t u r e of enalapril, t h e PK p r o p e r t i e s of e n a l a p r i l a t w e r e d e f i n e d as p r i m a r y a s s e s s m e n t c r i t e r i a . AUC is c o n s i d e r e d t h e m o s t r e p r e s e n t a t i v e p a r a m e t e r of b i o e q u i v a l e n c e . Tolerability Assessment For t o l e r a b i l i t y a s s e s s m e n t , clinical c o n t r o l s (vital c o n s t a n t s , eg, BP, t e m p e r a - t u r e , o r h e a r t r a t e , a n d t h e q u e s t i o n o n AE) w e r e p e r f o r m e d a t 5, 12, 24, a n d 36 h o u r s a f t e r s t u d y d r u g a d m i n i s t r a t i o n . L a b o r a t o r y a n a l y s e s a n d ECG a l s o w e r e p e r f o r m e d a t p r e s t u d y a n d p o s t s t u d y t i m e s . T o l e r a b i l i t y of t h e 2 f o r m u - l a t i o n s w a s t h e s e c o n d a r y a s s e s s m e n t c r i t e r i o n ; t h u s , o n l y d e s c r i p t i v e s t a t i s - t i c s w e r e f o r e s e e n a n d p e r f o r m e d . Statistical Analysis T h e s a m p l e s i z e n e e d e d f o r >90% p o w e r w a s d e t e r m i n e d u s i n g PC-SIZE s o f t w a r e v e r s i o n 1.0 ( S t a t T o o l s TM, P a l i s a d e C o r p o r a t i o n , Newfield, New York) a n d vari- a b i l i t y d a t a f r o m a p r e v i o u s l y p u b l i s h e d s t u d y . 7 38
A. Portol(~s et aL C o n c e n t r a t i o n - d e r i v e d p a r a m e t e r s w e r e a n a l y z e d (WinNonlin, P h a r s i g h t Cor- p o r a t i o n , M o u n t a i n View, California) u s i n g a p a r a m e t r i c m e t h o d , c o n d u c t e d b y m e a n s of a n a l y s i s of v a r i a n c e (ANOVA), u s i n g as d e p e n d e n t v a r i a b l e s t h e loga- r i t h m i c t r a n s f o r m a t i o n s (Ln) of t h e t e s t / r e f e r e n c e r a t i o s of t h e p a r a m e t e r s AUC0_~, AUC t, C . . . . . a n d Cmax/AUC0_~. In t h e a n a l y s i s , t h e following m o d e l ef- f e c t s w e r e c o n s i d e r e d : form, p e r i o d , s e q u e n c e , a n d v o l u n t e e r ( s e q u e n c e ) . T h e 90% CIs w e r e c a l c u l a t e d for t h e s e r a t i o s a n d u s e d as b i o e q u i v a l e n c e - a s s e s s m e n t c r i t e r i a . A c c e p t a n c e c r i t e r i a f o r t h e 90% CIs w e r e p r o s p e c t i v e l y d e f i n e d in t h e s t u d y p r o t o c o l as 80% t o 125% f o r Ln AUC r a t i o s a n d 70% t o 143% for Ln C . . . . r a t i o s . T h e T . . . . . s f r o m b o t h f o r m u l a t i o n s w e r e c o m p a r e d u s i n g a n o n p a r a m e t - ric m e t h o d (CI of t h e m e d i a n of t h e d i f f e r e n c e s b y t h e W i l c o x o n s i g n e d r a n k t e s t ) , a n d t h e a c c e p t a n c e c r i t e r i o n f o r t h i s p a r a m e t e r w a s 70% t o 130%. RESULTS Subjects T w e n t y - f o u r w h i t e h e a l t h y v o l u n t e e r s w e r e i n c l u d e d in t h e s t u d y (12 m e n , 12 w o m e n ; m e a n [SD] age, 22.8 [2.2] y e a r s [range, 19-30 y e a r s ] ; m e a n [SD] b o d y w e i g h t , 65.1 [12.4] kg [men, 75.3 (9.1) kg; w o m e n , 54.9 (4.6) kg]; m e a n [SD] h e i g h t , 173.0 [10.2] c m [men, 182.7 (4.6) cm; w o m e n , 163.9 (3.6) c m ] ) . One s u b j e c t (4.2%) w i t h d r e w b e t w e e n s t u d y p e r i o d s f o r p e r s o n a l r e a s o n s . T h e re- s u i t s of 23 s u b j e c t s w e r e i n c l u d e d in t h e PK a n a l y s i s . Analytical Assay A s s e s s m e n t of PK p a r a m e t e r s d e t e r m i n e d t h e a d e q u a c y of t h e a n a l y t i c a l m e t h o d f o r t h e d e t e r m i n a t i o n of p l a s m a d r u g a n d m e t a b o l i t e c o n c e n t r a t i o n s . T h e LOQ w a s s e t at 1 n g / m L f o r b o t h e n a l a p r i l a n d e n a l a p r i l a t . M e a n p l a s m a d r u g c o n c e n t r a t i o n s of e n a l a p r i l a n d e n a l a p r i l a t f o r b o t h t h e t e s t a n d r e f e r e n c e f o r m u l a t i o n s a r e p r e s e n t e d in F i g u r e 1. No p r e d o s e d e t e c t - a b l e levels w e r e f o u n d in a n y of t h e s u b j e c t s in e i t h e r t r e a t m e n t p e r i o d . P h a r m a c o k i n e t i c Analysis T h e PK p r o p e r t i e s of e n a l a p r i l a n d e n a l a p r i l a t a r e s u m m a r i z e d in T a b l e I a n d T a b l e II. M e a n (SD) C ..... s of 118.58 (52.38) n g / m L a n d 134.63 (56.28) n g / m L ( e n a l a p r i l ) a n d 70.02 (31.90) n g / m L a n d 73.60 (30.31) n g / m L ( e n a l a p r i l a t ) for t e s t o r r e f e r e n c e f o r m u l a t i o n s , r e s p e c t i v e l y , w e r e a t t a i n e d a t m e d i a n T ..... s of 0.96 a n d 0.90 h o u r s ( e n a l a p r i l ) a n d 3.25 a n d 3.39 h o u r s ( e n a l a p r i l a t ) ( r e s p e c - tively, f o r t e s t a n d r e f e r e n c e f o r m u l a t i o n s ) . R e s u l t s of MRT0_~ a n d tl/2 a r e s h o w n in T a b l e s I a n d II. All s u b j e c t s (100.0%) p r e s e n t e d a n AUCt/AUC0_~ r a t i o >80%, a n d t h e ANOVA of Ln C . . . . . AUC t, a n d AUC0_~ s h o w e d n o s t a t i s t i - c a l l y s i g n i f i c a n t s e q u e n c e o r p e r i o d effect. T h e o b t a i n e d 90% CIs for t h e pa- r a m e t e r r a t i o s a r e p r e s e n t e d in T a b l e III. T h e r a t i o s a n d t h e i r 90% CIs c a l c u l a t e d for t h e L n - t r a n s f o r m e d p a r a m e t e r s for e n a l a p r i l w e r e Ln C . . . . . 88.90% (77.35%-102.16%); Ln AUCt, 94.08% (87.14%- 39
CURRENT THERAPEUTIC RESEARCH ® 1 4 0 - ,007 A , . I e I o - ; 17 ~ k - EnalapriI-R --o- EnalapriI-T - O - Enalaprilat-R Enalaprilat-T 2'4 36 T i m e A f t e r S t u d y D r u g A d m i n i s t r a t i o n ( h ) Figure 1. Plasma d r u g concentrations of the test (T; trademark: Enalapril Farmoz ®, Tec- nimede Sociedade T~cnico-Medicinal S.A., Prior Velho, Portugal) and reference (R; trade- mark: Renitec ®, Merck Sharp & Dohme, Lda., Pa(~o de Arcos, Portugal) formulations of enalapril ( p r o d r u g ) and enalaprilat (active metabolite) (N = 23 subjects). 101.58%); a n d Ln AUC0_~, 94.19% (87.42%-101.49%). T h e r e s p e c t i v e v a l u e s f o r e n a l a p r i l a t w e r e 92.98% (83.56%-103.46%) f o r Ln C . . . . . 95.87% (88.60%-103.74%) f o r Ln AUCt, a n d 96.27% (89.20%-103.91%) for Ln AUC0_~. All of t h e c a l c u l a t e d i n t e r v a l s w e r e w i t h i n t h e p r e d e f i n e d b i o e q u i v a l e n c e r a n g e s ; also, 90% CIs ob- t a i n e d f o r t h e m e d i a n of d i f f e r e n c e s of T . . . . w e r e w i t h i n p r e d e f i n e d r a n g e s f o r b o t h e n a l a p r i l (86.14%-113.86%) a n d e n a l a p r i l a t (88.90%-100.00%). T o l e r a b i l i t y All 24 s u b j e c t s w e r e i n c l u d e d in t h e t o l e r a b i l i t y a s s e s s m e n t . During t h e c o u r s e of t h e s t u d y , 7 AEs w e r e r e p o r t e d . Five p o s s i b l y t r e a t m e n t - r e l a t e d AEs w e r e r e c o r d e d ( d i z z i n e s s , 2 s u b j e c t s [8.3%]; fatigue, h e a d a c h e , a n d s o m n o l e n c e , 1 s u b j e c t e a c h [4.2%]). One s u b j e c t (4.2%) e x p e r i e n c e d an AE w i t h d o u b t f u l treat- m e n t r e l a t i o n s h i p ( d i a r r h e a ) , a n d 1 s u b j e c t (4.2%) e x p e r i e n c e d a n AE t h a t w a s n o t t r e a t m e n t r e l a t e d ( d i z z i n e s s ) . All AEs w e r e mild e x c e p t 1 c a s e of d i z z i n e s s , w h i c h w a s m o d e r a t e . All AEs r e s o l v e d c o m p l e t e l y a n d s p o n t a n e o u s l y . Six AEs o c c u r r e d d u r i n g a d m i n i s t r a t i o n of t h e r e f e r e n c e f o r m u l a t i o n , a n d 1 o c c u r r e d d u r i n g a d m i n i s t r a t i o n of t h e t e s t f o r m u l a t i o n . No s a f e t y c o n c e r n s a r o s e . 40
T a b l e I. P h a r m a c o k i n e t i c p r o p e r t i e s o f enalapril ( p r o d r u g ) f r o m t h e test* and reference ~ (Ref) f o r m u l a t i o n s (N = 23 subjects). AUCt, n g / m L , h AUCo_~ , n g / m L , h Parameter Test Ref Test Ref Test Ref Test Ref Test Ref Test Ref C . . . . n g / m L T . . . . h MRTo_~ , h t l / 2 , h M e a n 1 1 8 . 5 8 1 3 4 . 6 3 0 . 9 6 0 . 9 0 1 8 9 . 4 0 2 0 0 . 6 5 1 9 2 . 0 7 2 0 3 . 6 2 1.67 1.61 0 . 8 7 0.82 SD 5 2 . 3 8 5 6 . 2 8 0 . 3 4 0 . 2 6 8 5 . 5 2 7 9 . 9 8 8 5 . 5 0 8 1 . 0 2 0.33 0 . 3 4 0.33 0.22 M i n i m u m 4 8 . 2 8 4 8 . 4 3 0 . 5 0 0 . 5 0 1 0 2 . 6 7 9 0 . 7 0 1 0 4 . 5 3 9 1 . 9 2 1.23 1.07 0.59 0 . 5 4 M e d i a n 1 0 8 . 9 5 132.51 1.00 0.75 1 7 1 . 4 8 198.81 1 7 5 . 0 8 2 0 1 . 5 8 1.61 1.60 0.79 0 . 7 4 M a x i m u m 2 9 1 . 9 4 2 5 1 . 5 4 2.25 1.75 4 8 3 . 8 6 3 9 0 . 7 7 487.01 3 9 5 . 0 7 2 . 6 0 2.85 1.76 1.37 CV% 4 4 . 1 7 41.81 35.81 2 8 . 6 3 4 5 . 1 5 3 9 . 8 6 44.51 3 9 . 7 9 19.71 2 1 . 2 7 3 7 . 4 7 2 6 . 3 7 G e o m e t r i c mean 1 0 9 . 6 7 1 2 2 . 9 8 0.91 0 . 8 7 1 7 5 . 3 7 1 8 5 . 8 7 1 7 8 . 1 8 1 8 8 . 6 8 1.64 1.58 0.83 0 . 8 0 H a r m o n i c mean 1 0 1 . 9 7 1 1 1 . 3 7 0 . 8 7 0.85 1 6 4 . 4 5 1 7 1 . 8 9 1 6 7 . 2 9 1 7 4 . 5 4 1.61 1.56 0.79 0 . 7 8 C m a x = maximum plasma drug concentration; Tma x = time to maximal plasma drug concentration; AUC t = area under the plasma concentration-time curve to the last measurable concentration; AUC o ~ = area under the plasma concentration-time curve from time 0 to infinity; MRT o ~ = mean residence time; tl/2 = elimination half-life; CV% = coefficient of variation. *Trademark: Enalapril Farmoz ® (Tecnimede Sociedade T~cnico-Medicinal S.A., Prior Velho, Portugal). tTrademark: Renitec ® (Merck Sharp & Dohme, Lda., Pa(~o de Arcos, Portugal).
NI -q -q T a b l e II. P h a r m a c o k i n e t i c p r o p e r t i e s o f e n a l a p r i l a t (active m e t a b o l i t e ) f r o m t h e test* and reference t (Ref) f o r m u l a t i o n s o f e n a l a p r i l ( p r o d r u g ) (N = 23 subjects). C . . . . n g / m L T . . . . h AUCt, n g / m L , h AUCo_~ , n g / m L , h MRTo_~ , h t l / 2 , h Parameter Test Ref Test Ref Test Ref Test Ref Test Ref Test Ref M e a n 7 0 . 0 2 7 3 . 6 0 3.25 3.39 5 6 3 . 4 8 5 8 8 . 6 9 5 8 7 . 1 0 61 0.07 9 . 6 4 9 . 3 7 6 . 0 6 5 . 9 8 SD 3 1 . 9 0 30.31 0.71 0.82 2 2 6 . 5 0 2 3 4 . 0 0 2 3 7 . 9 5 2 4 1 . 3 8 3.1 0 2.91 2 . 0 4 2.01 M i n i m u m 2 1 . 4 2 1 7.89 2.25 1.75 233.41 2 5 2 . 2 8 2 4 9 . 2 3 269.81 4.91 4 . 2 8 2 . 5 4 2.1 3 M e d i a n 7 3 . 9 9 6 9 . 6 2 3.00 3.25 4 8 3 . 3 4 5 2 9 . 6 5 5 2 3 . 0 9 5 4 9 . 8 7 9.1 6 9 . 2 7 5.52 6.01 M a x i m u m 1 5 2 . 5 7 1 3 6 . 8 8 5.00 5.00 1 0 5 6 . 2 2 1 0 8 9 . 0 9 1 0 9 9 . 6 5 1 1 5 5 . 5 8 1 6 . 1 2 1 5 . 9 0 9.93 9.81 CV% 4 5 . 5 6 4 1 . 1 8 2 1 . 8 8 2 4 . 2 3 4 0 . 2 0 3 9 . 7 5 4 0 . 5 3 3 9 . 5 7 3 2 . 1 4 3 1 . 0 8 3 3 . 6 5 3 3 . 6 9 G e o m e t r i c mean 62.51 6 7 . 0 3 3.18 3.30 5 2 4 . 1 9 5 4 5 . 6 0 5 4 6 . 4 4 566.51 9.1 7 8.93 5 . 7 0 5 . 6 0 H a r m o n i c mean 5 4 . 5 7 59.41 3.12 3.20 4 8 8 . 9 4 5 0 4 . 5 2 51 0.84 5 2 5 . 6 3 8 . 7 0 8 . 4 6 5.33 5.1 6 C m a x = maximum plasma drug concentration; Tma x = time to maximal plasma drug concentration; AUC t = area under the plasma concentration-time curve to the last measurable concentration; AUC o ~ = area under the plasma concentration-time curve from time 0 to infinity; MRT o ~ = mean residence time; tl/2 = elimination half-life; CV% = coefficient of variation. *Trademark: Enalapril Farmoz ® (Tecnimede Sociedade T~cnico-Medicinal S.A., Prior Velho, Portugal). tTrademark: Renitec ® (Merck Sharp & Dohme, Lda., Pa(~o de Arcos, Portugal).
A. Portol~s et aL T a b l e III. Differences in p h a r m a c o k i n e t i c properties o f enalapril ( p r o d r u g ) and e n a l a p r i l a t (active m e t a b o l i t e ) b e t w e e n t h e test* and reference t f o r m u l a t i o n s (N = 23 subjects). Property Enalapril Enalaprilat Ln Cma x Difference, mean (SE) - 0 . 1 2 (0.08) - 0 . 0 7 ( 0 . 0 6 ) Ratio, % 8 8 . 9 0 9 2 . 9 8 9 0 % CI, % 7 7 . 3 5 t o 1 0 2 . 1 6 8 3 . 5 6 t o 1 0 3 . 4 6 Ln AUC t Difference, mean (SE) - 0 . 0 6 (0.04) - 0 . 0 4 ( 0 . 0 5 ) Ratio, % 9 4 . 0 8 9 5 . 8 7 9 0 % CI, % 8 7 . 1 4 t o 1 0 1 . 5 8 8 8 . 6 0 t o 1 0 3 . 7 4 Ln AUCo_~ Difference, mean (SE) - 0 . 0 6 (0.04) - 0 . 0 4 ( 0 . 0 4 ) Ratio, % 9 4 . 1 9 9 6 . 2 7 9 0 % CI, % 8 7 . 4 2 t o 1 0 1 . 4 9 8 9 . 2 0 t o 103.91 T m a x :~ Differences, m e d i a n , h 0.0 - 0 . 1 2 5 9 0 % CI, difference, h - d e c i m a l - 0 . 1 2 5 t o 0 . 1 2 5 - 0 . 3 7 5 t o 0 . 0 9 0 % CI, difference, % ( w i t h respect t o mean o f reference f o r m ) 8 6 . 1 4 t o 1 1 3 . 8 6 8 8 . 9 0 t o 1 0 0 . 0 0 Ln = logarithmically (e-base) transformed; C m a x = maximal plasma drug concentration; AUC t = area under the plasma concentration-time curve to the last measurable concentration; AUCo~ = area under the plasma concentration-time curve from time 0 to infinity; Tma x -- time to maximal plasma drug concentration. *Trademark: Enalapril Farmoz ® (Tecnimede Sociedade T~cnico-Medicinal S.A., Prior Velho, Portugal). tTrademark: Renitec ® (Merck Sharp & Dohme, Lda., Pa(~o de Arcos, Portugal). SNo significant differences were found between the test and reference formulations. L a b o r a t o r y a n a l y s i s f o r t o l e r a b i l i t y r e v e a l e d s o m e m o d i f i c a t i o n s in t h e bio- c h e m i c a l a n d h e m a t o l o g i c r e s u l t s , n a m e l y : (1) d e c r e a s e d r e d b l o o d ceil c o u n t (9 s u b j e c t s [37.5%]), (2) s l i g h t e l e v a t i o n s in a b i o c h e m i c a l p a r a m e t e r ( t o t a l bilirubin, 2 s u b j e c t s [8.3%]), (3) r e d u c t i o n s in o t h e r b i o c h e m i c a l p a r a m e t e r s (alkaline p h o s p h a t a s e , 1 s u b j e c t [4.2%]; u r i c acid, 4 [16.7%]; a n d t o t a l c h o l e s - t e r o l , 3 [12.5%]), a n d (4) p r e s e n c e of u r i n e s e d i m e n t a n o m a l i e s ( o x a l a t e s , 2 s u b j e c t s [8.3%]; a n d w h i t e b l o o d ceils, 1 [4.2%]). S y m p t o m s w e r e n o t d e t e c t e d in a n y of t h e s e c a s e s , a n d all of t h e s e l a b o r a t o r y a b n o r m a l i t i e s w e r e c o n s i d e r e d c l i n i c a l l y n o n s i g n i f i c a n t . T h e m e a n v a l u e s o b t a i n e d f o r s y s t o l i c a n d d i a s t o l i c BP a r e p r e s e n t e d in F i g u r e 2. After 5 h o u r s , t h e m e a n v a l u e s o b t a i n e d for b o t h f o r m u l a t i o n s w e r e s i g n i f i c a n t l y l o w e r t h a n b a s e l i n e v a l u e s ( b o t h P < 0.05), c o r r e s p o n d i n g t o a m i n i m u m in t h e s y s t o l i c a n d d i a s t o l i c BPs, w i t h m e a n (SD) s y s t o l i c BP v a l u e s of 102 (18) m m Hg for t h e r e f e r e n c e f o r m u l a t i o n a n d of 101 (11) m m Hg for t h e t e s t f o r m u l a t i o n . 43
CURRENT THERAPEUTIC RESEARCH ® - ! - SBP-T - 0 - SBP-R DBP-T - ~ - DBP-R 1 4 0 L a. 6 0 .: . . . . . . . . . . 4 O 2 o ";" l'z 14 T i m e A f t e r S t u d y D r u g A d m i n i s t r a t i o n ( h ) Figure 2. Systolic and diastolic blood pressures (SBP and DBP, respectively) of the test (T; trademark: Enalapril Farmoz ®, Tecnimede Sociedade T~cnico-Medicinal S.A., Prior Velho, Portugal) and reference (R; trademark: Renitec ®, Merck Sharp & Dohme, Lda., Pa(~o de Arcos, Portugal) formulations of enalapril (N = 23 subjects). *P < 0.05 5 hours versus baseline. D I S C U S S I O N B o t h t h e t e s t a n d r e f e r e n c e f o r m u l a t i o n s of e n a l a p r i l e x h i b i t e d o v e r l a p p i n g p l a s m a p r o f i l e s . T h e f a c t t h a t n o m o d e l e f f e c t s ( p e r i o d o r s e q u e n c e ) o r d e t e c t - a b l e p r e d o s e p l a s m a d r u g c o n c e n t r a t i o n s w e r e f o u n d i n d i c a t e s t h e a d e q u a c y of t h e p r o p o s e d s t u d y d e s i g n a n d of t h e s t u d y c o n d u c t i o n . T o e n s u r e a r e l i a b l e e s t i m a t e of t h e e x t e n t of a b s o r p t i o n , a c o l l e c t i o n p e r i o d of a t l e a s t 3 tl/2S is r e c o m m e n d e d b y US F o o d a n d Drug A d m i n i s t r a t i o n 8 a n d CPMP 1 g u i d e l i n e s . T h i s r e q u i s i t e w a s fulfilled, a n d t h e m e a n e x t r a p o l a t e d a r e a w a s well b e l o w 20% f o r b o t h f o r m u l a t i o n s , i n d i c a t i n g t h a t t h e e x t r a c t i o n p e r i o d w a s a d e q u a t e t o fully c h a r a c t e r i z e t h e PK p r o p e r t i e s of t h e p r o d r u g a n d its a c t i v e m e t a b o l i t e . T a k i n g i n t o a c c o u n t t h e PK c h a r a c t e r i s t i c s of t h e p r o d r u g a n d of its a c t i v e m e t a b o l i t e , a s i n g l e - d o s e PK s t u d y w a s d e e m e d as a p p r o p r i a t e . T h e c h o s e n d o s e fails w i t h i n t h e r a n g e of c l i n i c a l l y a d m i n i s t e r e d d o s e s . T h e s t u d y w a s c o n d u c t e d u n d e r f a s t i n g c o n d i t i o n s t o r e d u c e t h e p o s s i b l e i n t e r f e r e n c e of f o o d o v e r a b s o r p t i o n k i n e t i c s . 44
A. Portol~s et aL B e c a u s e t h e a s s e s s e d v a r i a b l e s w e r e PK p r o p e r t i e s , it w a s r e g a r d e d u n n e c - e s s a r y t o u s e a b l i n d e d d e s i g n . N e v e r t h e l e s s , as m e n t i o n e d e a r l i e r , t h e a n a l y t i - cal p a r t of t h e s t u d y w a s c o n d u c t e d b l i n d l y . T h e d e s i g n w e c h o s e c o m p l i e s w i t h E u r o p e a n 1 a n d US 8 g u i d e l i n e s o n b i o a v a i l a b i l i t y / b i o e q u i v a l e n c e s t u d i e s . T h e s t u d y d e s i g n is s u i t e d t o its o b j e c - t i v e s , a n d t h e s t u d y w a s c a r r i e d o u t w i t h n o s i g n i f i c a n t d e v i a t i o n s f r o m t h e p r o t o c o l . T h e c a l c u l a t e d PK p a r a m e t e r s a r e s i m i l a r t o t h o s e p r e v i o u s l y d e s c r i b e d : T . . . . f o r e n a l a p r i l a n d e n a l a p r i l a t w e r e in a c c o r d a n c e w i t h p r e v i o u s l y r e p o r t e d v a l u e s . 3 In o u r s t u d y , t h e tu2 f o r e n a l a p r i l w a s r e l a t i v e l y s h o r t f o r b o t h f o r m u - l a t i o n s ( m e d i a n s : t e s t , 0.79 h o u r ; r e f e r e n c e , 0.74 h o u r ) ; f o r e n a l a p r i l a t , t h e m e - d i a n tl/2s w e r e 5.52 a n d 6.01 h o u r s f o r t h e t e s t a n d r e f e r e n c e f o r m u l a t i o n s , r e s p e c t i v e l y . A l t h o u g h p o l y p h a s i c e l i m i n a t i o n k i n e t i c p r o p e r t i e s h a v e b e e n de- s c r i b e d f o r e n a l a p r i l , w i t h m e a n t e r m i n a l half-lives - 3 0 h o u r s , s i m i l a r half- l i v e s f o r e n a l a p r i l a t h a v e b e e n r e p o r t e d in a s e p a r a t e b i o e q u i v a l e n c e s t u d y b y R i b e i r o e t al.7 T h i s d i f f e r e n c e in t h e e s t i m a t e d half-lives is p r o b a b l y r e l a t e d t o t h e s a m p l i n g p e r i o d ( i n o u r c a s e , u p t o 36 h o u r s a f t e r s t u d y d r u g a d m i n i s t r a t i o n , a n d in t h e s t u d y b y R i b e i r o e t al, 7 u p t o 24 h o u r s a f t e r a d m i n i s t r a t i o n ) . A l t h o u g h t h e CPMP g u i d e l i n e s ~ r e c o m m e n d t h a t b i o e q u i v a l e n c e s h o u l d b e a s s e s s e d b y c o m p a r i n g t h e b i o a v a i l a b i l i t y o f t h e p a r e n t c o m p o u n d a d m i n i s - t e r e d , in t h i s c a s e , g i v e n t h a t t h e p a r e n t c o m p o u n d is i n a c t i v e a n d its m e t a b o - lite is in f a c t t h e c o m p o u n d e x h i b i t i n g p h a r m a c o l o g i c a c t i v i t y , it w a s c o n s i d - e r e d a p p r o p r i a t e t o c o m p a r e t h e b i o a v a i l a b i l i t y o f t h e m e t a b o l i t e in b o t h f o r m u l a t i o n s . All 90% CIs o b t a i n e d f o r e n a l a p r i l ( t h e p r o d r u g ) a n d e n a l a p r i l a t ( t h e a c t i v e m e t a b o l i t e ) w e r e w i t h i n t h e p r e d e f i n e d r a n g e s o f b i o e q u i v a l e n c e a c c e p t a n c e ; t h u s , t h e 2 f o r m u l a t i o n s a r e c o n s i d e r e d b i o e q u i v a l e n t . A l t h o u g h a r e l a t i v e l y h i g h v a r i a b i l i t y w a s f o u n d f o r s o m e p a r a m e t e r s o f e a c h f o r m u l a t i o n , t h a t w a s n o t t h e c a s e in t h e c o m p a r i s o n of t h e i n t r a s u b j e c t d i f f e r e n c e s a n d r a t i o s . In g e n e r a l , e n a l a p r i l w a s well t o l e r a t e d . No u n e x p e c t e d AEs o c c u r r e d , a n d t h e r e p o r t e d p o s s i b l y t r e a t m e n t - r e l a t e d AEs c o u l d b e e x p l a i n e d b y t h e h y p o - t e n s i v e e f f e c t of t h e d r u g . T h e h e m a t o l o g i c c h a n g e s in t h e r e d b l o o d cell c o u n t w e r e a t t r i b u t a b l e t o t h e b l o o d e x t r a c t i o n d u r i n g t h e s t u d y . No p r o b l e m s c o n - c e r n i n g s a f e t y of t h e f o r m u l a t i o n w e r e d e t e c t e d . R e s u l t s f o r BP w e r e c o l l e c t e d t o a s s e s s t h e t o l e r a b i l i t y of t h e f o r m u l a t i o n s a n d n o t t h e i r p h a r m a c o d y n a m i c p r o p e r t i e s . A c c o r d i n g l y , t h e a s s e s s m e n t t i m e s a n d t h e s t u d y d e s i g n d i d n o t allow f o r a c l o s e r m o n i t o r i n g o f t h e BP as w o u l d b e n e c e s s a r y f o r a p h a r m a c o d y n a m i c a s s e s s m e n t . H o w e v e r , u n l i k e w h a t w a s r e p o r t e d b y R i b e i r o e t al7 o n t h e a b s e n c e of a n e v a l u a b l e e f f e c t (BP) of e n a l a p r i l in h e a l t h y v o l u n t e e r s , w e f o u n d s i g n i f i c a n t r e d u c t i o n s in m e a n BPs ( P < 0.05), w h i c h r e t u r n e d t o b a s e l i n e v a l u e s a t t h e f o l l o w i n g m e a s u r e m e n t ( a s s e s s e d a t 12 h o u r s a f t e r s t u d y d r u g a d m i n i s t r a t i o n ) . T h i s f i n d i n g is in a c c o r d a n c e w i t h t h e r e p o r t e d r e d u c t i o n in BP f o u n d in a n o t h e r s t u d y 4 in n o r m o t e n s i v e i n d i v i d u - 45
CURRENT THERAPEUTIC RESEARCH @ a l s , a n d s u g g e s t s t h a t , f o r t h i s g r o u p o f d r u g s ( H y p o t e n s i v e s ) , a m o r e d e t a i l e d a s s e s s m e n t o f p h a r m a c o d y n a m i c p r o p e r t i e s c o u l d b e p e r f o r m e d in h e a l t h y s u b j e c t s u s i n g a m o r e s p e c i f i c s t u d y d e s i g n (ie, B P m o n i t o r i n g ) . C O N C L U S I O N S I n t h i s s t u d y o f 2 c o m m e r c i a l b r a n d s ( t e s t a n d r e f e r e n c e f o r m u l a t i o n s ) o f e n a l a - p r i l i n h e a l t h y s u b j e c t s , d e s i g n e d a n d c o n d u c t e d u n d e r G o o d C l i n i c a l P r a c t i c e g u i d e l i n e s , a s i m i l a r r a t e a n d e x t e n t o f d r u g a b s o r p t i o n f o r b o t h f o r m u l a t i o n s w e r e f o u n d t o b e b i o e q u i v a l e n t . B o t h f o r m u l a t i o n s p r o d u c e d a s i g n i f i c a n t d e - c r e a s e i n B P v a l u e s a n d w e r e g e n e r a l l y w e l l t o l e r a t e d . A C K N O W L E D G M E N T W e t h a n k t h e m e d i c a l , n u r s i n g , a n d a d m i n i s t r a t i v e p e r s o n n e l o f t h e C l i n i c a l P h a r m a c o l o g y S t u d i e s U n i t ( H o s p i t a l C l f n i c o S a n C a r l o s , M a d r i d , S p a i n ) f o r t h e i r e n t h u s i a s t i c c o o p e r a t i o n . REFERENCES 1. C o m m i t t e e for P r o p r i e t a r y Medicinal P r o d u c t s . Note for Guidance on the Investigation o f Bioavailability and Bioequivalence; 2001. Available at: www.emea.eu.int. A c c e s s e d N o v e m b e r 1, 2003. 2. Chow SC, Liu JP. Design and Analysis o f Bioavailability and Bioequivalence Studies. New York: Marcel Dekker; 2000. 3. T o d d PA, Goa KL. Enalapril. A r e a p p r a i s a l of its p h a r m a c o l o g y a n d t h e r a p e u t i c u s e in h y p e r t e n s i o n . Drugs. 1992;43:346-381. 4. Drug Information. B e t h e s d a , Md: A m e r i c a n Hospital F o r m u l a r y Service, A m e r i c a n So- c i e t y of Health-System P h a r m a c i s t s , Inc; 2001. 5. Donnelly R, Meredith PA, Elliott HL, Reid JL. Kinetic-dynamic r e l a t i o n s a n d individual r e s p o n s e s t o enalapril. Hypertension. 1990; 15:301-309. 6. T o d d PA, Heel RC. Enalapril. A r e v i e w of its p h a r m a c o d y n a m i c a n d p h a r m a c o k i n e t i c p r o p e r t i e s , a n d t h e r a p e u t i c u s e in h y p e r t e n s i o n a n d c o n g e s t i v e h e a r t failure. Drugs. 1986;31:198-248. 7. Ribeiro W, M u s c a r ~ MN, Martins AR, et al. B i o e q u i v a l e n c e s t u d y of t w o enalapril m a l e a t e t a b l e t f o r m u l a t i o n s in h e a l t h y m a l e v o l u n t e e r s . P h a r m a c o k i n e t i c v e r s u s p h a r - m a c o d y n a m i c a p p r o a c h . Eur J Clin Pharmacol. 1996;50:399-405. 8. US Food a n d Drug Administration. Guidance for industry: Bioavailability a n d bio- e q u i v a l e n c e s t u d i e s for orally a d m i n i s t e r e d d r u g p r o d u c t s - - G e n e r a l c o n s i d e r a t i o n s . 2003. Available at: www.fda.gov/cder/guidance/index/htm. Accessed N o v e m b e r 1, 2003. A d d r e s s c o r r e s p o n d e n c e t o : A n t o n i o P o r t o l ~ s , MD, P h D , S e r v i c i o d e F a r m a - c o l o g f a C l f n i c a , H o s p i t a l C l f n i c o S a n C a r l o s , c / o P r o f . M a r t f n L a g o s s / n , M a d r i d , S p a i n 28040. E-mail: a p o r t o l e s . h c s c @ s a l u d . m a d r i d . o r g 4 6