Life Sciences, Vol. 51, pp. 1739-1746 Printed in the USA
THE
Pergamon Press
PRESENCE OF COCAINE AND BENZOYLECGONINE IN RAT CEREBROSPINAL FLUID AFTER THE INTRAVENOUS ADMINISTRATION OF COCAINE
Edward
J.
B a r b i e r i I, A n d r e w P. Ferko, G. J o h n and E i l e e n K. R u c h
DiGregorio,
D e p a r t m e n t of P h a r m a c o l o g y H a h n e m a n n U n i v e r s i t y , S c h o o l of M e d i c i n e Philadelphia, Pennsylvania (Received in final form September 23, 1992) Summary
Cocaine hydrochloride, in d o s e s of 0.5, 1.0, 2.0 and 4.0 mg/kg, iv, w a s a d m i n i s t e r e d to m a l e S p r a g u e - D a w l e y rats. C e r e b r o s p i n a l f l u i d (CSF) w a s c o l l e c t e d f r o m the c i s t e r n a m a g n a o v e r a 20 m i n p e r i o d and b l o o d s a m p l e s w e r e o b t a i n e d at 20 m i n a f t e r c o c a i n e a d m i n i s t r a t i o n . In a d d i t i o n , b l o o d s a m p l e s for the 1 m g / k g d o s e of c o c a i n e w e r e c o l l e c t e d at 2, I0, 20 and 30 m i n f o l l o w i n g d r u g injection. Gas chromatography/mass s p e c t r o m e t r y w a s u s e d for t h e a n a l y s i s of c o c a i n e and its m e t a b o l i t e s in p l a s m a and CSF. The disappearance of cocaine (i mg/kg) from the plasma e x h i b i t e d first o r d e r k i n e t i c s w i t h a h a l f - l i f e of 18.11 ± 3.22 min. C o c a i n e and b e n z o y l e c g o n i n e w e r e f o u n d in C S F and the concentrations of c o c a i n e and b e n z o y l e c g o n i n e i n c r e a s e d in CSF as the d o s e s of c o c a i n e w e r e increased. C S F f l o w r a t e s w e r e not a l t e r e d by the iv a d m i n i s t r a t i o n of c o c a i n e or b e n z o y l e c g o n i n e . The C S F - t o - p l a s m a r a t i o s for c o c a i n e w e r e q u i t e s i m i l a r to e a c h o t h e r o v e r the d o s a g e r a n g e of c o c a i n e t h a t w a s a d m i n i s t e r e d ; however, t h e C S F - t o - p l a s m a r a t i o s for b e n z o y l e c g o n i n e d e c r e a s e d as the c o n c e n t r a t i o n s of b e n z o y l e c g o n i n e i n c r e a s e d in p l a s m a a n d CSF. When benzoylecgonine (2 mg/kg, iv) w a s given, the compound was detected in CSF indicating that b e n z o y l e c g o n i n e can e n t e r into the c e n t r a l n e r v o u s s y s t e m f r o m the p e r i p h e r a l blood. This i n v e s t i g a t i o n s h o w s t h a t c o c a i n e and b e n z o y l e c g o n i n e can be a s s a y e d in CSF and t h a t the p l a s m a levels of t h e s e c o m p o u n d s c o r r e l a t e w i t h t h e i r concentrations in CSF. The distribution of c o c a i n e into a v a r i e t y of t i s s u e s has b e e n r e p o r t e d by s e v e r a l i n v e s t i g a t o r s (1-4). S i n c e m a n y of the e f f e c t s of c o c a i n e are r e l a t e d to its a c t i v i t y on the c e n t r a l n e r v o u s s y s t e m (CNS), t h e r e is i n c r e a s i n g i n t e r e s t in the c o n c e n t r a t i o n s of t h i s drug of abuse that accumulate in the brain following its administration.
iCorrespondence to: E d w a r d J. Barbieri, Ph.D., P h a r m a c o l o g y , H a h n e m a n n U n i v e r s i t y School of M e d i c i n e , P e n n s y l v a n i a 19102.
D e p a r t m e n t of Philadelphia,
0024-3205/92 $5.00 + .00 Copyright © 1992 Pergamon Press Ltd All rights reserved.
1740
Cocaine and Benzoylecgonine in Rat CSF
Vol. 51, No. 22, 1992
I n v e s t i g a t o r s who have p u b l i s h e d data w h i c h show the p r e s e n c e of cocaine or cocaine metabolites in the homogenized brains of e x p e r i m e n t a l animals have used r e l a t i v e l y large doses of c o c a i n e to o b t a i n their results. For example, Nayak et al (i) r e p o r t e d that c o c a i n e could be d e t e c t e d in rat b r a i n 15 m i n u t e s f o l l o w i n g a single iv i n j e c t i o n of 8 m g / k g of 3H-cocaine and 30 m i n u t e s after an ip injection of the same dose. Shah et al (2) d e s c r i b e d the d e t e c t i o n of cocaine in the brains of p r e g n a n t and n o n p r e g n a n t female mice 15 m i n u t e s after the i n t r a p e r i t o n e a l a d m i n i s t r a t i o n of 3H-cocaine, i0 mg/kg. Both r a d i o l a b e l e d cocaine and polar m e t a b o l i t e s w e r e assayed in rat brain within 30 minutes of iv injection or oral a d m i n i s t r a t i o n of i0 m g / k g of 3H-cocaine (3). Cocaine was assayed in m a t e r n a l and fetal brain tissue, using high p e r f o r m a n c e liquid c h r o m a t o g r a p h y (HPLC), following the ip a d m i n i s t r a t i o n of 30 m g / k g to p r e g n a n t rats (4). Recently, Ferko et al (5,6) showed that cocaine and cocaine m e t a b o l i t e s could be assayed by gas c h r o m a t o g r a p h y / m a s s s p e c t r o m e t r y (GC/MS) in a v a r i e t y of biological fluids from rats, including plasma, urine, p a r o t i d saliva and amniotic fluid, using small doses of cocaine. B a s e d on the p r e v i o u s l y cited work in w h i c h a single dose of c o c a i n e was used and as an a l t e r n a t i v e to h o m o g e n i z e d brain (which r e p r e s e n t s a m i x t u r e of brain tissue, interstitial fluid, and some c e r e b r o s p i n a l fluid), it was important to examine a r e l a t i v e l y pure b i o l o g i c a l sample from the CNS, i.e., cerebrospinal fluid (CSF), of rats t r e a t e d with various doses of cocaine, for the p r e s e n c e of cocaine and its m e t a b o l i t e s by GC/MS.
Methods Animals. M a l e S p r a g u e - D a w l e y rats (200 - 225 g) were o b t a i n e d from C h a r l e s Rivers Laboratories, Inc. (Wilmington, MA) and were housed for 1 w e e k prior to e x p e r i m e n t a t i o n at 22 ± 1 °C with a light cycle from 6:00 AM to 6:00 PM. The animals had free access to Purina R o d e n t L a b o r a t o r y Chow 5001 (Ralston Purina Co., St. Louis, MO) and water. S u r g i c a l Procedures. Rats were a n e s t h e t i z e d w i t h p e n t o b a r b i t a l sodium (Nembutal, A b b o t t Laboratories, North Chicago, IL), 50 mg/kg, ip. The trachea was c a n n u l a t e d with p o l y e t h y l e n e tubing (P.E. 240) to ensure a clear airway. The left femoral vein was c a n n u l a t e d with p o l y e t h y l e n e t u b i n g (P.E. 60) for intravenous injection and the left femoral artery was c a n n u l a t e d with b e v e l e d P.E. 60 t u b i n g for the c o l l e c t i o n of blood samples. For the c o l l e c t i o n of CSF from the c i s t e r n a magna, the animal was placed on its ventral side, an incision was made in the skin at the back of the head, and the levator auris longus m u s c l e was cut. From the m i d p o i n t of the i n t e r p a r i e t a l - o c c i p i t a l junction, a 23 gauge needle was inserted at a p o i n t 6 mm down (perpendicularly); the needle was p l a c e d at a depth of 8 mm to enter the cisterna magna. Micro-hematocrit c a p i l l a r y tubes (75 mm) were a t t a c h e d to the end of the needle to collect CSF for a 20 minute p e r i o d after the iv injection of cocaine hydrochloride.
Cocaine Experiment.
The a n e s t h e t i z e d animals were injected iv with saline or one of the following doses of cocaine h y d r o c h l o r i d e (Mallinckrodt, Paris, Kentucky): 0.50, 1.0, 2.0 and 4.0 mg/kg. In order to c a l c u l a t e p h a r m a c o k i n e t i c p a r a m e t e r s of cocaine in the plasma, blood samples for the 1.0 m g / k g dose were c o l l e c t e d at 2,
Vol. 51, No. 22, 1992
Cocaine and Benzoylecgonine in Rat CSF
1741
i0, 20, and 30 min following drug administration. Blood samples for the other doses of cocaine were collected at 20 min after the iv injection of cocaine. Blood samples were c o l l e c t e d in 1.5 mL p o l y e t h y l e n e centrifuge tubes (Brinkman Instruments, Inc., Westbury, N.Y.) c o n t a i n i n g 30 mg of sodium fluoride to p r e v e n t the loss of cocaine due to hydrolysis (7) and 30 units of h e p a r i n sodium to prevent the c o a g u l a t i o n of blood. A single CSF sample was collected at 0 to 20 min after cocaine a d m i n i s t r a t i o n and placed in a p o l y e t h y l e n e tube containing sodium fluoride. In a related experiment, benzoylecgonine h y d r o c h l o r i d e (Research T e c h n o l o g y Branch of NIDA, Rockville, MD) was a d m i n i s t e r e d iv in a dose of 2.0 mg/kg, to determine if an iv injection of this compound would enter the CSF; a blood sample was collected 20 min later. In addition, a CSF sample was obtained over the 20 min period following the injection of benzoylecgonine hydrochloride.
Sample Preparation and Analysis.
The blood sample was centrifuged at 2000 x g for i0 min and the plasma removed. In the assay i00 ~L of plasma and 50 ~L of CSF were used, to which was added 500 ng of the internal standard for the GC/MS analysis, scopolamine. (Further details d e s c r i b i n g sample p r e p a r a t i o n and d e r i v a t i z a t i o n with MSTFA ( N - m e t h y l - N - t r i m e t h y l s i l y l t r i f l u o r o a c e t a m i d e , Pierce Chemical Co., Rockford, IL) have been previously reported (5). Reagents and solvents used in the extraction procedure were of analytical grade. The analysis for cocaine, benzoylecgonine, norcocaine, and ecgonine methyl ester in plasma and CSF was done by gas c h r o m a t o g r a p h y / m a s s spectrometry (GC/MS). The GC/MS system was a V a r i a n 3400 gas c h r o m a t o g r a p h / F i n n e g a n MAT ion trap detector. The analytical p r o c e d u r e has been p r e v i o u s l y reported (5). Standards of cocaine, benzoylecgonine, ecgonine methyl ester, and n o r c o c a i n e were obtained from the Research T e c h n o l o g y Branch of NIDA (Rockville, MD). Cocaine and the MSFTA derivatives of benzoylecgonine, ecgonine methyl ester, and n o r c o c a i n e exhibited r e t e n t i o n times of 513, 557, 233 and 637 sec., respectively. The internal standard, the MSTFA derivative of scopolamine, had a r e t e n t i o n time of 619 sec on the chromatogram. The recoveries (mean ± S.D. of 14 samples) for cocaine and b e n z o y l e c g o n i n e were 95.4 ± 6.3 and 90.2 ± 6.8 %, respectively, when they were extracted from plasma. In addition a commercial control for b e n z o y l e c g o n i n e (Bio Rad Lyphocheck, Urine (human) Toxicology Control) was analyzed; the c o n c e n t r a t i o n of benzoylecgonine in the control was listed as 425 ng/mL and our results showed 416.9 ± 5.9 ng/mL (N = 40).
Calculations
and Statistics. The p h a r m a c o k i n e t i c p a r a m e t e r s for cocaine were d e t e r m i n e d using standard p h a r m a c o k i n e t i c m a t h e m a t i c a l c a l c u l a t i o n s as used by Khan et al (8). First-order elimination data were graphed by the least square method. Statistically s i g n i f i c a n t d i f f e r e n c e s in grouped data were d e t e r m i n e d by analysis of variance (ANOVA). Multiple comparisons of groups were analyzed by A N O V A followed by the Dunnett's Test. Results The plasma c o n c e n t r a t i o n s of cocaine and b e n z o y l e c g o n i n e following the injection of cocaine hydrochloride (i.0 mg/kg, iv) are illustrated in Figure 1. The d i s a p p e a r a n c e of cocaine from the
1742
Cocaine and Benzoylecgonine in Rat CSF
Vol. 51, No. 22, 1992
plasma followed first order kinetics and the calculated p h a r m a c o k i n e t i c p a r a m e t e r s of t h i s c o m p o u n d a r e p r e s e n t e d in T a b l e i. s i n c e t h e c o n c e n t r a t i o n s of b e n z o y l e c g o n i n e in p l a s m a r e m a i n e d
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THE
Pergamon Press
PRESENCE OF COCAINE AND BENZOYLECGONINE IN RAT CEREBROSPINAL FLUID AFTER THE INTRAVENOUS ADMINISTRATION OF COCAINE
Edward
J.
B a r b i e r i I, A n d r e w P. Ferko, G. J o h n and E i l e e n K. R u c h
DiGregorio,
D e p a r t m e n t of P h a r m a c o l o g y H a h n e m a n n U n i v e r s i t y , S c h o o l of M e d i c i n e Philadelphia, Pennsylvania (Received in final form September 23, 1992) Summary
Cocaine hydrochloride, in d o s e s of 0.5, 1.0, 2.0 and 4.0 mg/kg, iv, w a s a d m i n i s t e r e d to m a l e S p r a g u e - D a w l e y rats. C e r e b r o s p i n a l f l u i d (CSF) w a s c o l l e c t e d f r o m the c i s t e r n a m a g n a o v e r a 20 m i n p e r i o d and b l o o d s a m p l e s w e r e o b t a i n e d at 20 m i n a f t e r c o c a i n e a d m i n i s t r a t i o n . In a d d i t i o n , b l o o d s a m p l e s for the 1 m g / k g d o s e of c o c a i n e w e r e c o l l e c t e d at 2, I0, 20 and 30 m i n f o l l o w i n g d r u g injection. Gas chromatography/mass s p e c t r o m e t r y w a s u s e d for t h e a n a l y s i s of c o c a i n e and its m e t a b o l i t e s in p l a s m a and CSF. The disappearance of cocaine (i mg/kg) from the plasma e x h i b i t e d first o r d e r k i n e t i c s w i t h a h a l f - l i f e of 18.11 ± 3.22 min. C o c a i n e and b e n z o y l e c g o n i n e w e r e f o u n d in C S F and the concentrations of c o c a i n e and b e n z o y l e c g o n i n e i n c r e a s e d in CSF as the d o s e s of c o c a i n e w e r e increased. C S F f l o w r a t e s w e r e not a l t e r e d by the iv a d m i n i s t r a t i o n of c o c a i n e or b e n z o y l e c g o n i n e . The C S F - t o - p l a s m a r a t i o s for c o c a i n e w e r e q u i t e s i m i l a r to e a c h o t h e r o v e r the d o s a g e r a n g e of c o c a i n e t h a t w a s a d m i n i s t e r e d ; however, t h e C S F - t o - p l a s m a r a t i o s for b e n z o y l e c g o n i n e d e c r e a s e d as the c o n c e n t r a t i o n s of b e n z o y l e c g o n i n e i n c r e a s e d in p l a s m a a n d CSF. When benzoylecgonine (2 mg/kg, iv) w a s given, the compound was detected in CSF indicating that b e n z o y l e c g o n i n e can e n t e r into the c e n t r a l n e r v o u s s y s t e m f r o m the p e r i p h e r a l blood. This i n v e s t i g a t i o n s h o w s t h a t c o c a i n e and b e n z o y l e c g o n i n e can be a s s a y e d in CSF and t h a t the p l a s m a levels of t h e s e c o m p o u n d s c o r r e l a t e w i t h t h e i r concentrations in CSF. The distribution of c o c a i n e into a v a r i e t y of t i s s u e s has b e e n r e p o r t e d by s e v e r a l i n v e s t i g a t o r s (1-4). S i n c e m a n y of the e f f e c t s of c o c a i n e are r e l a t e d to its a c t i v i t y on the c e n t r a l n e r v o u s s y s t e m (CNS), t h e r e is i n c r e a s i n g i n t e r e s t in the c o n c e n t r a t i o n s of t h i s drug of abuse that accumulate in the brain following its administration.
iCorrespondence to: E d w a r d J. Barbieri, Ph.D., P h a r m a c o l o g y , H a h n e m a n n U n i v e r s i t y School of M e d i c i n e , P e n n s y l v a n i a 19102.
D e p a r t m e n t of Philadelphia,
0024-3205/92 $5.00 + .00 Copyright © 1992 Pergamon Press Ltd All rights reserved.
1740
Cocaine and Benzoylecgonine in Rat CSF
Vol. 51, No. 22, 1992
I n v e s t i g a t o r s who have p u b l i s h e d data w h i c h show the p r e s e n c e of cocaine or cocaine metabolites in the homogenized brains of e x p e r i m e n t a l animals have used r e l a t i v e l y large doses of c o c a i n e to o b t a i n their results. For example, Nayak et al (i) r e p o r t e d that c o c a i n e could be d e t e c t e d in rat b r a i n 15 m i n u t e s f o l l o w i n g a single iv i n j e c t i o n of 8 m g / k g of 3H-cocaine and 30 m i n u t e s after an ip injection of the same dose. Shah et al (2) d e s c r i b e d the d e t e c t i o n of cocaine in the brains of p r e g n a n t and n o n p r e g n a n t female mice 15 m i n u t e s after the i n t r a p e r i t o n e a l a d m i n i s t r a t i o n of 3H-cocaine, i0 mg/kg. Both r a d i o l a b e l e d cocaine and polar m e t a b o l i t e s w e r e assayed in rat brain within 30 minutes of iv injection or oral a d m i n i s t r a t i o n of i0 m g / k g of 3H-cocaine (3). Cocaine was assayed in m a t e r n a l and fetal brain tissue, using high p e r f o r m a n c e liquid c h r o m a t o g r a p h y (HPLC), following the ip a d m i n i s t r a t i o n of 30 m g / k g to p r e g n a n t rats (4). Recently, Ferko et al (5,6) showed that cocaine and cocaine m e t a b o l i t e s could be assayed by gas c h r o m a t o g r a p h y / m a s s s p e c t r o m e t r y (GC/MS) in a v a r i e t y of biological fluids from rats, including plasma, urine, p a r o t i d saliva and amniotic fluid, using small doses of cocaine. B a s e d on the p r e v i o u s l y cited work in w h i c h a single dose of c o c a i n e was used and as an a l t e r n a t i v e to h o m o g e n i z e d brain (which r e p r e s e n t s a m i x t u r e of brain tissue, interstitial fluid, and some c e r e b r o s p i n a l fluid), it was important to examine a r e l a t i v e l y pure b i o l o g i c a l sample from the CNS, i.e., cerebrospinal fluid (CSF), of rats t r e a t e d with various doses of cocaine, for the p r e s e n c e of cocaine and its m e t a b o l i t e s by GC/MS.
Methods Animals. M a l e S p r a g u e - D a w l e y rats (200 - 225 g) were o b t a i n e d from C h a r l e s Rivers Laboratories, Inc. (Wilmington, MA) and were housed for 1 w e e k prior to e x p e r i m e n t a t i o n at 22 ± 1 °C with a light cycle from 6:00 AM to 6:00 PM. The animals had free access to Purina R o d e n t L a b o r a t o r y Chow 5001 (Ralston Purina Co., St. Louis, MO) and water. S u r g i c a l Procedures. Rats were a n e s t h e t i z e d w i t h p e n t o b a r b i t a l sodium (Nembutal, A b b o t t Laboratories, North Chicago, IL), 50 mg/kg, ip. The trachea was c a n n u l a t e d with p o l y e t h y l e n e tubing (P.E. 240) to ensure a clear airway. The left femoral vein was c a n n u l a t e d with p o l y e t h y l e n e t u b i n g (P.E. 60) for intravenous injection and the left femoral artery was c a n n u l a t e d with b e v e l e d P.E. 60 t u b i n g for the c o l l e c t i o n of blood samples. For the c o l l e c t i o n of CSF from the c i s t e r n a magna, the animal was placed on its ventral side, an incision was made in the skin at the back of the head, and the levator auris longus m u s c l e was cut. From the m i d p o i n t of the i n t e r p a r i e t a l - o c c i p i t a l junction, a 23 gauge needle was inserted at a p o i n t 6 mm down (perpendicularly); the needle was p l a c e d at a depth of 8 mm to enter the cisterna magna. Micro-hematocrit c a p i l l a r y tubes (75 mm) were a t t a c h e d to the end of the needle to collect CSF for a 20 minute p e r i o d after the iv injection of cocaine hydrochloride.
Cocaine Experiment.
The a n e s t h e t i z e d animals were injected iv with saline or one of the following doses of cocaine h y d r o c h l o r i d e (Mallinckrodt, Paris, Kentucky): 0.50, 1.0, 2.0 and 4.0 mg/kg. In order to c a l c u l a t e p h a r m a c o k i n e t i c p a r a m e t e r s of cocaine in the plasma, blood samples for the 1.0 m g / k g dose were c o l l e c t e d at 2,
Vol. 51, No. 22, 1992
Cocaine and Benzoylecgonine in Rat CSF
1741
i0, 20, and 30 min following drug administration. Blood samples for the other doses of cocaine were collected at 20 min after the iv injection of cocaine. Blood samples were c o l l e c t e d in 1.5 mL p o l y e t h y l e n e centrifuge tubes (Brinkman Instruments, Inc., Westbury, N.Y.) c o n t a i n i n g 30 mg of sodium fluoride to p r e v e n t the loss of cocaine due to hydrolysis (7) and 30 units of h e p a r i n sodium to prevent the c o a g u l a t i o n of blood. A single CSF sample was collected at 0 to 20 min after cocaine a d m i n i s t r a t i o n and placed in a p o l y e t h y l e n e tube containing sodium fluoride. In a related experiment, benzoylecgonine h y d r o c h l o r i d e (Research T e c h n o l o g y Branch of NIDA, Rockville, MD) was a d m i n i s t e r e d iv in a dose of 2.0 mg/kg, to determine if an iv injection of this compound would enter the CSF; a blood sample was collected 20 min later. In addition, a CSF sample was obtained over the 20 min period following the injection of benzoylecgonine hydrochloride.
Sample Preparation and Analysis.
The blood sample was centrifuged at 2000 x g for i0 min and the plasma removed. In the assay i00 ~L of plasma and 50 ~L of CSF were used, to which was added 500 ng of the internal standard for the GC/MS analysis, scopolamine. (Further details d e s c r i b i n g sample p r e p a r a t i o n and d e r i v a t i z a t i o n with MSTFA ( N - m e t h y l - N - t r i m e t h y l s i l y l t r i f l u o r o a c e t a m i d e , Pierce Chemical Co., Rockford, IL) have been previously reported (5). Reagents and solvents used in the extraction procedure were of analytical grade. The analysis for cocaine, benzoylecgonine, norcocaine, and ecgonine methyl ester in plasma and CSF was done by gas c h r o m a t o g r a p h y / m a s s spectrometry (GC/MS). The GC/MS system was a V a r i a n 3400 gas c h r o m a t o g r a p h / F i n n e g a n MAT ion trap detector. The analytical p r o c e d u r e has been p r e v i o u s l y reported (5). Standards of cocaine, benzoylecgonine, ecgonine methyl ester, and n o r c o c a i n e were obtained from the Research T e c h n o l o g y Branch of NIDA (Rockville, MD). Cocaine and the MSFTA derivatives of benzoylecgonine, ecgonine methyl ester, and n o r c o c a i n e exhibited r e t e n t i o n times of 513, 557, 233 and 637 sec., respectively. The internal standard, the MSTFA derivative of scopolamine, had a r e t e n t i o n time of 619 sec on the chromatogram. The recoveries (mean ± S.D. of 14 samples) for cocaine and b e n z o y l e c g o n i n e were 95.4 ± 6.3 and 90.2 ± 6.8 %, respectively, when they were extracted from plasma. In addition a commercial control for b e n z o y l e c g o n i n e (Bio Rad Lyphocheck, Urine (human) Toxicology Control) was analyzed; the c o n c e n t r a t i o n of benzoylecgonine in the control was listed as 425 ng/mL and our results showed 416.9 ± 5.9 ng/mL (N = 40).
Calculations
and Statistics. The p h a r m a c o k i n e t i c p a r a m e t e r s for cocaine were d e t e r m i n e d using standard p h a r m a c o k i n e t i c m a t h e m a t i c a l c a l c u l a t i o n s as used by Khan et al (8). First-order elimination data were graphed by the least square method. Statistically s i g n i f i c a n t d i f f e r e n c e s in grouped data were d e t e r m i n e d by analysis of variance (ANOVA). Multiple comparisons of groups were analyzed by A N O V A followed by the Dunnett's Test. Results The plasma c o n c e n t r a t i o n s of cocaine and b e n z o y l e c g o n i n e following the injection of cocaine hydrochloride (i.0 mg/kg, iv) are illustrated in Figure 1. The d i s a p p e a r a n c e of cocaine from the
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Cocaine and Benzoylecgonine in Rat CSF
Vol. 51, No. 22, 1992
plasma followed first order kinetics and the calculated p h a r m a c o k i n e t i c p a r a m e t e r s of t h i s c o m p o u n d a r e p r e s e n t e d in T a b l e i. s i n c e t h e c o n c e n t r a t i o n s of b e n z o y l e c g o n i n e in p l a s m a r e m a i n e d
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