Psychopharmacology (1991) 105:181-185 00333t589100191R
Psychopharmacology © Springer-Verlag 1991
N-desmethyladinazolam pharmacokinetics and behavioral effects following administration of 10-50 mg oral doses in healthy volunteers Joseph C. Fleishaker 1, Thomas C. Smith 2, H. Friedman 2, and J. Paul Phillips 1 1 Clinical Pharmacokinetics Unit, 721524-2, and 2 Clinical Pharmacology Unit, The Upjohn Company Kalamazoo, MI 49007, USA Received June 27, 1990 / Final version February 12, 1991
Abstract. Results of previous studies suggest that Ndesmethyladinazolam, the major metabolite of adinazolam in man, contributes substantially to psychomotor effects and sedation observed following adinazolam administration. Therefore, the pharmacokinetics and pharmacodynamics of N-desmethyladinazolam were explored following administration of single oral doses of placebo and solutions containing 10, 30, and 50 mg N-desmethyladinazolam mesylate in a doubleblind, randomized, four-way crossover design to 15 healthy male volunteers. Plasma concentrations of Ndesmethyladinazolam were determined by HPLC. Psychomotor performance tests (digit symbol substitution and card sorting by fours and suits), memory tests and sedation scoring were also performed following drug administration. N-Desmethyladinazolam pharmacokinetics were dose independent over this range. Doserelated performance effects were observed at 1, 2, and 6 h after dosing. Memory was likewise affected at 2 h. Psychomotor performance decrements correlated with log N-desmethytadinazolam plasma concentrations. Analysis of the relationship between percentage decrements in digit-symbol substitution and plasma Ndesmethyladinazolam using the Hill equation revealed a ECs0 of 325 ng/ml. These results establish the relationship between N-desmethyladinazolam plasma concentrations and performance effects; these data will be helpful in assessing the contribution of N-desmethyladinazolam to clinical effects observed after adinazolam administration. Key words: Mono-N-desmethyladinazotam - Sedation Psychomotor effects Active metabolite - Memory effects
Adinazolam is a triazolobenzodiazepine which exhibits antidepressant properties in preclinical screens (Lahti et Offprint requests to:
J.C. Fleishaker
al. 1983; Turmel and DeMontigny 1984) and exhibits clinical utility in the treatment of depression (Amsterdam et al. 1986; Dunner et al. 1987), genealized anxiety disorder (Sheehan et al. 1990), and panic disorder (Pyke and Greenberg 1989). The major side effects observed upon oral administration in man are sedation and impaired motor coordination. These effects are typical of benzodiazepines, but adinazolam is a rather weak agonist at the benzodiazepine receptor (Sethy et al. 1984). However, mono-N-desmethyladinazolam, the major metabolite of adinazolam in man, is 25 times more potent as a benzodiazepine receptor agonist than is adinazolam (Sethy et al. 1984, 1986). Moreover, N-desmethyladinazolam plasma concentrations after oral administration of adinazolam are higher than those of the parent compound (Peng 1982; Fleishaker and Phillips 1989; Fleishaker et al. 1989a). Therefore, based on preclinical data, it is quite probable that N-desmethyladinazolam significantly contributes to the psychomotor and sedative effects observed after administration of adinazolam in man. The pharmacodynamics of adinazolam and Ndesmethyladinazolam have been studied following 20-60 mg oral doses of adinazolam mesylate in healthy volunteers (Fleishaker and Phillips 1989). Psychomotor effects correlated more closely with plasma Ndesmethyladinazolam concentrations than with those of adinazolam. In a subsequent study, adinazolam and Ndesmethyladinazolam mesylate oral solutions were administered at equivalent doses (10, 30, and 50 mg) in eighteen healthy male volunteers (Fleishaker et al. 1990). Performance effects following adinazolam and Ndesmethyladinazolam treatments at each dose level were quantitatively similar, presumably due to similar plasma N-desmethyladinazolam concentrations at performance testing times. These results support the hypothesis that N-desmethyladinazotam is primarily responsible for the psychomotor effects seen after adinazolam administration; adinazolam contributes little to these effects. In that study, subjects received adinazolam, N-desmethyladinazolam and placebo in a crossover design within doses,
182 b u t subjects were r a n d o m i z e d to receive o n l y one o f the doses. T h e p e r f o r m a n c e d e c r e m e n t s observed after the 30 a n d 5 0 m g doses o f b o t h a d i n a z o l a m a n d N d e s m e t h y l a d i n a z o l a m were n o t significantly different, in c o n t r a s t to the significant differences seen between 40 a n d 6 0 r a g a d i n a z o l a m doses observed previously (Fleishaker a n d Phillips 1989). The lack o f significant differences b e t w e e n results f r o m the highest doses precluded e x p l o r a t i o n o f the r e l a t i o n s h i p between N d e s m e t h y l a d i n a z o l a m c o n c e n t r a t i o n s a n d effects. I n this s t u d y the p h a r m a c o k i n e t i c s a n d p h a r m a c o d y n a m i c s o f N - d e s m e t h y l a d i n a z o l a m at doses u p to 50 m g o f the mesylate salt were assessed i n y o u n g , n o r m a l volunteers. T h e goal was to d e t e r m i n e the dose p r o p o r tionality o f N - d e s m e t h y l a d i n a z o l a m p h a r m a c o k i n e t i c s at these doses a n d to establish the r e l a t i o n s h i p b e t w e e n N - d e s m e t h y l a d i n a z o l a m c o n c e n t r a t i o n s a n d psychom o t o r p e r f o r m a n c e decrements, sedation a n d m e m o r y effects after oral a d m i n i s t r a t i o n .
Materials and methods The clinical portion of the study was conducted at the Upjohn Research Clinics, Kalamazoo, Michigan. Sixteen healthy male volunteers were enrolled. The local Institutional Review Board approved this study, and written informed consent was provided by all subjects prior to enrollment. The mean age of the subjects was 33 years (range 20-46). Mean subject weight was 75.7 kg (range 63.2-91.6). Prior to admission to the study, normal physical examination results, normal clinical laboratory screens, and a negative urine screen for drugs of abuse were documented for each subject. During the 7 days prior to the study and during the study period, subjects received only those medications specified in the protocol. Subjects with hypersensitivity to benzodiazepines were excluded from the study. Each subject received the following treatments according to a balanced 4 × 4 Latin square crossover design. Treatments were A: placebo solution, B: 10 mg N-desmethyladinazolam mesylate, C: 30 mg N-desmethyladinazolam mesylate, and D: 50 mg N-desmethyladinazolam mesylate. The solutions were diluted to the same final volume (50 ml). Both the investigator and subject were blinded as to the treatments administered. Seven days separated day 1 of each study phase. Subjects were admitted to the clinic the evening before drug administration in each phase and released from the clinic following the last blood sample of each phase. Study medications were administered at 8 a.m. on day 1 of each study phase. Study doses were administered with sufficient water to bring the total fluid volume ingested to 180 ml. Subjects were required to fast from 10 h before drug administration until 4 h after the dose. Normal clinic diet was resumed at 4 h after the dose. Diet composition was consistent among the study phases. Subjects remained sedentary during the study period. Venous blood samples were collected immediately before drug administration and at 0.25, 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 8.0, 10.0, 12.0, 16.0, 20.0, and 24.0 h following drug administration. Blood samples (7 ml) were collected at each time into heparinized vacutainers. Plasma was harvested from the samples after centrifugation and frozen until analyzed. Determinations of N-desmethyladinazolam were performed by HPLC (Fteishaker et al. 1989a). Samples from placebo treatment were not analyzed. Psychomotor performance was assessed using the digit-symbol substitution test (Wechsler 1955) and two card sorting tasks : sorting by fours and by suits. The number of correct substitutions in 90 s were measured in the digit-symbol substitution task; the time to complete the card-sorting tasks was quantified. These three tasks were practised three times on the evening before drug administra-
tion in each study phase. Performance tests on the day of drug dosing were administered 30 min prior to and at 1, 2, 6, 8, and 12 h after dosing. At each blood sampling time, sedation was rated by an observer according to the five-point Nurse Rated Sedation Scale (Smith and Kroboth 1987). Scale values were: 0--wide awake, l=awake but lethargic, 2=dozing, eyes closed but not asleep, 3 = sleeping soundly, awakened by blood draw, 4 = sleeping soundly, did not waken during sample collection. Memory was assessed at 2 and 8 h after dosing by a modification of the Randt memory test (Randt and Brown 1983).
Data analysis. Pharmacokinetic parameters were determined using noncompartmental techniques (Gibaldi and Perrier 1982). The terminal elimination rate constant (K~0 was determined by linear regression of the terminal portion of the log concentration-time profile. Area under the plasma concentration-time curve up to the last measurable drug concentration was calculated by trapezoidal rule and extrapolated to infinity. Apparent oral clearance (Clo) was calculated as Dose/AUC. Apparent volume of distribution (Vd/F) was calculated as Clo/Kel. Maximal concentrations (Cma~)and the times at which they occurred (Tmax) were determined directly from the data. Differences in pharmacokinetic parameters among doses were assessed using analysis of variance (ANOVA) for a crossover design. Type IV sums of squares were used to assess model effects in ANOVA, and least squares means analysis was used to assess differences in pharmacokinetic parameters between individual treatments. Percent changes in psychomotor performance were calculated relative to the zero hour determination during each phase. Differences in performance effects among treatments were assessed using repeated measures ANOVA; pair-wise comparisons among treatments and times were made using least squares means analysis. Maximal sedation scores, the area under the sedation score curve from 0 to 12 h (AUCs), and memory test results were compared among treatments using ANOVA. Correlations between percent decrements in psychomotor performance and log N-desmethyladinazolam plasma concentrations were explored by simple linear regression. The relationship between N-desmethyladinazolam plasma concentrations and decrements in digit-symbol substitution test score were also explored by fitting a sigmoidal E=~xmodel to the data, using the following equation (Juhl 1988) : E --
Em~C~ EC~0 "~Cs
where E=,~ is the absolute value of the maximal change in performance, C is the plasma concentration of N-desmethyladinazolam, ECso is the plasma concentration of N-desmethyladinazolam at half maximal effect, and s is a correction factor related to the shape of the dose response curve. The nonlinear teast squares estimation program NLIN (SAS Institute 1985) was used for parameter estimation.
Results Sixteen patients were enrolled in a n d started this trial. Subject 4 was w i t h d r a w n f r o m the study after the second phase, due to the ingestion o f p r e s c r i p t i o n m e d i c a t i o n to treat a stiff neck a n d shoulder, in v i o l a t i o n o f the p r o t o col. T h e results r e p o r t e d here p e r t a i n to the r e m a i n i n g 15 subjects. M e a n 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 are s u m m a r i z e d in T a b l e 1. N - d e s m e t h y l a d i n a z o l a m A U C a n d Cmax values increased p r o p o r t i o n a l l y with dose; there were n o signific a n t differences in Clo, C1° corrected for b o d y weigt, Ke~, V d / F , or v o l u m e corrected for b o d y weight. Tmax was likewise unaffected b y the dose administered.
183 Table 1. Mean (_+standard deviation) N-desmethyladinazolam pharmacokinetic parameters following administration of 10, 30, and 50 mg doses of N-desmethyladinazolam mesytate in 15 healthy male volunteers
Dose (rag)
10
AUC (ng h/ml) AUC NORM" (ng h/ml) Clo (l/h)
500* 1510* (69.4) (231) 500 503 (69.4) (77.2) 15.9 15.9 (2.03) (2.41) 0.210 0.210 (0.030) (0.041) 165" 494* (39.3) (107) 165 165 (39.3) (35.8) 0.767 0.567 (0.320) (0.176) 0.224 0.228 (0.019) (0.028) 3.12 3.08 (0.263) (0.383) 71.3 69.8 (9.29) (9.71) 0.940 0.923 (0.119) (0.151)
Clo (1/h/kg) Cmax (ng/mt) Cmax NORM" (ng/ml) Tmax (h) Kel (h- ~) ta/z (h) Vd/F (1) Vd/F (1/kg)
30
50 2474* (311) 495 (62.3) 16.0 (2.01) 0.212 (0.031) 781" (187) 156 (37.5) 0.750 (0.661) 0.229 (0.023) 3.06 (0.299) 70.5 (10.4) 0.93I (0.136)
Normalized to a 10 mg dose * Values for 10, 30, and 50 mg doses are significantly different from one another at P
Psychopharmacology © Springer-Verlag 1991
N-desmethyladinazolam pharmacokinetics and behavioral effects following administration of 10-50 mg oral doses in healthy volunteers Joseph C. Fleishaker 1, Thomas C. Smith 2, H. Friedman 2, and J. Paul Phillips 1 1 Clinical Pharmacokinetics Unit, 721524-2, and 2 Clinical Pharmacology Unit, The Upjohn Company Kalamazoo, MI 49007, USA Received June 27, 1990 / Final version February 12, 1991
Abstract. Results of previous studies suggest that Ndesmethyladinazolam, the major metabolite of adinazolam in man, contributes substantially to psychomotor effects and sedation observed following adinazolam administration. Therefore, the pharmacokinetics and pharmacodynamics of N-desmethyladinazolam were explored following administration of single oral doses of placebo and solutions containing 10, 30, and 50 mg N-desmethyladinazolam mesylate in a doubleblind, randomized, four-way crossover design to 15 healthy male volunteers. Plasma concentrations of Ndesmethyladinazolam were determined by HPLC. Psychomotor performance tests (digit symbol substitution and card sorting by fours and suits), memory tests and sedation scoring were also performed following drug administration. N-Desmethyladinazolam pharmacokinetics were dose independent over this range. Doserelated performance effects were observed at 1, 2, and 6 h after dosing. Memory was likewise affected at 2 h. Psychomotor performance decrements correlated with log N-desmethytadinazolam plasma concentrations. Analysis of the relationship between percentage decrements in digit-symbol substitution and plasma Ndesmethyladinazolam using the Hill equation revealed a ECs0 of 325 ng/ml. These results establish the relationship between N-desmethyladinazolam plasma concentrations and performance effects; these data will be helpful in assessing the contribution of N-desmethyladinazolam to clinical effects observed after adinazolam administration. Key words: Mono-N-desmethyladinazotam - Sedation Psychomotor effects Active metabolite - Memory effects
Adinazolam is a triazolobenzodiazepine which exhibits antidepressant properties in preclinical screens (Lahti et Offprint requests to:
J.C. Fleishaker
al. 1983; Turmel and DeMontigny 1984) and exhibits clinical utility in the treatment of depression (Amsterdam et al. 1986; Dunner et al. 1987), genealized anxiety disorder (Sheehan et al. 1990), and panic disorder (Pyke and Greenberg 1989). The major side effects observed upon oral administration in man are sedation and impaired motor coordination. These effects are typical of benzodiazepines, but adinazolam is a rather weak agonist at the benzodiazepine receptor (Sethy et al. 1984). However, mono-N-desmethyladinazolam, the major metabolite of adinazolam in man, is 25 times more potent as a benzodiazepine receptor agonist than is adinazolam (Sethy et al. 1984, 1986). Moreover, N-desmethyladinazolam plasma concentrations after oral administration of adinazolam are higher than those of the parent compound (Peng 1982; Fleishaker and Phillips 1989; Fleishaker et al. 1989a). Therefore, based on preclinical data, it is quite probable that N-desmethyladinazolam significantly contributes to the psychomotor and sedative effects observed after administration of adinazolam in man. The pharmacodynamics of adinazolam and Ndesmethyladinazolam have been studied following 20-60 mg oral doses of adinazolam mesylate in healthy volunteers (Fleishaker and Phillips 1989). Psychomotor effects correlated more closely with plasma Ndesmethyladinazolam concentrations than with those of adinazolam. In a subsequent study, adinazolam and Ndesmethyladinazolam mesylate oral solutions were administered at equivalent doses (10, 30, and 50 mg) in eighteen healthy male volunteers (Fleishaker et al. 1990). Performance effects following adinazolam and Ndesmethyladinazolam treatments at each dose level were quantitatively similar, presumably due to similar plasma N-desmethyladinazolam concentrations at performance testing times. These results support the hypothesis that N-desmethyladinazotam is primarily responsible for the psychomotor effects seen after adinazolam administration; adinazolam contributes little to these effects. In that study, subjects received adinazolam, N-desmethyladinazolam and placebo in a crossover design within doses,
182 b u t subjects were r a n d o m i z e d to receive o n l y one o f the doses. T h e p e r f o r m a n c e d e c r e m e n t s observed after the 30 a n d 5 0 m g doses o f b o t h a d i n a z o l a m a n d N d e s m e t h y l a d i n a z o l a m were n o t significantly different, in c o n t r a s t to the significant differences seen between 40 a n d 6 0 r a g a d i n a z o l a m doses observed previously (Fleishaker a n d Phillips 1989). The lack o f significant differences b e t w e e n results f r o m the highest doses precluded e x p l o r a t i o n o f the r e l a t i o n s h i p between N d e s m e t h y l a d i n a z o l a m c o n c e n t r a t i o n s a n d effects. I n this s t u d y the p h a r m a c o k i n e t i c s a n d p h a r m a c o d y n a m i c s o f N - d e s m e t h y l a d i n a z o l a m at doses u p to 50 m g o f the mesylate salt were assessed i n y o u n g , n o r m a l volunteers. T h e goal was to d e t e r m i n e the dose p r o p o r tionality o f N - d e s m e t h y l a d i n a z o l a m p h a r m a c o k i n e t i c s at these doses a n d to establish the r e l a t i o n s h i p b e t w e e n N - d e s m e t h y l a d i n a z o l a m c o n c e n t r a t i o n s a n d psychom o t o r p e r f o r m a n c e decrements, sedation a n d m e m o r y effects after oral a d m i n i s t r a t i o n .
Materials and methods The clinical portion of the study was conducted at the Upjohn Research Clinics, Kalamazoo, Michigan. Sixteen healthy male volunteers were enrolled. The local Institutional Review Board approved this study, and written informed consent was provided by all subjects prior to enrollment. The mean age of the subjects was 33 years (range 20-46). Mean subject weight was 75.7 kg (range 63.2-91.6). Prior to admission to the study, normal physical examination results, normal clinical laboratory screens, and a negative urine screen for drugs of abuse were documented for each subject. During the 7 days prior to the study and during the study period, subjects received only those medications specified in the protocol. Subjects with hypersensitivity to benzodiazepines were excluded from the study. Each subject received the following treatments according to a balanced 4 × 4 Latin square crossover design. Treatments were A: placebo solution, B: 10 mg N-desmethyladinazolam mesylate, C: 30 mg N-desmethyladinazolam mesylate, and D: 50 mg N-desmethyladinazolam mesylate. The solutions were diluted to the same final volume (50 ml). Both the investigator and subject were blinded as to the treatments administered. Seven days separated day 1 of each study phase. Subjects were admitted to the clinic the evening before drug administration in each phase and released from the clinic following the last blood sample of each phase. Study medications were administered at 8 a.m. on day 1 of each study phase. Study doses were administered with sufficient water to bring the total fluid volume ingested to 180 ml. Subjects were required to fast from 10 h before drug administration until 4 h after the dose. Normal clinic diet was resumed at 4 h after the dose. Diet composition was consistent among the study phases. Subjects remained sedentary during the study period. Venous blood samples were collected immediately before drug administration and at 0.25, 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 8.0, 10.0, 12.0, 16.0, 20.0, and 24.0 h following drug administration. Blood samples (7 ml) were collected at each time into heparinized vacutainers. Plasma was harvested from the samples after centrifugation and frozen until analyzed. Determinations of N-desmethyladinazolam were performed by HPLC (Fteishaker et al. 1989a). Samples from placebo treatment were not analyzed. Psychomotor performance was assessed using the digit-symbol substitution test (Wechsler 1955) and two card sorting tasks : sorting by fours and by suits. The number of correct substitutions in 90 s were measured in the digit-symbol substitution task; the time to complete the card-sorting tasks was quantified. These three tasks were practised three times on the evening before drug administra-
tion in each study phase. Performance tests on the day of drug dosing were administered 30 min prior to and at 1, 2, 6, 8, and 12 h after dosing. At each blood sampling time, sedation was rated by an observer according to the five-point Nurse Rated Sedation Scale (Smith and Kroboth 1987). Scale values were: 0--wide awake, l=awake but lethargic, 2=dozing, eyes closed but not asleep, 3 = sleeping soundly, awakened by blood draw, 4 = sleeping soundly, did not waken during sample collection. Memory was assessed at 2 and 8 h after dosing by a modification of the Randt memory test (Randt and Brown 1983).
Data analysis. Pharmacokinetic parameters were determined using noncompartmental techniques (Gibaldi and Perrier 1982). The terminal elimination rate constant (K~0 was determined by linear regression of the terminal portion of the log concentration-time profile. Area under the plasma concentration-time curve up to the last measurable drug concentration was calculated by trapezoidal rule and extrapolated to infinity. Apparent oral clearance (Clo) was calculated as Dose/AUC. Apparent volume of distribution (Vd/F) was calculated as Clo/Kel. Maximal concentrations (Cma~)and the times at which they occurred (Tmax) were determined directly from the data. Differences in pharmacokinetic parameters among doses were assessed using analysis of variance (ANOVA) for a crossover design. Type IV sums of squares were used to assess model effects in ANOVA, and least squares means analysis was used to assess differences in pharmacokinetic parameters between individual treatments. Percent changes in psychomotor performance were calculated relative to the zero hour determination during each phase. Differences in performance effects among treatments were assessed using repeated measures ANOVA; pair-wise comparisons among treatments and times were made using least squares means analysis. Maximal sedation scores, the area under the sedation score curve from 0 to 12 h (AUCs), and memory test results were compared among treatments using ANOVA. Correlations between percent decrements in psychomotor performance and log N-desmethyladinazolam plasma concentrations were explored by simple linear regression. The relationship between N-desmethyladinazolam plasma concentrations and decrements in digit-symbol substitution test score were also explored by fitting a sigmoidal E=~xmodel to the data, using the following equation (Juhl 1988) : E --
Em~C~ EC~0 "~Cs
where E=,~ is the absolute value of the maximal change in performance, C is the plasma concentration of N-desmethyladinazolam, ECso is the plasma concentration of N-desmethyladinazolam at half maximal effect, and s is a correction factor related to the shape of the dose response curve. The nonlinear teast squares estimation program NLIN (SAS Institute 1985) was used for parameter estimation.
Results Sixteen patients were enrolled in a n d started this trial. Subject 4 was w i t h d r a w n f r o m the study after the second phase, due to the ingestion o f p r e s c r i p t i o n m e d i c a t i o n to treat a stiff neck a n d shoulder, in v i o l a t i o n o f the p r o t o col. T h e results r e p o r t e d here p e r t a i n to the r e m a i n i n g 15 subjects. M e a n 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 are s u m m a r i z e d in T a b l e 1. N - d e s m e t h y l a d i n a z o l a m A U C a n d Cmax values increased p r o p o r t i o n a l l y with dose; there were n o signific a n t differences in Clo, C1° corrected for b o d y weigt, Ke~, V d / F , or v o l u m e corrected for b o d y weight. Tmax was likewise unaffected b y the dose administered.
183 Table 1. Mean (_+standard deviation) N-desmethyladinazolam pharmacokinetic parameters following administration of 10, 30, and 50 mg doses of N-desmethyladinazolam mesytate in 15 healthy male volunteers
Dose (rag)
10
AUC (ng h/ml) AUC NORM" (ng h/ml) Clo (l/h)
500* 1510* (69.4) (231) 500 503 (69.4) (77.2) 15.9 15.9 (2.03) (2.41) 0.210 0.210 (0.030) (0.041) 165" 494* (39.3) (107) 165 165 (39.3) (35.8) 0.767 0.567 (0.320) (0.176) 0.224 0.228 (0.019) (0.028) 3.12 3.08 (0.263) (0.383) 71.3 69.8 (9.29) (9.71) 0.940 0.923 (0.119) (0.151)
Clo (1/h/kg) Cmax (ng/mt) Cmax NORM" (ng/ml) Tmax (h) Kel (h- ~) ta/z (h) Vd/F (1) Vd/F (1/kg)
30
50 2474* (311) 495 (62.3) 16.0 (2.01) 0.212 (0.031) 781" (187) 156 (37.5) 0.750 (0.661) 0.229 (0.023) 3.06 (0.299) 70.5 (10.4) 0.93I (0.136)
Normalized to a 10 mg dose * Values for 10, 30, and 50 mg doses are significantly different from one another at P
