Claude B. Coutinho

Relationship between the duration of anticonvulsant activity of chlordiazepoxide and systemic levels of the parent compound and its major metabolites in mice.

Abstract The duration of the anticonvulsant (antimetrazol) activity of chlordiazepoxide in mice in relation to blood levels and tissue distribution patterns of the parent drug and its major metabolites is presented. Quantitation of the effect of a 125 mg/kg s.c. injection of metrazol and the degree of protection by a single 20 mg/kg oral dose of chlordiazepoxide, based on measuring the incidence of defined seizure reactions, indicated maximal protection for 4 hr after chlordiazepoxide administration. The quantitative 14C distribution after the oral administration of a single 20 mg/kg dose of chlordiazepoxide-2-14C is indicative of a rapid absorption onset as well as of a gradual increase in the tissue-to-blood 14C ratios from 0.5 to 6 hr after administration. In contrast, a 125 mg/kg subcutaneous injection of metrazol given 30 min after the oral administration of chlordiazepoxide appears both to reduce markedly the rate of absorption and to alter the disposition of chlordiazepoxide. This alteration includes a reduction in the blood 14C and tissue 14C levels immediately after metrazol injection to 4 hr after chlordiazepoxide administration. Although the initial tissue-to-blood 14C ratios are similar to those seen in the absence of metrazol, they do not show the marked increment with time. Differential spectrofluorometric analyses of blood, brain and muscle tissue samples for chlordiazepoxide and its major metabolites show that N-desmethylchlordiazepoxide is the major constituent in all three tissues both in the absence and in the presence of metrazol. Besides being present in much higher concentrations, unlike the parent compound and other metabolites, the N-desmethyl derivative maintains a maximum level from 30 min to 4 hr in the brain and from 30 min to 6 hr in blood and muscle. Correlation of the levels of chlordiazepoxide and its metabolites in these tissues to its anticonvulsant (antimetrazol) activity indicates that it is the concentration of the N-desmethyl metabolite that most closely parallels the pattern of this anticonvulsant activity.

The absorption and biotransformation of pentaerythritol tetranitrate- 1,214C by rats

Abstract Radioactive pentaerythritol tetranitrate (PETN) was administered orally to rats, and its absorption, tissue distribution, and excretion were followed at specified time intervals. By applying thin-layer chromatography and radio-scanning techniques, the four transformation products of PETN were identified and assayed quantitatively in the blood, selected tissues, and excreta. PETN was absorbed at a moderate rate and quickly cleared from the blood by the tissues. The degradation of PETN proceeded in the gastrointestinal tract, in the blood, and in tissues. The extent of PETN degradation was greatest in the liver, spleen, lungs, heart, and blood. Pentaerythritol and its mononitrate were the principal urinary metabolites.

Correlation between the duration of the anticonvulsant activity of diazepam and its physiological disposition in mice

Abstract A correlation between the duration of the anticonvulsant activity of diaze- pam [7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one (Ro 5-2807)] and the physiological disposition of the intact drug and three metabolites—(1) the N -demethylated derivative [7-chloro-1,3-dihydro-5-phenyl-2H-1,4-benzodiazepin-2-one (Ro 5-2180)], (2) the hydroxylated derivative [7-chloro-1,3-dihydro-3-hydroxy-1-methyl-5-phenyl-2H-1, 4-benzodiazepin-2-one (Ro 5-5345)], and (3) oxazepam [7-chloro-1 ,3-dihydro-3-hydroxy-5-phenyl-2H-1, 4-benzodiazepin-2-one (Ro 5-6789)]—in mice is presented. Maximal protection for 6 hr against a standard 125 mg/kg s.c. convulsant dose of metrazol was afforded by a single 2.5 mg/kg oral dose of diazepam. Quantitative 3 H distribution after the oral administration of a single 2.5 mg/kg dose of diazepam- 3 H shows rapid absorption and a rapid increase over 1–30 min in the tissue-to-blood 3 H ratios of the brain, muscle, heart, fat and carcass. These ratios thereafter increase gradually or remain constant to 4 hr after drug administration. A 125 mg/kg s.c. injection of metrazol given 30 min after the oral administration of diazepam does not significantly affect the tissue-to-blood 3 H ratios nor does it alter the 3 H disposition, except between 4 and 6 hr, during which time a definite increase in the total 3 H concentration of the blood, brain and muscle is observed. This increase is reflected in an increase in the concentration of the parent compound and of the products of its hydroxylation and desmethylation in blood, brain and muscle. Differential analyses of blood, brain and muscle tissue samples for diazepam and three of its major metabolites (Ro 5-2180, Ro 5-5345 and Ro 5-6789) from 30 min to 24 hr show that, although the concentration of each component at 30 min is similar both in the absence and presence of metrazol, a definite shift in the slope of the fall-off patterns toward a slower rate of disappearance of the parent compound and of its hydroxylated and desmethylated derivatives is evident when the administration of diazepam is followed by a subcutaneous injection of metrazol. The major constituent in all three tissues, both in the absence and presence of metrazol, is the end product of metabolism, namely oxazepam (Ro 5-6789). Besides being present in much higher concentrations, unlike the parent compound and the other metabolites, Ro 5-6789 maintains a fairly constant level in all three tissues from 30 min to 12 hr and then gradually falls to 24 hr. Although the contribution of the parent compound and its hydroxylated derivative to the duration and degree of protection cannot be accurately defined, it appears that the degree of protection to the convulsant action of metrazol is most closely related to the rate of disappearance of the N -desmethyl derivative.

Chlordiazepoxide metabolism as related to the reduction in the aggressive behaviour of cynomolgus primates.

1. Blood levels and tissue distribution of chlordiazepoxide and its major metabolites have been correlated with observed changes in ‘aggression” and ‘activity” following oral administration of the compound to cynomolgus (Macaca fascicularis) primates.2. Distribution of 14C after a single oral dose of [2-14C] chlordiazepoxide (5 mg/kg) is indicative of rapid absorption, approximately 30% and 80% dose being absorbed by 0.25 h and 2 h respectively. Highest blood concentrations are observed 2-6 h after dosing. The relatively high content of 14C in the tissues and the corresponding low content in urine and faeces at 2-12 h after dosing are suggestive of tissue storage and/or enterohepatic recirculation.3. Analysis of blood, brain and muscle for chlordiazepoxide and its major metabolites indicate that these are present 0.25 h after dosing. Chlordiazepoxide and its N-desmethylated derivative reach peak concentrations in all three tissues 2 h after dosing while the peak for ‘lactam” is attained at 6 h. In all 3 t...

Behavioural Changes in Primates and Diazepam Metabolism

Abstract1. Changes in ‘aggression’ and ‘activity’ observed in cynomolgus primates (Macaca fascicularis) following administration of a single 2·5 mg/kg oral dose of diazepam have been related to blood levels and tissue distribution of the parent compound and its major metabolites.2. Distribution of 14C after a single oral dose of [2-14C]diazepam shows rapid absorption, 75% of the dose being absorbed by 2 h at which time highest blood concn. are observed. With the exception of muscle and carcass, tissue-to-blood ratios exceed 1·0 throughout 24 h. High 14C content in excreta between 2 and 12 h after dosing suggests hepatic recycling and/or tissue storage.3. Analyses of blood, brain and muscle from 0·25 to 24 h after dosing show the presence of diazepam and its major metabolites as early as 0·25 h after dosing, the N-desmethyl derivative predominating throughout the 24 h period. The concn. of diazepam in all three tissues falls relatively faster than its metabolites.4. Max. reduction in ‘aggression’ (79%) and...