[Does oxazepam (ADUMBRAN) interfere with anticoagulant treatment. A controlled study. (author's transl)]

Newer communications dealing with drug interaction between tranquillizers and anticoagulants and the frequent combined intake of these drugs have induced us to perform a series of coagulation-and platelet parameters in 21 antiocoagulated patients with and without oxazepam (Adumbran). Control of adherence to the prescriptions was stressed upon: all cases were controlled by analysis of urin and nonadherent patients were excluded from statistical evaluation of hemostatic parameters. In the obtained well defined group no differences were observed in the effect of constant doses of anticoagulants and different tests of plasmatic coagulation and platelet aggregability.

Selection among benzodiazepines for alcohol withdrawal

Four pharmacologic differences among the benzodiazepines, which are the drugs of choice to conduct alcohol withdrawal, guide selection of the appropriate one: chlordiazepoxide, diazepam, oxazepam, or chlorazepate. Bases for selection include: (1) availability of other than oral dosage forms; (2) differences in additive effect with alcohol in producing central nervous system depression; (3) differences in anticonvulsant effect; and (4) differences in duration of effect in the body (ie, half-life). Decreasing dosage schedules are preferred to a steady dosage. Illustrative dosage schedules for using chlordiazepoxide and diazepam to conduct alcohol withdrawal are given.

First pass conjugation and enterohepatic recycling of oxazepam in dogs; intravenous tolerance of oxazepam in propylene glycol

Oxazepam dissolved in propylene glycol was administered intravenously to dogs. There were no cardiac or general adverse effects. Hemolysis and thrombophlebitis were observed after rapid infusion (5.6 ml in 1 minute), and were shown to be due to the properties of the vehicle. Comparison of plasma concentration time curves after oral and intravenous administration indicated a bioavailability of 70 +/- 15 S.D. %. The decreased availability after oral dose was considered to be due to first pass elimination as the urinary recovery of metabolites was the same after the two routes of administration. This also indicates complete absorption. In a dog with a chronic biliary fistula 15 mg of oxazepam was given intravenously on two occasions. When normal bile flow into the gut was permitted the disposition of oxazepam was similar to that in normal dogs. When bile was withdrawn the elimination of oxazepam was more rapid with an increase of apparent plasma clearance. In this case 32% of the dose was excreted as conjugates in the bile within 3 hours after administration. In the normal dogs 2-20% of the dose given was recovered in the faeces as the parent compound and practically no conjugates were found. These findings indicate enteral hydrolysis of the conjugates, and a marked enterohepatic recycling or oxazepam.

Multiple oral doses of diazepam, oxazepam and phenobarbital to dogs--behavioural effects and correlation with antipyrine half-life

The effects of prolonged treatment with phenobarbital, diazepam, and oxazepam on behaviour and on the plasma half-life of antipyrine have been studied in the dog. In this species the biotransformation of diazepam and oxazepam is known to be very similar to man. After equipotent doses of phenobarbital (25 mg/kg) and diazepam (35 mg/kg), antipyrine half-life was found to decrease 80 and 40%, respectively, while after treatment with oxazepam (150 mg/kg) there was an increase of 20%. The behavioural effects declined in the dogs during the course of treatment with diazepam but were rather constant during treatment with oxazepam.

Disposition of three benzodiazepines after single oral administration in man

Three benzodiazepines in equipotent doses: oxazepam 15 mg, dipotassium chlorazepate 10 mg and diazepam 5 mg, were administered in single, oral doses to seven healthy volunteers in a three-way cross-over study. The serum concentrations of oxazepam, N-desmethyldiazepam and diazepam were followed for 72 hours by gas chromatography and electron capture detection. The absorption of diazepam was most rapid and the mean time required to reach peak serum concentration was 45 minutes, followed by N-desmethyldiazepam 80 minutes and oxazepam 114 minutes. The serum concentration decay curves were biphasic with terminal mean half-lives of 48, 62 and 11 hours for diazepam, N-desmethyldiazepam and oxazepam, respectively. The mean and individual serum concentration time data were fitted to a two-compartment open model with first order absorption using a non linear least square program. The mean serum data fitted the model well. The same rank order was obtained with mean absorption half-lives as when comparing mean peak times while slightly shorter terminal half-lives were obtained in the curve fitting of mean serum data. Due to irregularities in the serum concentration time curves only five out of the 21 sets of individual data could satisfy the convergence criterion. The obtained parameters in the curve fitting were also accompanied with very large asymptotic standard deviations.

Comparative bioavailability of oral dosage forms of oxazepam--correlation with in vitro dissolution rate

Four oxazepam tablet preparations and a suspension of micronized oxazepam in water were given to healthy, fasting volunteers in a comparative bioavailability study using a partial cross-over design. Urinary recovery (0-72 hours) was used as a measure of extent of absorption. Peak serum concentration was used as a measure of rate of absorption. The three dosage forms having the highest dissolution rate in vitro were absorbed to the same extent, while slower dissolving tablets were not as fully absorbed. Peak serum concentration correlated linearly with in vitro dissolution rate. Single oral doses of oxazepam tablets containing 10, 15 and 25 mg showed equal rates and extents of absorption and produced serum concentrations linearly correlated with dose.

Pharmacokinetics of oxazepam in healthy volunteers

The pharmacokinetics of oxazepam was studied in healthy volunteers. When oral doses of 15 mg were given to eight subjects on two occasions 2.5 years apart the individual areas under the plasma concentration time curves did not differ significantly. Plasma clearance ranged between 0.050 and 0.171 x kg-1 x h-1 and half-lives from 5.9 to 25 hours. The urinary recovery of oxazepam conjugates was 67 +/- 15 S.D.% of the dose given and the total recovery including faecal oxazepam was 70 +/- 15 S.D. %. On multiple dosing (5 mg t.i.d.) stable steady-state concentrations were established. There was a tendency for slightly lower steady-state concentrations than predicted from single oral doses. During steady-state 86 +/- 17 S.D. % of the dose was recovered in the urine over a 24 hour period.

Oxazepam disposition in uremic patients

The pharmacokinetics of oxazepam was investigated in 13 uremic patients. The apparent terminal half-life of oxazepam in plasma was 24-91 hours compared to 5.9-25 hours reported elsewhere for healthy volunteers. The plasma concentrations showed secondary peaks about 24 hours after the dose and this probably gave rise to the increase in half-life. Plasma clearance of oxazepam appeared to be normal. The conjugated metabolites accumulated to concentrations 5-50 times those of the parent compound and could still be detected 5 days after a single oral dose (0.2 mg/kg). Renal clearance of conjugated oxazepam was significantly correlated to creatinine clearance. The urinary recovery over 5 days was 18-57%. The faecal recovery of 3 days was 0.1-19%. In some patients up to 49% of oxazepam in faeces was in the conjugated form. It is concluded that enterohepatic recycling of oxazepam might occur in uremic patients but is not of great quantitative importance. During multiple dosing the accumulation of conjugates was even more pronounced, with plasma concentrations amounting to 14-61 times those of oxazepam. Steady-state plasma concentrations of oxazepam was similar to those obtained in normal subjects.

[Pharmacokinetic studies on absorption and excretion of oxazepam in Combination with alcohol (author's transl)]

The influence of 7-chloro-1,3-dihydro-3-hydroxy-5-phenyl 2H-1,4-benzodiazepin-2-one (oxazepam, Adumbran) (30 mg) on the effects produced by alcohol (0.75 g/kg) and vice versa was studied in 14 male test subjects using the following scheme: (A) alcohol; (B) placebo; (C) oxazepam; (D) oxazepam and alcohol combined; (E) alcohol given 30 min prior to oxazepam. Blood and serum levels were determined and excretion in the urine was tested during the 7-h duration of the experiment. The blood alcohol curves show a similar course, leading to the conclusion that oxazepam has no influence on the elimination of alcohol. Alcohol retrads the intestinal absorption of oxazepam but, on the other hand, does not show an effect on the specific metabolism of oxazepam.

Heme catabolism during short-term treatment with phenobarbital, diazepam and oxazepam

Carbon monoxide production (VCO) total body heme (TBH) and serum bilirubin (SB) have been determined in healthy young men before and after 100 mg phenobarbital (10 subjects), 15 mg diazepam (7 subjects) and 75 mg oxazepam (7 subjects), respectively, daily for seven days. None of the drugs had any significant effect on VCO. SB and TBH were also unaffected. Baseline VCO (mean +/- 1 S.E.M.) was 12.6+/-0.6 mumol/mmol TBH and day. The postdrug VCO was 15.1+/-1.8, 14.1+/-1.4 and 14.7+/-1.5 after phenobarbital, diazepam and oxazepam, respectively. The corresponding values for SB were 5.4+/-0.8, 6.0+/-1.5 and 6.2+/-1.0 mug/ml, compared to a baseline value of 6.6+/-0.8 mug/ml. However, when the pooled postdrug data were compared with the pooled baseline values, mean VCO showed a probably significant increase (from 12.6+/-0.6 to 14.7+/-1.0 mumol/mmol TBH and day (p less than 0.05). It is concluded that although phenobarbital is known to increase the hepatic heme turnover, this effect is not measurable in terms of total heme turnover, no more than 20% of which comes from the liver.

Gas chromatographic-mass spectrometric determination of intact C3-hydroxylated benzodiazepine glucoronides in urine

A method is described for the determination C3-hydroxylated benzodiazepine glucuronides in biological samples. Oxazepam and lorazepam glucuronides are measured as methyl esters and trimethylsilyl derivates by a gas chromatographic procedure. The applicability of the method has been tested on the urine of rats, guinea pigs, rabbits and man, receiving oxazepam orally. Oxazepam glucuronide was not found in rat urine but it was present in the urine of rabbits (5.7% of the administered dose), guinea pigs (9.5%) and man (13.4-26.9%).

Benzodiazepines and tricyclic antidepressant plasma levels

Twelve patients acted successfully as subjects to study what effect if any the benzodiazepines nitrazepam, diazepam, oxazepam, and chlordiazepoxide might have on steady-state plasma levels of nortriptyline and amitriptyline. No significant detectable effect was discovered. In view of the known interaction effects of other alternative tranquillizing drugs and hypnotics it seems reasonable to choose benzodiazepines wherever possible when anxiolytics or hypnotics need to be added during treatment of depression with tricyclic antidepressants.