Hypnotic accumulation and hangover in elderly inpatients: a controlled double-blind study of temazepam and nitrazepam

The hypnotic and residual sedative effects of the first and seventh of seven regular night-time doses of nitrazepam 5 mg, temazepam 20 mg, and placebo were studied in 58 elderly inpatients. Plasma temazepam and nitrazepam concentrations rose by about 50% and 113% respectively between the mornings of day 1 and day 7. Patients reported sleeping well more often after the first dose of either hypnotic (p less than 0.05), but there was no difference after the seventh dose. Reaction time was unchanged on the morning after the first dose but was significantly prolonged after the seventh dose of both hypnotics (p less than 0.01). The time taken to eliminate the letter E from a page of prose tended to be prolonged after the first dose of both drugs (temazepam v placebo, p less than 0.05; nitrazepam v placebo, not significant) and was further prolonged on the morning after the seventh dose of nitrazepam (nitrazepam v placebo, p less than 0.05). Thus plasma accumulation of the drug was associated with a deterioration in daytime performance. This change in performance did not correlate with age, cerebral blood flow, or plasma concentration, but patients of low intelligence tended to be more severely affected.

Pharmacokinetics of benzodiazepine hypnotics

Three benzodiazepine derivatives are currently indicated specifically for the treatment of insomnia in the United States. Flurazepam is biotransformed to at least two rapidly appearing and rapidly eliminated intermediate metabolites which probably contribute to sleep induction. The final metabolite, desalkylflurazepam, appears slowly, but has a long half-life ranging from 40 to 150 h. This metabolite accumulates extensively during multiple dosage. Temazepam is a slowly absorbed drug and has an intermediate half-life in the range of 10-20 h. Triazolam has an intermediate absorption rate, but is rapidly eliminated (half-life 1.5-5 h) making it essentially non-accumulating. Understanding of the pharmacokinetics of benzodiazepine hypnotics can contribute to understanding of their clinical properties.

Aging and drug disposition--pharmacodynamics

The pharmacodynamics of a drug is defined as the effect of the drug on physiological functions and pathological processes and can be modified in the elderly by (a) pharmacokinetics, (b) receptor sensitivity (or density), (c) impaired homeostasis or (d) pathology. The alterations in pharmacokinetics in the elderly often result in a reduction of the dose required to achieve the optimum pharmacodynamic effect. Changes in the sensitivity of receptors may be decreased in the elderly (perhaps by a diminution in the number of receptors) as in the case of the beta-adrenergic blockers, but increase in sensitivity may also be found as in the case of warfarin. Impairment of homeostatic mechanisms, while related to aging, are frequently produced by pathological processes and have an important influence on the pharmacodynamics of many drugs. The effect of the multiple pathology often found in the elderly is likely to be the dominant factor in changes in pharmacodynamics in this population. The interaction of the above factors results in a heterogeneity of pharmacodynamic response in the elderly which requires the careful monitoring of both the efficacy and toxicity of their drug treatment.

Temazepam (Restoril, Sandoz Pharmaceuticals)

Temazepam is a benzodiazepine derivative indicated for the treatment of insomnia. Pharmacokinetic studies of the hard capsule formulation indicate that the mean time to peak is 2.99 hours and the mean elimination half-life is 14.7 hours. Sleep laboratory studies have demonstrated improvements in all sleep parameters except sleep onset latency. Clinically, patients report improvements in all sleep parameters including sleep onset latency. The efficacy of temazepam compares favorably with barbiturates, glutethimide, nitrazepam, lorazepam, oxazepam, and flurazepam. It has not been compared with diazepam in the clinical setting. Side effects include drowsiness, dizziness, and lethargy. The incidence of hangover effects from 15- and 30-mg doses is relatively low. Temazepam has no proven advantages over other benzodiazepine hypnotics. The major issues that need further clarification include temazepam's sleep induction properties and the relative incidence of hangover and rebound insomnia when compared with longer-acting benzodiazepines.

Estimating the fraction reabsorbed in drugs undergoing enterohepatic circulation

A simple method of estimating the extent of biliary recycling using blood level and cumulative biliary excretion data from control and bile duct-cannulated animals is described. The method was tested in rats following an intravenous dose of [14C] temazepam. It was shown that 62% of the drug excreted in the bile of control rats was reabsorbed during each enterohepatic cycle, contributing to the secondary peak blood concentrations and a prolonged elimination half-life.

A practical method for monitoring drug excretion and enterohepatic circulation in the rat

An improved experimental design for studying the enterohepatic circulation of drugs in a pair of bile duct-duodenum cannula-linked rats is described. By housing the rats in individual metabolism cages and using a peristaltic pump to immediately deliver bile secreted by the donor directly into the duodenum of the recipient, the method permits a realistic approximation of biliary excretion and reabsorption in intact animals for periods up to 96 hours.

Effect of age and gender on disposition of temazepam

Thirty-two male and female volunteers, 24-84 years of age, ingested single 30-mg doses of temazepam, a 3-hydroxy-1,4-benzodiazepine derivative used as a hypnotic agent. Kinetics of total and unbound temazepam were determined from multiple plasma temazepam concentrations measured during 48 hr after the dose. The temazepam elimination half-life ranged from 8 to 38 hr and was longer in women than in men (16.8 versus 12.3 hr, p less than 0.05). Likewise, clearance of total temazepam (assuming complete absorption) was higher in men than in women (1.35 versus 1.02 ml/min/kg, p less than 0.025). Neither half-life nor clearance was significantly related to age. The volume of distribution of total temazepam (mean 1.40 liters/kg) was unrelated to age or gender. Temazepam was extensively protein bound, with a mean free fraction of 2.6% (range 12.7-3.4%). The free fraction increased with age (r = 0.45, p = 0.01), partly due to the inverse relation of the free fraction to plasma albumin concentration (r = -0.34, p = 0.06) and the age-related decline in plasma albumin (r = -0.49, p less than 0.005). After correction for individual differences in binding, clearance of unbound temazepam in men was higher than in women (50.5 versus 39.7 ml/min/kg, 0.05 less than p less than 0.01), and it tended to decline with age in both sexes (r = -0.44 and -0.43, respectively, p = 0.1).

Evaluation of temazepam as a hypnotic

Temazepam is a 1,4-benzodiazepine, newly marketed in the United States for the symptomatic treatment of the complaint of insomnia. The manufacturer recommends a dose of 30 mg before bedtime for most adults and 15 mg for geriatric or debilitated patients. A dose of 30 mg usually produces peak plasma concentrations within 3 hours after oral ingestion and has a mean half-life of 10 to 15 hours. Thus, temazepam is absorbed more slowly and metabolized more quickly than flurazepam, the only other benzodiazepine marketed in the United States specifically for insomnia. Eight sleep laboratory and 21 clinical studies on temazepam indicate that temazepam reduces awakening during the night and increases sleep duration. However, there was no consistent evidence that temazepam reduces sleep latency--probably because temazepam, taken at bedtime, does not reach sufficiently high blood levels in time to affect sleep onset. One sleep laboratory study on 8 insomniac patients given 35 consecutive nightly doses of 30 mg found no evidence of tolerance or rebound insomnia. Studies on tolerance, metabolism and carry-over effects have shown that temazepam has no long-acting metabolites and does not affect waking function following use at bedtime. In patients for whom hypnotic medication is appropriate, temazepam should be an effective drug for reducing most symptoms of insomnia.

Temazepam: a review of its pharmacological properties and therapeutic efficacy as an hypnotic

Temazepam is a benzodiazepine drug which is a minor metabolite of diazepam. In clinical studies using subjective evaluation methods it was effective for maintaining sleep and increasing total sleep time. However, sleep laboratory studies did not show a significant effect on some sleep parameters, especially sleep induction. Temazepam has a relatively short half-life (about 5 to 11 hours, longer in some subjects and in the elderly), and no active metabolites of clinical importance, and thus may be considered more suitable for use as an hypnotic than longer acting drugs such as diazepam, nitrazepam or flurazepam when residual sedative effects the next day are not desirable. Indeed, few residual effects on morning performance appear to occur with usual single doses of temazepam, although at the upper end of the recommended dosage range (30 mg or more) some evidence of impaired psychomoter and cognitive function in the morning has been reported. Whether or not temazepam is likely to produce "hangover" with repeated night-time administration needs further clarification. While a call for a large number of controlled trials may not be justifiable in evaluating a new hypnotic, a few well designed additional comparative studies in insomniac subjects are needed to assess adequately the relative merits of temazepam (particularly with regard to sleep onset) compared with other benzodiazepine hypnotics, especially those which are short- or intermediate-acting.

Bioavailability of temazepam in soft gelatin capsules

1 Healthy volunteers received single doses of temazepam 30 mg in conventional gelatin capsules, suppositories or in solution. They experienced marked sedation and sleepiness. The onset of sleepiness was prompt after the administration of the solution; this latter showed the fastest absorption and gave the highest peak plasma levels. This observation led to the development of the soft gelatin capsule. 2 To assess bioavailability of the formulation, plasma levels of temazepam were determined in healthy volunteers after single oral administration of soft and hard capsules, and after seven consecutive night-time doses of the soft capsule. Absorption from the soft gelatin capsule was faster and produced earlier and higher peak plasma levels. There were no differences in relative availability. 3 The apparent half-life of temazepam after night-time administration was shorter than after morning administration, but no change was observed between the first and seventh night-time doses.

Pharmacokinetics and metabolism of temazepam in man and several animal species

1 Absorption, excretion and detoxification of temazepam were investigated in man, mouse, rat and dog. Considerable interspecies variation was apparent with respect to excretion and metabolite patterns in blood and urine. Animal species were exposed to equal or greater concentrations of all the metabolites occurring in man. 2 Pharmacokinetics of temazepam in man were investigated in a single dose study at two dose levels, and in a multiple dose study. The results of both studies were analyzed and interpreted with the help of compartmental models. Values were obtained for excretion pattern (0-infinity), half lives (1.95, 0.5, 10.0 and 1.9 h), amounts in all compartments, and for steady-state conditions. 3 The bioavailability of the hard gelatin capsule dosage form was compared with that of a suspension serving as the ideal dosage form, and found to be acceptable.

Distribution of camazepam in rats and mice

Camazepam, 5 mg/kg iv, was injected in rats and mice to study its distribution in the blood and brain. Peak blood levels were about 0.9 microgram/ml in rats and 0.6 microgram/ml in mice. Peak brain levels were about 1.5 microgram/g in rats and 0.8 microgram/g in mice. The apparent blood half-life of camazepam was 9 min in mice and 20 min in rats.