Early responses of the liver of B6C3F1 mice to the hepatocarcinogen oxazepam

Oxazepam has recently been shown to induce hepatocarcinogenicity in B6C3F1 mice. Due to the widespread human exposure to this anxiolytic compound and other structurally similar benzodiazepines, we conducted toxicity and cell proliferation studies on oxazepam to determine possible mechanisms whereby this nonmutagenic chemical may have exerted a carcinogenic effect. Male B6C3F1 mice (10 per dose-time group) received diets containing oxazepam at 0, 25, 125, 2500, and 5000 ppm. Mice were treated for 15, 30, 45, or 90 days, at which time they were evaluated for feed consumption, liver/body weight ratios, clinical pathology, serum oxazepam levels, and histopathology of the liver. During the final 7 days before sacrifice, the mice were exposed to BrDU via osmotic minipump to quantify hepatocellular replicative DNA synthesis. Few effects were observed resulting from chronic exposure to oxazepam other than statistically significant, dose-related increases in liver/body weight ratios. Replicative DNA synthesis was significantly increased in a dose-related manner at the 15-day time point in the 125, 2500, and 5000 ppm dose groups, and attained levels of four- to five-fold above control levels which returned to control levels by 30 days. The lack of significant toxicity, sustained increased liver/body weight ratios, and the rapid and transient induction of replicative DNA synthesis are similar to the effects reported for exposure to another widely used therapeutic agent shown to be a nongenotoxic carcinogen, phenobarbital.

Pain sensation in transurethral microwave thermotherapy for benign prostatic hyperplasia: the rationale for prophylactic sedation

Transurethral microwave thermotherapy (TUMT) can be painful. Pain sensation limits treatment tolerance and consequently also treatment efficacy. Of our population of patients treated with TUMT, 22% (63/288) needed intravenous analgesia and, nevertheless, 6% (17/288) needed definitive treatment interruption. The aim of this study was to identify the mechanism of pain sensation during TUMT and to verify whether the prophylactic use of a sedative drug would improve treatment tolerance. Eighty-three patients undergoing TUMT treatment for benign prostatic hyperplasia at our department entered a prospective, randomized, single-blinded study. Thirty minutes before treatment, 40 patients (group A) received 960 mg cotrimoxazole orally while 43 patients (group B) received 960 mg cotrimoxazole and 10 mg oxazepam, both orally. Statistically significant improvement in treatment tolerance in group B in comparison with group A was found. Pain sensation during TUMT seemed to be mostly due to anxiety. It is concluded that the prophylactic use of a sedative drug is advisable in patients undergoing TUMT in order to improve treatment tolerance.

An investigation of micronucleus and mutation induction by oxazepam in mammalian cells

The benzodiazepines are a class of drugs that are widely used in the treatment of various psychiatric disorders. One member of this class, oxazepam, is also a common metabolite of several other benzodiazepines. Since the evidence for the genetic toxicity and carcinogenic properties of these compounds is inconsistent, we investigated the oxazepam-induced formation of micronuclei in Syrian Hamster embryo fibroblast (SHE) cells, human amniotic fluid fibroblast-like (AFFL) cells and L5178Y mouse cells. A dose-dependent increase in micronucleus fractions was found in all three cell lines. The time course of micronucleus induction in L5178Y cells showed a maximum at 5 h after treatment, suggesting that the micronuclei were formed in the first mitosis after treatment. Kinetochore staining (CREST-antiserum) revealed the presence of kinetochores in approximately 50% of the micronuclei in all three cell types. This result was further confirmed by in situ hybridization in L5178Y cells and indicates the presence of whole chromosomes or centric fragments as well as acentric fragments in the oxazepam-induced micronuclei. The L5178Y cells did not show a mutagenic response to oxazepam at any of the doses or expression times used.

Modeling blood/plasma concentrations in dosed feed and dosed drinking water toxicology studies

A computer model for predicting blood/plasma concentrations of test chemicals in dosed feed and dosed drinking water toxicology studies was developed. The model was constructed based on linear theory. The animal's feeding and drinking habits and the linear disposition kinetics of the test chemical obtained after a bolus gavage dose were built into the model. Blood/plasma concentrations of oxazepam and pentachlorophenol in dosed feed and dosed drinking water studies were predicted and compared with the experimentally determined data. The model proved highly reliable in predicting the blood/plasma concentrations of test chemical in dosed feed and dosed drinking water studies. The results suggest that if the kinetics of test chemicals fit a one-compartment model then bioaccumulation of the test chemical will occur in dosed feed or in dosed drinking water studies when absorption half-lives are less than 1.38 hr and elimination half-lives are longer than 5 hr. The extent of accumulation is mainly dependent on the elimination half-lives. For chemicals with absorption half-lives less than 1.38 hr and elimination half-lives less than 2 hr, the extent of bioaccumulation will be minimal. Blood/plasma concentrations of test chemicals in rats and mice will fluctuate daily and a quasi-steady state will be achieved after ad libitum exposure to dosed feed or dosed drinking water for approximately 4 days. If a daily 12-hr light cycle is used with the light cycle starting at 7:00 AM, the expected peak and trough blood concentrations in dosed feed studies will occur approximately in the early morning (5:00 AM) and in the late afternoon (4:00 PM), respectively. Similar results were obtained for dosed drinking water studies. The model should be applicable to dosed feed and dosed drinking water studies using other species.

Oral benzodiazepines and conscious sedation: A review

A large number of benzodiazepines have been studied for use as sedatives and for their anxiolytic potential as premedicants for outpatient surgery. Potent, new, orally-administered drugs with short half-lives, rapid onset, and minimal residual effects have been developed. Dose-dependent amnesia is also produced by some of these agents. Advances in understanding receptor physiology have shed light on specific pharmacologic activities and aided the discovery of benzodiazepine antagonists with antidote properties. While these drugs have relatively low toxicity, dose-related oversedation remains a risk in susceptible patients, especially when combined with other sedatives.

Pharmacodynamics of the anticonvulsant effect of oxazepam in aging BN/BiRij rats

1. The purpose of this investigation was to examine the influence of increasing age on the pharmacokinetics and the time course of the anticonvulsant response of oxazepam in BN/BiRij rats as an animal model of aging. 2. Oxazepam was administered intravenously in a dose of 12 mg kg-1 body weight and the anticonvulsant effect intensity was measured as elevation above baseline of a threshold for induction of localized seizure activity (TLS). Direct cortical stimulation with ramp shaped electrical pulse trains of increasing intensity was used to determine this threshold. 3. The pharmacological effect vs. time profile showed in young rats an anticonvulsant component followed by proconvulsant component which is suggestive for the occurrence of acute tolerance and/or withdrawal syndrome. With increasing age the proconvulsant component disappeared, resulting in a monophasic effect profile (anticonvulsant effect only) at the age of 35 months with significantly higher anticonvulsant effect intensity immediately following drug administration. No age-related changes in the pharmacokinetic parameters of oxazepam were observed. 4. In five animals of each age group, benzodiazepine receptor binding characteristics were determined in vitro with [3H]-flunitrazepam as a ligand. Both receptor density and affinity did not show age-related changes. Available literature data on post-receptor events do not indicate conclusive age-related changes. 5. It is concluded, that the observed change in the pharmacodynamics of anticonvulsant effect of oxazepam can be explained by the disappearance of the tolerance/withdrawal phenomenon. This is compatible with a decreased efficiency of homeostatic control mechanisms in the elderly.

Correlation between doses of oxazepam and their effects on performance of a standardised test battery

Ten different doses of oxazepam (ranging from 7.5 to 50 mg) or placebo were administered to a total of 28 female subjects in three separate studies. Subjects completed a battery of psychometric tests at 1 and 2 h postdose. The tests included critical flicker fusion, choice reaction time and a tracking task. Following separate analyses of variance, effect sizes (Cohen's d) were calculated for each dose at each dependent variable. These effect sizes were then correlated with the dose of drug administered, using regression analyses. It was found that the doses correlated highly with most of the psychometric variables determined, implying that the test battery is sensitive to drug effects.

Neurodevelopment in late infancy after prenatal exposure to benzodiazepines--a prospective study

Growth and neurodevelopment at 6, 10 and 18 months of age have been studied prospectively and longitudinally in a series of 17 children born to mothers who used benzodiazepines (BZD) in therapeutic doses as their only psychotropic drug throughout pregnancy. The results were compared with a group of 29 children born to mothers without any known use of psychotropic drugs. The BZD-exposed children caught up their low mean birth-weight, at an early stage, whereas the slightly decreased head circumference at birth remained at the same low level. In five infants, a pattern of craniofacial anomalies was found. Deviating neurodevelopmental and clinical symptoms and signs were common. The gross motor development was retarded at 6 and 10 months, but was nearly normal at 18 months. Impaired fine motor functions were found on all follow-up occasions. At 18 months, the most prominent finding was a delayed development of pincer grasp. The BZD-exposed children showed deviations in muscle tone and pattern of movements more frequently than children in the reference group. The study suggests that the use of BZD in therapeutic doses throughout pregnancy can have negative effects on the development of children up to 18 months of age. The long-term hazards cannot be evaluated from these results. A further follow-up at early school age is needed and is in progress.

Mortality in Swiss albino mice after i.p. injection of oxazepam in dimethyl sulphoxide

Twenty percent of the Swiss albino mice administered with a single dose (60 mg/kg) of oxazepam dissolved in dimethyl sulphoxide (DMSO) died within 7 days. Similarly high mortality rate (37%) was observed in diazepam sensitive mice derived from a Swiss albino stock. In contrast, zero mortality was observed in Swiss albino mice administered with DMSO or diazepam (35 mg/kg). Mortality at 60 mg/kg diazepam was only 10%. The high mortality caused by oxazepam in Swiss albino mice seemed to be strain-related as only 7% mortality was observed with identically treated BALB/c mice. Since DMSO is the only convenient vehicle for the administration of oxazepam by injection, it is suggested that a suitable strain must be selected for experimentation in order to avoid unnecessary loss of animals.

Single dose pharmacokinetics and pharmacodynamics of oral oxazepam in very elderly institutionalised subjects

The effect of extreme old age on the pharmacokinetics and pharmacodynamics of orally administered oxazepam 15 mg was studied in 10 healthy elderly (age 80-94 years) institutionalised subjects and 10 healthy young controls (age 26-42 years). The total oxazepam clearance was 1.24 (0.91-1.80) ml min-1 kg-1 (median and range) and 1.44 (0.88-2.13) ml min-1 kg-1 in the elderly and young, respectively (NS), and the elimination half-lives were 8.1 (5.5-10.8) h and 5.7 (4.9-6.2) h. respectively (P less than 0.01). The percent of unbound oxazepam was greater in the elderly; 9.8 (8.1-13.3)% as opposed to 5.1 (3.7-5.9)% in the young (P less than 0.0001). Clearance of unbound oxazepam was lower in the elderly, median values being 13.8 (7.1-21.1) ml min-1 kg-1 compared with 30.3 (18.3-41.5) ml min-1 kg-1 in the young (P less than 0.0001). A single 15 mg dose oxazepam decreased the ability of the elderly to perform a finger tapping test at 3 h but not 8 h after drug administration, whereas placebo had no effect at either times. No effect was observed in the young subjects.

Prenatal oxazepam enhances mouse maternal aggression in the offspring, without modifying acute chlordiazepoxide effects

In the rat, behavioral changes during lactation are in several ways similar to those produced by benzodiazepines (BDZ). Moreover, an increased activity at the GABA/BDZ receptor complex has been found in both conditions. We tested the hypothesis that early manipulation of this neurochemical system by prenatal BDZ exposure should affect typical responses of lactating dams, such as maternal aggression. Outbred CD-1 mice were treated with either oxazepam (15 mg/kg PO twice/day on days 12-16 of fetal life) or vehicle and fostered at birth to untreated dams. Female offspring were subsequently mated at the young-adult stage and used to assess maternal aggressive responses towards a male intruder. In a first 5-min test on postpartum day 6, the prenatal oxazepam animals showed a reduced Latency to the First Attack, a markedly enhanced frequency of several offensive scores (such as Fighting Episodes, Attacks, and Offensive Upright, On Top, and Kicking Postures), a decrease of Submissive Postures and a reduced duration of time spent lying still (Out of the Nest). The tests were repeated 48 h later after IP treatment by either chlordiazepoxide (10 mg/kg) or saline. The drug significantly enhanced locomotor activity as well as the frequency of Fighting Episodes and of Attacks, while decreasing the number of Submissive Postures and the time spent On Nest. These effects were not significantly modified by prenatal oxazepam exposure. This suggests that long-term and acute effects of benzodiazepines are produced either by changes in different regulatory systems or by different types of changes in the same system.

[Perioperative subjective emotional state]

The aim of adequate preoperative medication is to minimize the patient's anxiety level. Preoperative anxiety can be consciously and specifically orientated or it can be masked. This double-blind study was performed to evaluate the effects of an anxiolytic drug in comparison with a placebo perioperatively and to assess the post-operative course of the important factors anxiety, depression and asthenia. The Mannheim inventory for subjective state and STAI (State-Trait-Anxiety-Inventory) were offered. The study was undertaken in 60 female patients, who were operated for suspected carcinoma of the breast. We conclude that in such a specific group of patients extensive preoperative psychological preparation must be backed up by the administration of an anxiolytic drug.

A double-blind, controlled trial in primary care patients with generalized anxiety: a comparison between buspirone and oxazepam

Two hundred thirty patients with generalized anxiety and Hamilton Rating Scale for Anxiety (HAM-A) scores greater than or equal to 18 were subdivided at random, according to a double-blind design, into one group treated with 5-10 mg of oral buspirone t.i.d. or one group treated with 10-20 mg of oral oxazepam t.i.d. for 6 weeks. No anxiolytic treatment was allowed 3 months prior to trial entry. Analysis of demographic variables revealed no significant imbalance between the two treatment groups. Twenty patients were excluded from efficacy analysis because of treatment withdrawal before the first efficacy evaluation on Day 7. Another 4 patients were excluded because they were taking concomitant psychotropic medication. The remaining 206 patients displayed a decrease in HAM-A scores (mean +/- SD) from 23.9 +/- 4.1 to 10.6 +/- 7.7 in the buspirone group and from 23.9 +/- 4.2 to 11.5 +/- 8.0 in the oxazepam group. The two treatment groups were also found to be virtually identical in an "intent to treat" analysis of all 230 patients as well as in other ratings (Hamilton Rating Scale for Depression, Raskin Depression Scale, Covi Anxiety Scale, Physicians Questionnaire, global ratings, and Hopkins Symptom Checklist [HSCL]-56). However, oxazepam was never superior to buspirone in any of the efficacy analyses. Of the 230 patients, 127 spontaneously reported adverse events, including drowsiness, dizziness, headache, nausea, and nervousness. Adverse events were relatively similar in the two groups. In conclusion, buspirone and oxazepam appear to be equally effective in the treatment of generalized anxiety encountered by general practitioners. This outcome, in addition to a previously documented absence of any dependency liability, makes buspirone a clinically important anxiolytic drug.

The effects of flumazenil-precipitated abstinence on the pharmacokinetics of chronic oxazepam in dogs

The pharmacokinetics of oxazepam was studied in naive dogs and in oxazepam-dependent dogs without and with administered flumazenil (6 mg/kg). Oxazepam is eliminated with a relatively short elimination half life (ca. 150 min) in both acutely and chronically treated dogs. It exhibits only a modest first pass metabolism (ca. 10%) and its bioavailability following oral administration is about 22%. The steady state concentration of oxazepam in chronically treated dogs was lower than was predicted from single dose studies. Flumazenil did not change the rate of absorption or elimination of oxazepam-dependent dogs. The total steady state plasma concentration of oxazepam was significantly reduced by flumazenil administration suggesting a displacement interaction between flumazenil and oxazepam.

Comparative effectiveness and costs of inpatient and outpatient detoxification of patients with mild-to-moderate alcohol withdrawal syndrome

We compared the effectiveness, safety, and costs of outpatient (n = 87) and inpatient (n = 77) detoxification from alcohol in a randomized, prospective trial involving 164 male veterans of low socioeconomic status. The outpatients were evaluated medically and psychiatrically and then were prescribed decreasing doses of oxazepam on the basis of daily clinic visits. The inpatient program combined comprehensive psychiatric and medical evaluation, detoxification with oxazepam, and the initiation of rehabilitation treatment. The mean duration of treatment was significantly shorter for outpatients (6.5 days) than for inpatients (9.2 days). On the other hand, significantly more inpatients (95 percent) than outpatient (72 percent) completed detoxification. There were no serious medical complications in either group. Outcome evaluations completed at one and six months for 93 and 85 percent of the patients, respectively, showed substantial improvement in both groups at both follow-up periods. At one month there were fewer alcohol-related problems among inpatients and fewer medical problems among outpatients. However, no group differences were found at the six-month follow-up, nor were differences found in the subsequent use of other alcoholism-treatment services. Costs were substantially greater for inpatients ($3,319 to $3,665 per patient) than for outpatients ($175 to $388). We conclude that outpatient medical detoxification is an effective, safe, and low-cost treatment for patients with mid-to-moderate symptoms of alcohol withdrawal.

The use of benzodiazepine hypnotics in the elderly

An epidemiologic study was conducted to observe patient-reported use and effects of triazolam, flurazepam, and oxazepam taken at bedtime among 2260 outpatients age 65 years or older in Canada. The study used pharmacy-based enrollment, with participant follow-up through a 3-day diary and a telephone interview. The study also evaluated how the three benzodiazepine hypnotics were prescribed. Prescription information showed that 66% of the flurazepam prescriptions were for the highest strength, compared to 39% and 35% for triazolam and oxazepam, respectively. As patient age increased, the highest strength of each agent was prescribed less frequently. For all drugs, 53% of prescriptions were written for use as necessary (prn), and the proportion who received such prescriptions increased with age. Patient reports, however, revealed that 57% were using a hypnotic every day, and this regular use increased with advancing age. Regular daily use was more common among those who used triazolam and oxazepam (62%) than those who took flurazepam (42%).

[Drug interaction between imipramine hydrochloride and benzodiazepines when administered orally for 15 days]

The effects of daily oral administration of imipramine (IM) hydrochloride (50 mg/kg) and/or oxazepam (OZ, 20 mg/kg) or diazepam (DZ, 5 mg/kg) in a 1% aqueous solution of carboxymethylcellulose sodium salt (CMC) on the activities of drug metabolizing enzyme systems and steady state plasma levels of IM, desmethylimipramine (DIM), DZ, desmethyl-diazepam (DDZ) and OZ were investigated in rats during a 15-day period. In addition, the effect of a single intravenous administration of IM hydrochloride (5 mg/kg), DZ (0.5 mg/kg) and OZ (2 mg/kg) on plasma concentration-time profiles of IM, DIM, DZ, DDZ and OZ was investigated in rats given the same drug treatments by the oral route for 14 days. The group treated with IM hydrochloride plus OZ group showed a great increase in drug-metabolizing enzyme activities, but the difference for the group given IM hydrochloride was not statistically significant. The steady-state plasma levels of DZ after oral administration for 15 days suggested that the group given IM hydrochloride plus DZ did show accumulated DZ. In terms of the area under the concentration-time curve of IM, DZ and OZ after intravenous administration of IM hydrochloride, DZ and OZ, there were significant differences between each of the mono-treatment groups and the IM hydrochloride plus DZ or OZ treatment groups. In conclusion, we have found that the drug interaction for IM hydrochloride by OZ is markedly lower than that by DZ.

Bioavailability and pharmacokinetics of oxazepam

Six healthy volunteers received oxazepam 15 mg i.v. and orally at an interval of at least one week. The kinetic variables of i.v. oxazepam were: elimination half-life (t1/2 beta) 6.7 h, total clearance (CL) 1.07 ml.min-1.kg-1, volume of distribution (Vc) 0.27 l.kg-1 (0.21-0.49) and volume of distribution at steady-state (Vss) 0.59 l.kg-1. The intravenous disposition of unbound oxazepam was characterized by a clearance of 22.5 ml.min-1.kg-1 and a distribution volume of 12.3 l.kg-1. After oral oxazepam the peak plasma level was reached in 1.7 to 2.8 h. The plasma t1/2 beta at 5.8 h was not significantly different from the i.v. value. Absorption was almost complete, with a bioavailability of 92.8%. Urinary recovery was 80.0 and 71.4% of the dose after intravenous and oral administration, respectively. Renal clearance (CLR) of the glucuronide metabolite was 1.10 ml.min-1.kg-1 (0.98-1.52). Oxazepam was extensively bound to plasma protein with a free fraction of 4.5%.

Pentobarbital-like discriminative stimulus properties of halothane, 1,1,1-trichloroethane, isoamyl nitrite, flurothyl and oxazepam in mice

Volatile inhalants represent a diverse group of chemicals which pose a public health problem because of their abuse potential and neurobehavioral toxicity. Although relatively little is known about their pharmacology, they share certain pharmacological properties with classic central nervous system depressants. Drug discrimination procedures were used to compare the effects produced by pentobarbital (PB), oxazepam and several inhalants. Mice were trained to discriminate PB from saline injections in a two-lever operant task. Stimulus generalization was examined after 20-min inhalation exposures to halothane (500-8000 ppm), 1,1,1-trichloroethane (500-12000 ppm), isoamyl nitrite (150-1050 ppm), flurothyl (562-1300 ppm) and injections of oxazepam (0.1-20 mg/kg). Halothane, 1,1,1-trichloroethane and oxazepam produced discriminative stimulus effects similar to those produced by PB. Isoamyl nitrite and flurothyl, while decreasing rates of responding, were not consistently generalized from PB. Differences are apparent in the PB-like discriminative effects of inhalants. Toluene, as shown in a previous study, as well as halothane and 1,1,1-trichloroethane have PB-like discriminative effects which are also shared by oxazepam and may be another common effect of central nervous system depressants. Other chemicals, like isoamyl nitrite and flurothyl, are representative of qualitatively different classes of behaviorally active inhalants.

Kinetics and dynamics of single doses of oxazepam in the elderly: implications of absorption rate

Five healthy elderly volunteers aged 64 to 67 years and 12 healthy young subjects aged 23 to 44 years received single 30 mg oral doses of oxazepam in two different dosage forms (two 15 mg tablets or one 30 mg capsule) on two occasions in a random crossover sequence, with at least 1 week elapsing between trials. In both age groups, rate of oxazepam absorption of the capsule form of the drug was significantly slower than that of the tablets. Peak plasma concentrations were lower and were delayed longer with the capsule form; however, the relative extent of oxazepam absorption did not differ between preparations in either age group. Clinical self-ratings in the elderly group, based on visual analog scales, were consistent with the delayed onset of sedative effects that is associated with the capsule form of administration. Kinetic comparisons in the two groups indicated a significantly prolonged oxazepam elimination half-life with the tablet (p less than .001) and with the capsule (p less than .06) and a trend (p less than .08) toward reduced oxazepam clearance in the elderly. The delayed absorption of oxazepam from the capsule was found in both the young and elderly groups.

Disposition of oxazepam in patients on maintenance hemodialysis

The pharmacokinetics of a single 30-mg oral dose of oxazepam was evaluated in seven patients with chronic renal failure on maintenance hemodialysis and in seven healthy controls matched for age and sex. Based on total (free plus bound) serum oxazepam concentrations, elimination half-life was prolonged in renal patients compared to controls (22 vs 8 h, p less than 0.001) and volume of distribution increased (3.0 vs 1.4 1/kg, p less than 0.02). However, total clearance was similar between groups (1.8 vs 1.9 ml/min per kilogram). These findings were confounded by the increased oxazepam free fraction in serum of renal failure patients (10.3%) as compared to healthy controls (4.3%). Correction for differences in binding indicates similar distribution of unbound oxazepam between groups, but reduced clearance of pharmacologically active unbound oxazepam in renal patients (18 vs 45 ml/min per kilogram). Oxazepam dosage, therefore, may require downward adjustment for renal failure patients on hemodialysis.