Diazepam actions and plasma concentrations following ethanol ingestion

Superadditive effects of ethanol and flunitrazepam: implications of using immunopharmacotherapy as a therapeutic

While benzodiazepine intoxication alone may elicit sedative and antianxiety effects, alcohol coingestion greatly amplifies this central nervous system depression. As a result, this drug combination gained notoriety for its role in cases of facilitated sexual assault and fatal overdose. We previously validated the ability of the novel antiflunitrazepam monoclonal antibody (mAb) RCA3A3 to bind flunitrazepam (FLU) in vivo and block FLU-induced impairment of locomotion and memory. A therapeutically relevant application of this high affinity mAb (K(d,app) = 200 nM), however, is to the more tenuous indication of flunitrazepam (FLU) and alcohol cointoxication. Employing a murine behavioral model, passive immunization with mAb RCA3A3 before injection of ethanol (EtOH: low-dose, 1 g/kg, or high-dose, 1.5 g/kg), FLU (0.06 mg/kg), or a cocktail of both drugs offered partial to full restoration of motor activity levels in co-drug treated and FLU-treated mouse groups (n = 12), respectively. Whereas all drug treatments left contextual learning intact, auditory cued learning was severely disrupted. Prophylactic administration of mAb RCA3A3 prevented this deficit in cued learning in FLU-treated mice but not in the FLU- and EtOH-treated mice, in which co-drug exposure exacerbated the impairment in cued fear conditioning. To substantiate this finding, a dose-response study was performed, and the changes in locomotor activity incurred by different FLU (low-dose, 0.06 mg/kg, or high-dose, 0.09 mg/kg), EtOH (1.0 g/kg, 1.5 g/kg), and mAb RCA3A3 (14.5 mg/kg, 21.8 mg/kg) dose combinations illustrated the potentiation in motor effects by concomitant exposure to FLU and EtOH. Thus, motor activity and fear conditioning results demonstrated that both the amount of FLU left unbound by antibody and the pharmacological additivity between FLU and EtOH, a GABA mimetic, were limiting factors in the therapeutic efficacy of mAb RCA3A3. In sum, our study highlights the complex nature of psychomotor impairment upon co-drug versus singular drug exposure, which may pose a unique challenge to therapeutic treatment.

Rotarod studies in the rat of the GABAA receptor agonist gaboxadol: lack of ethanol potentiation and benzodiazepine cross-tolerance

All benzodiazepines and benzodiazepine site agonists impair motor performance dose-dependently and potentiate the effects of ethanol. In order to evaluate the risk of benzodiazepine and ethanol interaction with the direct acting GABA(A) receptor agonist 4,5,6,7-tetrahydroisoxazolo (5,4-c) pyridin-3-ol (gaboxadol), we studied impairment of motor coordination for combinations of gaboxadol, ethanol and a series of benzodiazepines (flunitrazepam, zolpidem and indiplon) in a rat rotarod model. All compounds produced a dose-dependent motor impairment and, in agreement with earlier data, a supra-additive effect of the benzodiazepine ligands and ethanol 1 g/kg was seen. In contrast, no significant potentiation of the effects of gaboxadol by ethanol was detected, and furthermore, no synergistic interaction between gaboxadol and any of the benzodiazepines was seen. A 30-day tolerance study was conducted with daily injections of gaboxadol (7.9 mg/kg) and zolpidem (1.25 mg/kg), respectively. A time-dependent tolerance developed to the motor impairment produced by both compounds. On day 31, cross-tolerance studies between zolpidem/gaboxadol and gaboxadol/zolpidem were conducted. No cross-tolerance was observed, indicating that the motor coordination effects observed with gaboxadol and zolpidem may arise from interaction with different receptor populations.

Profile of acute tolerance to three sedative anxiolytics

Acute tolerance, defined as a decreasing drug effect relative to drug-plasma levels (DPL) over a period of minutes to a few hours, is pronounced following single doses of diazepam or pentobarbital. Both of these lipid-soluble drugs produce an early peak behavioral impairment and subsequent rapid recovery component that is followed by a much slower blood-drug rise time. These pronounced early peak effects were not shared by alcohol, and contribute significantly to the lack of correlation between impairment and DPL.

Benzodiazepine pharmacodynamics: evidence for biophase rate limiting mechanisms

Pharmacokinetics do not adequately reflect recovery from cognitive neuromotor impairment induced by most benzodiazepines. This paper examines across time the nature of the relationship of effect to serum concentration of three benzodiazepines. Using the same protocol lorazepam, alprazolam, diazepam and placebo were administered to eight healthy males at doses of 0.057, 0.029, 0.286 and 0.000 mg/kg, body weight, respectively for the first study and at 0.028, 0.014, 0.143 and 0.000 mg/kg, respectively, for the second study. After each dose administration multiple measurements were made over a period of 5.5-11.5 h using two different psychomotor performance tests. Serum drug concentrations were also measured. The profiles for diazepam and alprazolam effects demonstrate a stepwise decrement in the slopes of the concentration versus response curves across time, illustrating the rapid development of acute tolerance. In contrast, lorazepam induced a remarkably constant relationship between concentration and effect across testing intervals.

Age-related increase in CNS sensitivity to benzodiazepines as assessed by task difficulty

The differential sensitivity of young and elderly healthy adults to the impairment effects of benzodiazepines was assessed by tasks with several levels of difficulty. Using a double-blind procedure, single doses of placebo, alprazolam (0.75 and 1.5 mg) and triazolam (0.25 and 0.5 mg) were ingested orally by 10 young men, 9 young women, 7 elderly men, and 10 elderly women. Order of drug administration was determined by a random Latin square design. Different versions of the subcritical tracking and digit symbol substitution tasks were characterized by three difficulty levels. Assessments of task performance were conducted at varying intervals for 7 h after drug administration. Both drugs induced a rapid initial onset of impairment in the two age groups. Evidence of increased drug sensitivity in the elderly was provided by the more prolonged duration of the pharmacologic effect in the older than young subjects, especially for the harder versions of the SCT and DSS tasks. In summary, the data provide support for the hypothesis of an age-related decline in the adaptive capacity to inhibit adverse drug effects.

Comparative pharmacokinetics and pharmacodynamics of lorazepam, alprazolam and diazepam

The contribution of differential absorption-distribution pharmacokinetics to drug activity can be partially determined by comparing simultaneous estimates of drug serum level with pharmacodynamic effects. In the present paper we have contrasted the effects of clinically equipotent doses of lorazepam, alprazolam, and diazepam on the performance of tracking and digit symbol substitution tasks. Eight young males were tested for 12 h after ingesting the drug. The three benzodiazepines and placebo were administered to each subject according to a balanced double-blind Latin square design. A model is presented that describes the relationship between drug concentration and the degree of impairment across time after the final peak effect. Exponential rate constants were determined for each drug using a Marquardt nonlinear fit of the pooled data. Basically, the constants relate offset serum drug values to the impairment curves at a time when serum-brain equilibrium is assumed to have occurred. The values indicate markedly rapid acute tolerance for alprazolam and diazepam but relatively little acute tolerance for lorazepam. Whether these constants reflect adaptation or differential association-dissociation receptor rate constants cannot be determined, but they do highlight the need to consider receptor kinetics as an important factor in benzodiazepine pharmacodynamics.

Pharmacokinetic-pharmacodynamic modelling of the EEG effects of midazolam in individual rats: influence of rate and route of administration

1. The purpose of the present investigation was to quantify the concentration-pharmacological effect relationship of midazolam in individual rats by use of effect parameters derived from aperiodic EEG analysis. By varying the rate and route of administration the role of (inter)active metabolites and development of acute tolerance was evaluated. 2. The pharmacokinetics and pharmacodynamics of midazolam were determined after intravenous administration of 10 mg kg-1 during 5, 30 and 60 min and oral administration of 15 mg kg-1. Following intravenous administration the pharmacokinetics were most adequately described by a bi-exponential equation. The values (mean +/- s.e. mean, n = 20) of clearance, volume of distribution at steady-state and terminal half-life were 67 +/- 2 ml min-1 kg-1, 1.61 +/- 0.071 kg-1 and 27 +/- 1 min, respectively. Following oral administration midazolam was rapidly absorbed with a systemic availability of 45 +/- 9%. 3. The averaged amplitudes in the 11.5-30 Hz (beta) frequency band of the fronto-central lead on the left-hemisphere, as derived by aperiodic EEG analysis, was selected as a measure of the pharmacological effect of midazolam. By pharmacokinetic-pharmacodynamic modelling the individual concentration-EEG effect relationships of midazolam were derived, which were successfully quantified by the sigmoidal Emax model. No marked and systematic differences in pharmacodynamic parameters were found between the rates and routes of administration. The averaged pharmacodynamic parameters of midazolam obtained after combining the results of all rates and routes of administration were (mean + s.e.mean, n = 27): Eo = 61 + 3puV s 1, Emax = 85 + 3 Vs 1, EC50 = 40 + 3 ngmlP-1 and N = 0.84 + 0.04. 4. The results of the present study show that the concentration-EEG effect relationship of midazolam can be characterized in individual animals using the amplitudes in the 11.5-30 (beta) frequency band as a measure of pharmacological response. Acute tolerance did not develop and (inter)active metabolites did not contribute to this effect parameter within the time span of the experiments.

Comparison of the relationship between structure and CNS effects for lorazepam, clonazepam and alprazolam

Eight healthy young males were administered single doses of lorazepam (4 mg), clonazepam (4 mg), alprazolam (2 mg) or placebo, and their performance on behavioral tasks was monitored for 7 h. Lorazepam and clonazepam impaired performance on subcritical tracking, a primarily neuromotor task, for 2-4 h longer than alprazolam. Although the duration of impairment of the digit symbol substitution task was less discrepant for the three drugs, clonazepam and lorazepam still affected performance for a longer period of time than alprazolam. The rapid development of acute tolerance was indicated by clockwise hysteresis curves for all the drugs on the SCT task and for clonazepam and alprazolam on the DSS task. The maximum effect, effect offset rate and duration of the drug effect are discussed in relation to molecular structure and receptor affinity.

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.

Effects of single doses of alprazolam and diazepam, alone and in combination with ethanol, on psychomotor and cognitive performance and on autonomic nervous system reactivity in healthy volunteers

Effects of alprazolam, alone and in combination with ethanol, on psychomotor and cognitive performance were studied in healthy male volunteers and compared to effects of diazepam. Alprazolam 2 mg produced relatively long-lasting impairments on tests of tracking, verbal and nonverbal information processing, and memory, and decreased blood pressure without a change in heart rate or plasma norepinephrine levels. Although ethanol consumption was demonstrated to produce additive decrements in performance on certain tasks, there was little evidence to support a synergistic effect. Alprazolam 2 mg was accompanied by increased self-reports of side effects, especially drowsiness. Low dose alprazolam, diazepam, and ethanol produced significantly fewer side effects than 2 mg alprazolam, but significantly more than placebo.

Positive interaction of ethanol and kava resin in mice

1. The lipid soluble extract of the psychoactive beverage kava has hypnosedative properties which can be measured by the length of time that the righting reflex is lost. 2. Ethanol and the lipid soluble extract (kava resin) have been shown greatly to increase each others hypnotic action in mice. Ethanol also increases the toxicity of kava markedly. 3. This interaction of kava and alcohol has important clinical and social consequences since, in contrast to traditional usage, kava is now often taken in conjunction with alcoholic drinks.

Effects of adinazolam and diazepam, alone and in combination with ethanol, on psychomotor and cognitive performance and on autonomic nervous system reactivity in healthy volunteers

Effects on psychomotor and cognitive performance of adinazolam (15 or 30 mg), alone and in combination with ethanol (0.8 g/kg), were studied in healthy male volunteers and compared to effects of 10 mg diazepam. Adinazolam 30 mg produced relatively long-lasting impairments on tests of tracking, attention, verbal and nonverbal information processing, and memory. Adinazolam 15 mg resulted in descreased visual information processing. Adinazolam decreased supine mean arterial pressure, but only the 15 mg resulted in a tendency for decreased plasma norepinephrine concentrations. After standing for 5 min, 30 mg adinazolam was associated with increased heart rate. Although ethanol consumption produced additive decrements on a continuous performance task, there was little evidence to support a synergistic effect. Adinazolam 30 mg was accompanied by increased self-reports of side effects, especially drowsiness.

Aging: modulation of GABAA binding sites by ethanol and diazepam

Modulation of gamma-aminobutyric acid (GABA) binding to the GABAA recognition site by ethanol and/or diazepam appears to change with the age of the animal. Brain tissue above the cerebellum of young, mature, and old rats was examined for an age-related change in the GABAA recognition sites 5 min after the rat was last habituated or received a single injection of the vehicle, ethanol and/or diazepam. The dose of ethanol injected was reduced in the senescent rats, so the brain levels of ethanol did not vary with age. An injection of ethanol and/or diazepam (180 micrograms/kg) did not significantly alter the GABAA recognition site in any age group relative to the habituated or vehicle-injected rats of that age group. However, the affinity of the GABAA recognition site was decreased by ethanol in mature and old rats relative to the affinity of the GABAA site after diazepam pretreatment in the presence and absence of ethanol, respectively. Finally, the combination of ethanol and diazepam elicited an increase in the number of GABAA binding sites relative to diazepam pretreatment in only the young rats. The present results indicate that the GABAA binding site is modulated by ethanol and diazepam in an age-dependent manner.

Pharmacokinetics and bioavailability of intravenous and oral chlordesmethyldiazepam in humans

Six healthy, fasting volunteers were given single doses of chlordesmethyldiazepam by 1 mg i.v., or as drops or tablets. Chlordesmethyldiazepam and its metabolite, lorazepam, in multiple plasma samples and in urine collected for 120 h after each dose were determined by electron-capture GLC. Mean kinetic variables for intravenous chlordesmethyldiazepam were: volume of distribution, 1.71 l.kg-1; elimination half-life, 113 h; total clearance, 0.21 ml.min-1.kg-1; cumulative excretion of lorazepam glucuronide 24.2% of the dose. Following a lag time of 15.5 min (tablets) and 4.2 min (drops), which were significantly different, the absorption of oral chlordesmethyldiazepam was a first order process, with apparent absorption half-life values averaging 1.5 h (tablets) and 1.1 h (drops). Bioavailability was 77% for tablets and 79% for drops.

Benzodiazepine hypnotic metabolism: drug interactions and clinical implications

Benzodiazepines are the drugs of choice when initiating hypnotic therapy. Though the mechanism of benzodiazepine action in the central nervous system is similar for all drugs in this class, differences in absorption and pathway of elimination are associated with differences in observed clinical effect. After single-dose administration, onset of hypnotic effect is most closely related to rate of drug absorption and duration of effect is more closely associated with extent of drug distribution. Relative affinity of the individual benzodiazepine for the specific central nervous system binding site may also determine duration of action. During multiple-dose chronic therapy, route of metabolic biotransformation and elimination half-life assume more importance. An increased incidence of adverse drug effects due to high doses of accumulating benzodiazepines may be seen in the elderly and patients with central nervous system deficits or chronic liver disease. Benzodiazepine metabolic biotransformation and clearance is broken into three groups. Group 1--oxidative biotransformation; Group 2--high clearance drugs; Group 3--drug conjugation. Groups 1 and 2 are implicated in a number of drug-disease and drug-drug interactions. Group 3 drugs have little change in patients with liver disease or when administered with inhibitors of drug biotransformation. Clinical implications of these metabolic interactions are variable, but inhibition of Group 1 and 2 benzodiazepine clearance has been associated with increased sedation and psychomotor impairment.

Reinterpretation of the pharmacokinetic mechanism of oral benzodiazepine ethanol interaction

Previously published studies investigating the oral benzodiazepine ethanol interaction have utilized a single dose of ethanol, a single dose of oral benzodiazepine, and measured plasma benzodiazepine concentration over varying time periods. Most studies reported an increase or no change in benzodiazepine plasma concentrations following ethanol administration, which the investigators usually ascribed to an ethanol-induced increase in the benzodiazepine absorption rate constant. However, ethanol decreases the hepatic clearance of benzodiazepines that are biotransformed via the P450 enzyme system and this effect was not taken into account in evaluation of the results of these studies. Computer simulations have been used to investigate possible mechanisms of the oral benzodiazepine-ethanol interaction. The effects of a constant or transient decrease in clearance and an increase in absorption rate constant upon maximum concentration, time of maximum concentration, and area under the benzodiazepine plasma concentration curve (AUC) have been examined. A transient 75% decrease in benzodiazepine clearance resulted in a 13.6% increase in AUC (0-36 hr), a 3.4% increase in Cmax and a 5.7% increase in tmax. These changes are qualitatively consistent with, but quantitatively shy, of those observed in most studies. Consequently, an effect of ethanol upon benzodiazepine absorption must still be considered.

Ethanol drug interaction with chlordiazepoxide and pentobarbital

Drug interactions between ethanol and pentobarbital and ethanol and chlordiazepoxide were investigated utilizing mice. At the peak of oral ethanol (0-4 g/kg), either sodium pentobarbital (1-120 mg/kg) or chlordiazepoxide hydrochloride (2-400 mg/kg) was given intraperitoneally. Blood concentrations of ethanol, pentobarbital, chlordiazepoxide, and its pharmacologically active major metabolites were monitored utilizing either gas chromatography or high performance liquid chromatography. Lethality and loss-of-righting reflex were measured as indexes of behavioral drug interactions. It was evident from the isobolographic plot that the interactions between ethanol and pentobarbital and ethanol and chlordiazepoxide were more than additive. Interaction between ethanol and pentobarbital was greater than that between ethanol and chlordiazepoxide. Furthermore, with increasing ethanol pretreatment the shift in dose-response curves for the loss-of-righting reflex was affected more than the shift in dose-response curves for lethality. Blood concentration monitoring of each drug indicated that the rate of biotransformation of pentobarbital was significantly decreased; sequential biotransformation of chlordiazepoxide was also altered, resulting in a large accumulation of demethylchlordiazepoxide in the blood.

Effects of ethanol on drug and metabolite pharmacokinetics

Pharmacokinetic interactions of ethanol with other drugs, including its effects upon drug metabolite disposition, are reviewed in terms of clearance concepts. This approach is particularly useful in understanding the mechanisms of ethanol-drug interactions, i.e. in separating the effects of ethanol upon drug clearance, volume of distribution and plasma protein binding. The application of clearance concepts provides the basis for understanding the qualitative differences in ethanol interactions with low and high hepatic extraction ratio drugs. The effects of short and long term ethanol consumption upon different types of drug metabolism (oxidative, acetylation and glucuronidation) have been considered. Long term ethanol consumption may increase the clearance of a drug by induction of oxidative metabolism whereas short term consumption may decrease the clearance of such a drug. Clearance by N-acetylation appears to be increased in the presence of ethanol, and clearance by conjugation to glucuronic acid is decreased for some drugs by single-dose consumption of ethanol.

Behavioral effects of oral versus intravenous administration of diazepam

The behavioral effects of oral versus intravenous administration of diazepam were studied in 50 volunteers using a battery of memory, cognitive, mood and psychomotor tests repeated over a 4.5 hr period. Subjects received diazepam 0.2 mg/kg or placebo as capsules, commercial tablets or intravenous solution in a randomized double blind manner. While a quick onset of effects occurred with intravenous administration followed by the capsule and tablet oral administrations in that order, the recovery rate was similar for the 3 methods of administration. Contrary to many claims in the literature the effects of oral administration were substantial. Behavioral impairment was directly related to the magnitude of the memory component of the task. On many of the tasks the pattern of diazepam impairment was one of delayed improvement of performance, a pattern which would only be apparent with repeated testing. Subjects who received diazepam showed a paradoxical enhancement of recall for material learned before the drug.

Benzodiazepine drug-drug interactions commonly occurring in clinical practice

Pharmacokinetic drug-drug interactions which involve currently available benzodiazepines may be classified into two major categories: interactions which affect benzodiazepine rate of absorption, and interactions which affect clearance and, therefore, elimination half-life. Ethanol is the prototype for absorptive interactions. Concurrent ethanol use and oral ingestion of benzodiazepine derivatives uniformly slows the rate but does not change the extent of benzodiazepine absorption. Interactions which affect benzodiazepine clearance affect only those derivatives which are oxidatively metabolized or cleared as a function of hepatic blood flow (high first-pass clearance). Conjugated benzodiazepines are not implicated in such interactions. Rifampin and chronic ethanol use induce benzodiazepine oxidation, while cimetidine, oral contraceptives, ethanol (acute ingestion), disulfiram, isoniazid, and propranolol inhibit benzodiazepine oxidation. In addition, ethanol, cimetidine and isoniazid decrease first-pass hepatic extraction of triazolam, enhancing its systemic availability and decreasing oral clearance. The pharmacokinetic consequence of induction of benzodiazepine oxidation is higher clearance and decreased steady-state concentrations during chronic dosing. Conversely, inhibition of benzodiazepine oxidation decreases clearance and increases steady-state benzodiazepine concentrations during chronic dosing. Because a correlation of benzodiazepine plasma concentration and pharmacological effect is not established, the pharmacodynamic consequences of these interactions are not currently well characterized.

Plasma concentrations of benzodiazepines--a review of clinical findings and implications

Methods for benzodiazepine analysis are briefly discussed and the pharmacokinetics of the benzodiazepines reviewed. Studies of the relationship between plasma concentration and anxiolytic response have produced conflicting results. Routine monitoring in anxiety states is not warranted. Some specific indications for monitoring are in elderly patients; in cases of suspected non-compliance; in patients with renal and hepatic disease. The relationship between plasma concentration and ECG changes following benzodiazepine overdose showed that monitoring was of little value in these cases.

Alcohol and bupropion pharmacokinetics in healthy male volunteers

A study was performed to determine whether there is a pharmacokinetic interaction between alcohol and the novel antidepressant bupropion. In the first part 8 healthy male volunteers received single doses of 100 mg bupropion hydrochloride orally on 2 occasions accompanied by either ethanol in orange or plain orange drink according to a balanced cross over design. Plasma bupropion concentrations were determined by radioimmunoassay and kinetics analysed with the aid of NONLIN. Blood alcohol levels were assessed by breathalyser. The disposition of bupropion was adequately described by a 2 compartment model and kinetic parameters were not significantly altered by the presence of alcohol. In the second part of the study the same subjects received 40 ml ethanol in orange drink 3.5 h after ingestion of 100 mg bupropion or dummy tablet in a double blind cross over fashion. Bupropion did not affect alcohol kinetics. In contrast to many other psychotropic drugs there is no evidence for a kinetic interaction between bupropion and alcohol.

Interactions of benzodiazepines on psychomotor skills

Interactions of centrally active drugs are difficult to analyse in man due to methodological and ethical problems. Alcoholic and methylxanthine beverages are the most common centrally active agents that might modify the effects of benzodiazepines on performance. In sufficiently large doses ethanol enhances the effects of benzodiazepines, even those that are not metabolized by mixed function oxidases sensitive to blockade by ethanol. Consequently, the combined effect of ethanol and benzodiazepines may occur at the receptor level and/or result from altered binding of benzodiazepines to plasma proteins. Newer benzodiazepines may differ from the older in their interactions. Caffeine and theophylline counteract benzodiazepine effects on performance, resulting perhaps from the blockade of adenosine receptors which could be linked with the GABA-benzodiazepine receptor system. Central stimulants of the amphetamine type also counteract benzodiazepine effects in a somewhat selective way. New stimulant antidepressants rather counteract than increase benzodiazepine effects. Central antimuscarinics in combination with benzodiazepines are detrimental for memory. Specific benzodiazepine antagonists are effective also in man but without known clinical applications.

Interaction of the discriminative stimulus properties of diazepam and ethanol in pigeons

One group of pigeons (n = 5) was trained to discriminate between the effects induced by 5.6 mg/kg of diazepam (DZP) and the vehicle whereas other pigeons (n = 5) had to discriminate between 3.0 g/kg of ethanol (ETOH) and the vehicle, administered intragastrically (IG) 10 and 40 min prior to the training sessions respectively. Once trained, the pigeons were tested with either diazepam or ethanol alone and in combination. The birds trained to discriminate between DZP and the vehicle mostly performed non-drug associated responses when tested with ETOH (0.56 to 3.0 g/kg). Tests with other doses of DZP (0.3 to 3.0 mg/kg) in the diazepam-trained birds resulted in an ED50 value of 1.4 mg/kg. The birds trained to discriminate between ETOH and the vehicle generalized DZP to ETOH, the ED50 value for diazepam being 3.0 mg/kg. Tests with other doses of ETOH (0.56 to 2.0 g/kg) in this latter group resulted in an ED50 value of 1.3 g/kg. Tests with combinations of DZP and ETOH produced a shift of the dose-response curves to the left indicating drug additivity. The discrimination of 5.6 mg/kg of IG administered DZP but not that of ETOH (3.0 g/kg) was attenuated by injections of the analeptic bemegride (ED50 = 5.5 mg/kg), thus suggesting a difference in the cueing processes of the two drugs. When tested singly, bemegride induced non-drug responding or complete suppression of responding in the birds at the doses of 3.0 and 10.0 mg/kg respectively. In conclusion, the discriminable effects of DZP and ETOH are additive or even supra-additive, but the stimulus properties of the two drugs are not identical.

Influence of alcohol on the pharmacokinetics of diazepam controlled-release formulation in healthy volunteers

Twelve normal volunteers were empanelled in an open-label, three-way crossover study to evaluate the influence of alcohol on the pharmacokinetics of controlled-release diazepam capsules. Each volunteer received one 15-mg diazepam controlled-release capsule alone, concomitantly with alcohol or followed by alcohol 2 hours later. The mean plasma concentration-time profiles following both alcohol treatments were superimposable on the profile from the control. The mean plateau concentrations were observed to endure from 2 through 12 hours in all cases. The mean +/- S.D. areas under the plasma concentration-time curves from time zero to infinity were similar indicating no difference in the extent of absorption of diazepam in the presence of alcohol. The harmonic mean elimination half-lives were also similar. Overall, the pharmacokinetics and the release properties of controlled-release diazepam capsule were not influenced by alcohol in normal volunteers.

Actions and interactions of diazepam and alcohol on psychomotor skills in young and middle-aged subjects

Healthy pretrained men participated in three separate controlled double-blind and cross-over trials. There were 10 students in Trial I, 11 army officials or policemen aged 38-59 years in Trial II, and 11 students in Trial III. After single oral doses of diazepam 10 mg (D), placebo, alcohol 0.5 g/kg (A) or D+A, given at one-week intervals in balanced order, the psychomotor skills (choice reaction, tracking, attention, flicker fusion) were repetitively measured up to 2.5 hrs. Serum D concentrations were measured by gas chromatography. D alone impaired flicker fusion in trials I and II, and also reactive and coordinative skills in trial III. A alone slightly impaired skills and failed to potentiate D effects. Increasing age rendered the performance worse but this was due to increased base-line errors rather than to enhanced responses to D. Serum D concentrations tended to rise in the presence of A suggesting an inhibition of D demethylation by alcohol. Both total and free concentrations of D were similar in both age groups. The results suggest that in spite of unaltered sensitivity to D, middle-aged subjects have a lowered margin of safety when driving or using machinery under D treatment.

Effects of amitriptyline and zimelidine in combination with ethanol

Six healthy male volunteers took part in this three-period crossover study. In each session, a dose of trial drug -- either placebo, zimelidine 200 mg, or amitriptyline 75 mg -- was given at 09.00 h. Ethanol (50 g) was taken orally at 1200 h. Blood samples were taken for measurement of drug and ethanol concentrations, and body sway and subjective sedation were determined. No differences in the pharmacokinetics of ethanol were seen between the three treatment sessions. Amitriptyline and ethanol showed marked sedative effects, and the results suggest that these two effects may be additive. The combination of amitriptyline and ethanol results in a particularly marked increase in body sway. No sedative nor alerting effect of zimelidine was seen, nor was any interaction between zimelidine and ethanol apparent.

Factors influencing the activity and fate of benzodiazepines in the body

1 The clinical pharmacokinetics of the many benzodiazepines used to treat numerous and varied clinical conditions can be influenced by many factors. 2 Combinations of drugs efficacious in the central nervous system can change the onset, intensity and duration of effect as a result of pharmacological, physiological and pharmacokinetic actions. 3 Pharmacokinetic considerations indicate that short to medium long-acting benzodiazepines that depend on only glucuronidation for their major metabolic pathway are the drugs of choice in this category.

Short-term ethanol administration impairs the elimination of chlordiazepoxide (Librium) in man

Ethanol may enhance the sedative effect of benzodiazepines leading to greater psychomotor impairment, but the mechanism is not clear. The present study was carried out to determine the effect of acute ethanol ingestion on the disposition and elimination of chlordiazepoxide (Librium), a widely used benzodiazepine. Five healthy, 22-39-year-old, male volunteers ingested ethanol 0.8 g/kg as 25% in orange juice 1 h before chlordiazepoxide 0.6 mg/kg was injected intravenously. To maintain plasma ethanol concentrations of 50-150 mg!100 ml for 32 h additional ethanol 0.5 g/kg was given orally every 5 h. Plasma clearance of chlordiazepoxide fell from 26.6 +/- 2.6 ml/min (mean +/- SD) without ethanol to 16.6 +/- 3.1 ml/min (P less than 0.05) after ethanol. There was no change in the volume of distribution and therefore the elimination half-life was prolonged from 7.1 +/- 1.9 h to 11.8 +/- 6.0 h (P less than 0.05) after ethanol. Ethanol also lowered the plasma binding of chlordiazepoxide from 94.7 +/- 0.6% to 93.4 +/- 1.3% (P less than 0.05). The plasma clearance of unbound chlordiazepoxide fell from 468 +/- 51 ml/min to 264 +/- 98 ml/min (P less than 0.05) after ethanol. The plasma level of the metabolite desmethylchlordiazepoxide was higher and its elimination slower after ethanol. Thus using a pharmacokinetic approach this study has demonstrated that short-term ethanol ingestion in moderate doses impairs the elimination of chlordiazepoxide and accounts, at least partly, for the greater sedation that results when ethanol is taken concomitantly.

Diurnal variations in plasma diazepam concentrations associated with reciprocal changes in free fraction

1 The characteristics and mechanism of fluctuations in diazepam and N-desmethyldiazepam concentrations and diazepam free fraction were studied in six volunteers, who received diazepam (10 mg, i.v. over 20 min) and in five chronic diazepam users. 2 Within a day total diazepam and N-desmethyldiazepam concentrations varied significantly (P less than 0.001) and were lower than predicted between 23.00 and 08.00 h and higher by 09.00 h. In contrast, diazepam free fraction also varied significantly (P less than 0.001) and was highest between 23.00 and 08.00 h and lower by 09.00 h. Coincident increases in total diazepam concentrations (P less than 0.005) and decreases in diazepam free fraction were associated with food intake (P less than 0.05). 3 The coincident diurnal variations in diazepam and N-desmethyldiazepam concentrations and the negative correlation between total diazepam concentration and diazepam free fraction (r = 0.73, P less than 0.001) suggest that the mechanism of the fluctuations is intravascular and tissue redistribution rather than effect on drug biotransformation. 4 These variations may introduce large between and within investigator experimental differences in the determination of kinetic parameters. Free drug concentration varies over the day, and within day variations in clinical effect may be observed.

Tofisopam, a novel 3,4-benzodiazepine: multiple-dose effects on psychomotor skills and memory. Comparison with diazepam and interactions with ethanol

Twelve healthy male volunteers were treated (double-blind crossover design) with tofisopam (a new 3,4-benzodiazepine), diazepam, or placebo, on 2 consecutive days each. Psychomotor skills were impaired after a single dose of diazepam (10 mg) given on day 1. Measurements on day 2 showed that some tolerance had developed to the diazepam-induced impairment of reactive and coordinative skills, but not to its effects on flicker fusion or on the extraocular muscle balance. Tofisopam failed to impair performance both as a single dose (100 mg) and after repeated doses (100 + 50 + 50 + 100 mg). The subjects felt more fatigue, dizziness, calmness, and passiveness after diazepam than after tofisopam. When either drug was given together with 0.8 g/kg ethanol on day 2, the breath ethanol concentrations were 0.7--1.0 mg/ml and all psychomotor skills were impaired. Diazepam + ethanol particularly impaired memory and learning as well. After this combination the subjects were classified (time anticipation test) as 'disqualified drivers' more often than after placebo. It is concluded that diazepam, as well as either benzodiazepine with ethanol, may reduce the ability to drive vehicles or operate machinery.

Acute and subacute effects of diazepam on psychomotor skills: interaction with alcohol

Effects of diazepam and alcohol on psychomotor skills were measured in two trials. In the first one, 200 healthy students volunteered for a double-blind single-dose study. Three doses of diazepam (5, 10 and 20 mg) and alcohol (0.5, 0.8 and 1.2 g/kg) were used alone and combined to construct dose-response graphs. All doses of alcohol impaired divided attention while co-ordinative skills were impaired by the 1.2 g/kg dose. Diazepam alone did not impair reactive or co-ordinative skills whereas the combinations of diazepam and alcohol did so. To further elucidate the subactue effects, a double-blind randomized study was conducted administering 2 and 10 mg of diazepam t.i.d. for two weeks to 18 healthy volunteers. The psychomotor tests were performed on the 7th and 14th days of drug administration, and 0.5 g/kg of alcohol was given on either day. Diazepam 2 mg, alone or with alcohol, did not differ from placebo. 10 mg of diazepam slightly increased reaction times but not reaction mistakes, and impaired both co-ordination and attention. Alcohol did not enhance diazepam effects. We suggest that a development of tolerance to diazepam may compensate the deleterious interaction of the agents found in acute studies.

Self-rated sedation and plasma concentrations of desmethyldiazepam following single doses of clorazepate

Plasma concentrations of desmethyldiazepam (DMDZ) and intensity of self-rated sedation (SRS) were measured at multiple points in time during 6 h after a single 15 mg oral dose of clorazepate dipotassium. Mean plasma DMDZ levels and mean SRS scores both became maximal at 1.0--2.5 h after drug dosage. By 6 h, however, mean SRS had returned to the predrug baseline score while mean DMDZ concentration fell only slighty from the maximum value. Disappearance of SRS despite persistence of high DMDZ levels might be due to adaptation or tolerance. If this is the case, subjective effects of benzodiazepines may depend upon duration of drug exposure as well as dose and concentration.