The role of cytochrome P450 2C19 activity in flunitrazepam metabolism in vivo

Flunitrazepam, a hypnotic benzodiazepine, is widely prescribed around the world for the treatment of insomnia and as a preanesthetic. In vitro studies have shown that the metabolism of flunitrazepam to desmethylflunitrazepam and 3-hydroxyflunitrazepam is mediated in part by the polymorphic enzyme CYP2C19. The objective was to examine the role of CYP2C19 activity in determining flunitrazepam kinetics in vivo. Sixteen healthy volunteers (14 genotypic extensive metabolizers and 2 poor metabolizers) were recruited who had a wide range of CYP2C19 activity (0.50-28.8), as determined by the omeprazole/ 5-hydroxyomeprazole ratio (OMR) at 3 hours following administration of omeprazole, 20 mg orally. Each subject received flunitrazepam, 1 mg orally. Blood samples were collected immediately before and up to 48 hours after drug administration and were assayed by HPLC for flunitrazepam and its metabolites, 7-aminoflunitrazepam, desmethylflunitrazepam, and 3-hydroxyflunitrazepam. Spearman correlations were determined for OMR and pharmacokinetic parameters. With increasing OMR (decreasing CYP2C19 activity), the ratio of flunitrazepam to both desmethylflunitrazepam and 3-hydroxyflunitrazepam AUCs increased ( r = 0.55, p = 0.03 and r = 0.65, p = 0.01, respectively). However, variation in CYP2C19 activity did not significantly affect the AUCs of flunitrazepam or its metabolites. The authors conclude that CYP2C19 contributes to the metabolism of flunitrazepam to desmethylflunitrazepam and 3-hydroxyflunitrazepam in vivo, but these data suggest that its role is minor and that differences in CYP2C19 activity do not likely substantially influence its clinical effects.

A comparative pharmacokinetic and dynamic evaluation of alprazolam sustained-release, bromazepam, and lorazepam

Sustained-release (SR) alprazolam may facilitate compliance with oral benzodiazepine treatment of panic disorders that currently requires doses administered three or four times daily. To compare the pharmacokinetic, psychomotor performance, and subjective effects of alprazolam SR (1.5 mg), bromazepam (3 mg taken three times daily), and lorazepam (1 mg taken three times daily), 13 male volunteers (aged 20-45 years) randomly received on four separate occasions one of these medications or placebo. Once before and 11 times after drug administration, the subjects were tested using psychomotor performance tests (manual tracking and digit-symbol substitution test [DSST]) and computerized questionnaires (such as the Tufts University Benzodiazepine Scale [TUBS], the Addiction Research Center Inventory, and the visual analog scales) to determine the subjective effects of the drugs. Blood samples for the determination of the plasma levels of the drugs were collected before and 17 times after the drug was administered. A peak plateau of plasma alprazolam began approximately 6 hours after the dose, which was later than the initial peaks for lorazepam and bromazepam (1-2 hours after the dose). Once this plateau had begun, alprazolam SR sustained that concentration better than did the other two formulations. Of the 10 measures on which the response averaged for the first 14 hours differed among drugs (p < 0.05), bromazepam differed from placebo on two measures, lorazepam on four (including DSST Performance and TUBS Sedation), and alprazolam SR on nine (including all four affected by lorazepam). Lorazepam and alprazolam, but not bromazepam, produced significantly more sedation than placebo. The doses of the three drugs were not equipotent in sedation and mood effects. None of the drugs tested differed from placebo on measures relevant to abuse liability.

Comparative abuse liability of intravenously administered remifentanil and fentanyl

Remifentanil is a short-acting, esterase-metabolized opioid analgesic. This study compared the abuse liability of remifentanil with that of fentanyl and placebo in a randomized, double-blind, crossover study. Twelve recreational users of opioids received increasing doses of remifentanil (0.6, 1.2, 1.8, 2.4, and 3.0 microg/kg), fentanyl (0.4, 0.8, 1.3, 2.0, 3.0, and 4.5 microg/kg) and placebo via an intravenous infusion pump. Subjective measures (Cole/Addiction Research Center Inventory [ARCI] scales and visual analog scale [VAS] items such as "High" and "Good Effects") and physiologic variables (blood pressure, O2 saturation, pupil diameter) were recorded. For each measure, the differences from baseline were reduced to an area under the response curve (AUC) and a peak, and each subject's response to the maximum tolerable dose for each of the two active drug classes and mean response to several placebo infusions were entered into a 12 x 3 analysis of variance. All differences in drug versus placebo effects were significant. Although a majority of the peak effects that were measurable within 4 minutes after drug infusion reflected greater remifentanil effects, only one, High VAS, was statistically significant. In contrast, observations that could only be made > or = 5 minutes after drug infusion predominantly indicated significantly greater fentanyl peak effects, including High VAS, Liking VAS, Good Effects VAS, and Cole/ARCI Abuse Potential. Fentanyl AUCs were generally significantly larger than the corresponding remifentanil AUCs. A drug abuser seeking longer-lasting drug effects might select fentanyl over remifentanil, but these data do not completely rule out remifentanil abuse by some individuals with access to both the drug and the infusion equipment or by those who prefer briefer, repeated effects.

Efficacy of dexfenfluramine in the treatment of alcohol dependence

BACKGROUND

A substantial body of evidence supports a role for serotonin in modulating alcohol intake, which suggests that this neurotransmitter represents a promising target for pharmacotherapy development for alcohol use disorders. Dexfenfluramine. a serotonin releaser and reuptake inhibitor, decreases alcohol self-administration by rats. Its greater potency and several mechanisms of action suggest it should be more effective in treating alcohol dependence than drugs that only inhibit serotonin reuptake.

METHODS

We conducted an 11 week, randomized, double-blind trial that compared oral placebo and dexfenfluramine 7.5, 15, 22.5, and 30 mg bid in 136 alcohol-dependent patients. A brief behavioral intervention was offered concurrently.

RESULTS

The majority of subjects were male (72%), and the age of the group was 44 +/- 1 years (mean +/- SD). Both placebo- and drug-treated groups significantly reduced alcohol consumption compared with baseline (a 55% decrease in mean drinks per day; p < 0.01), but there were no significant differences between drug and placebo groups or dose effects for most outcome measures.

CONCLUSIONS

Our results with dexfenfluramine are further evidence that serotonergic medications on their own do not significantly reduce alcohol consumption in alcohol-dependent individuals. Combination pharmacotherapy with agents that act on different receptors or neurotransmitter systems (e.g., naltrexone plus dexfenfluramine) may be one way to enhance serotonergic effects on drinking behavior and should be considered in future medication development clinical trials.

Inhibition of cytochrome P450 2D6 modifies codeine abuse liability

Oral codeine preparations, widely used for analgesia and cough suppression, are abused by some individuals for their mood-altering properties. The enzymatic O-demethylation of codeine is catalyzed by cytochrome P450 2D6 (CYP2D6), leading to the production of metabolites (morphine, morphine-6-glucuronide) that are pharmacologically more potent than codeine. A placebo-controlled, single-blind study was conducted to characterize the subjective effects of codeine associated with abuse liability and to determine the importance of metabolic O-demethylation to codeine abuse liability. Twelve non-drug-dependent subjects received oral administration of placebo and codeine 60, 120, and 180 mg, and a favorite dose (FD) was determined for each subject. The FD was readministered after pretreatment with placebo, 50 mg of quinidine (a specific, selective CYP2D6 inhibitor) once, or 50 mg of quinidine given four times a day for 4 days. Single-dose quinidine pretreatment significantly decreased the recovery of O-demethylated metabolites in plasma (p < 0.01) and resulted in a decrease in the positive (e.g., "high," p < 0.05) and negative (e.g., nausea, p < 0.05) subjective effects of codeine in both the FD120 and FD180 groups. Short-term quinidine pretreatment inhibited codeine O-demethylation more than did single-dose quinidine pretreatment (p < 0.01), and it decreased positive codeine effects in the FD120 group (N = 7), but unexpectedly not in the FD180 group (N = 5). These results suggest that the O-demethylated metabolites contribute substantially to the subjective effects and abuse liability of codeine.

Inhibition of cytochrome P450 2A6 increases nicotine's oral bioavailability and decreases smoking

BACKGROUND

Nicotine establishes and maintains tobacco dependence. Individuals with genetically deficient CYP2A6 nicotine metabolism are at lower risk to become smokers and, if dependent, will smoke fewer cigarettes. Hepatic CYP2A6 accounts for nicotine's low systemic bioavailability, precluding oral nicotine replacement to treat dependence.

OBJECTIVE

We sought to determine whether CYP2A6 inhibition via oral methoxsalen decreases nicotine clearance, increases nicotine bioavailability, and decreases smoking.

METHODS

Two within-subject designs in healthy tobacco-dependent volunteers were conducted: a singleblind kinetic study (n = 17) of methoxsalen 30, 10, or 3.5 mg or placebo given with nicotine 4 mg orally to abstinent smokers; and a double-blind randomized crossover study (n = 11) of methoxsalen 30 mg or placebo crossed with nicotine 4 mg given orally or placebo before 60 minutes' abstinence and 90 minutes' free smoking.

RESULTS

Placebo plus nicotine 4 mg orally increased the mean 3-hour plasma nicotine level by 4 ng/mL over residual baseline nicotine level, whereas methoxsalen 10 or 30 mg plus nicotine increased it by 9 ng/mL (P<.01), demonstrating in vivo inhibition of CYP2A6 nicotine metabolism. Methoxsalen 30 mg plus nicotine 4 mg given orally decreased breath carbon monoxide concentration at the end of free smoking by 47% (4.6 versus 8.7 ppm; P<.01) and cigarettes smoked by 24% (3.1 versus 4.1, P<.01) compared with placebo plus placebo.

CONCLUSIONS

Methoxsalen inhibits nicotine first-pass metabolism of orally administered nicotine, and the combination directly reduces smoking in a laboratory setting. CYP2A6 inhibitors may have an important role in smoking cessation and tobacco exposure reduction.

Attenuation of the euphoric effects of cocaine by the dopamine D1/D5 antagonist ecopipam (SCH 39166)

BACKGROUND

The subjective and reinforcing effects of cocaine in humans are associated with the enhancement of endogenous dopamine function in the mesolimbic system. This study examined the role of dopamine D1-like receptors in the behavioral and mood effects of cocaine by evaluating the effects of the selective D1/D5 antagonist ecopipam (SCH 39166) on subjective responses to intravenous cocaine in 11 subjects with cocaine dependence as defined by DSM-IV.

METHODS

Subjects were pretreated in a randomized double-blind fashion with either placebo or 10 mg, 25 mg, or 100 mg of ecopipam orally on 4 separate occasions. Two hours later a single intravenous injection of 30 mg of cocaine was administered. Subjective and cardiovascular responses were measured and blood samples for pharmacokinetic evaluation were obtained prior to cocaine dosing and at various times after dosing.

RESULTS

The euphoric (P = .004) and stimulating (P = .03) effects of cocaine were attenuated in a dose-dependent manner by ecopipam, while ratings of desire to take cocaine were diminished (P = .02). Ecopipam in combination with cocaine was safe and well tolerated.

CONCLUSION

These data indicate a potentially important role for D1-like receptors in the acute mood-altering and rewarding effects of cocaine in humans.

Identifying appropriate subjects for abuse liability studies using prestudy pharmacological testing

Drug abuse liability testing usually involves a subject population of individuals who are current or former drug abusers. To determine whether choosing subjects from a wider and more diverse population of nondrug abusers results in subjective response patterns that are pharmacologically associated with drug abuse liability, a series of studies were conducted using the prescription opiate hydromorphone and the barbiturate secobarbital to prescreen subjects before their acceptance into large multidrug, multidose abuse liability studies. The results of these prescreening studies show that there were some subjects who were not able to report consistently and reliably relevant drug effects, even though they received pharmacologically active doses as measured by objective indexes such as pupil diameter for the opiate study and psychomotor impairment for the barbiturate study. To test the consistency of these results, several of the subjects from the hydromorphone screening were retested with hydrocodone. The results demonstrate that subjects who were unable to report positive subjective effects of hydromorphone were also unable to respond appropriately to hydrocodone, and subjects who responded appropriately to hydromorphone in the prescreening study consistently responded to another opiate. Using this prescreening methodology has allowed sensitive and reliable data on the abuse liability of benzodiazepine agonists and partial agonists, barbiturates, carbamate compounds, amphetamines, selective serotonin reuptake inhibitors and prescription opiate compounds to be generated using a nondrug abusing population. In conclusion, due to the relative heterogeneity of a population of nondrug abusers compared with a drug abusing population, it is necessary to prescreen subjects for their ability to detect and report subjective drug effects, and to distinguish the effects of an active drug from those of placebo. Selecting subjects from this population has several advantages over selecting subjects from the drug abusing population that outweigh any inconvenience of this simple prescreening methodology.

Psychotropic effects of dextromethorphan are altered by the CYP2D6 polymorphism: a pilot study

Dextromethorphan is a nonopioid antitussive metabolized by cytochrome P450 2D6 (CYP2D6) to an active metabolite, dextrorphan. CYP2D6 is polymorphically expressed in humans, with 5 to 10% of Caucasians being homozygous deficient for the active form of the enzyme. In a pilot study, the authors investigated the pharmacologic effects of dextromethorphan in individuals phenotyped and genotyped as extensive metabolizers (EMs, N = 4) and poor metabolizers (PMs, N = 2) of CYP2D6 substrates. Dextromethorphan doses ranged from 0 to 6 mg/kg based on individual subject tolerance. All EMs tolerated 3 to 6 mg/kg dextromethorphan, whereas PMs barely tolerated 3 mg/kg dextromethorphan and therefore received lower doses. As shown in previous studies, plasma kinetics show profound differences in dextromethorphan metabolism between EMs and PMs. Dextromethorphan produced qualitatively and quantitatively different objective and subjective effects in the two groups. Objectively, PMs had greater psychomotor impairment, as measured by a joystick tracking task, compared with EMs on 3 mg/kg dextromethorphan (mean performance +/- SE, 95+/-0.5% for EMs vs. 86+/-6% for PMs; p < 0.05). At this dose, EMs also reported greater abuse potential compared with PMs (p < 0.05), and PMs reported greater sedation and dysphoria compared with EMs (p < 0.01). These data provide preliminary evidence that dextrorphan contributes to dextromethorphan abuse liability, and therefore PMs may be less likely to abuse dextromethorphan.

A controlled trial of ondansetron, a 5-HT3 antagonist, in benzodiazepine discontinuation

Serotonin is implicated in the etiology of anxiety disorders and in the anxiolytic actions of benzodiazepines. Preclinical studies with 5-HT3 receptor antagonists, including ondansetron, show they have anxiolytic properties and that ondansetron suppresses withdrawal anxiety after abrupt discontinuation of chronic benzodiazepine treatment. We evaluated the efficacy of ondansetron as an adjunctive medication in the discontinuation of benzodiazepines in long-term users. One hundred eight patients who had used alprazolam or lorazepam regularly for > 3 months entered, and 97 completed a randomized double-blind discontinuation treatment program during which they received either ondansetron 2 mg twice daily or placebo and flexibly tapered their benzodiazepine over a 6-week period. There were no significant differences between the patients who had entered and completed treatment. Three weeks postmedication, 63% of the patients discontinued use of benzodiazepine. The percentage of reduction of benzodiazepine daily dosage at all time points in the treatment trial was similar for the ondansetron and placebo groups. Ondansetron had no significant effects on severity of withdrawal symptoms or levels of anxiety. High placebo response may have prevented detection of an ondansetron effect. At 1 year follow-up, 68% of patients reported that they stopped using benzodiazepine. Patient characteristics were more important than ondansetron in tapered benzodiazepine discontinuation.

Inhibition of cytochrome P450 2D6 metabolism of hydrocodone to hydromorphone does not importantly affect abuse liability

Enzymatic conversion of hydrocodone to hydromorphone is catalyzed by cytochrome P450 2D6, which is inactive in about 7% of Caucasians [poor metabolizers (PMs)] and can be inhibited by quinidine pretreatment in the remainder [extensive metabolizers (EMs)]. If hydromorphone, having a substantially higher mu-receptor affinity than hydrocodone, contributes importantly to the physiological and subjective effects of oral hydrocodone, then PMs should be less responsive to the same doses, and quinidine pretreatment should cause EMs to temporarily respond as PMs. Seventeen EMs and 8 PMs who previously responded positively to hydromorphone s.c. received placebo and hydrocodone (10 mg, 15 mg and 22.5 mg p.o.) and were retested with their favorite dose after placebo or quinidine (100 mg) pretreatment; physiological and subjective measures were collected at base line and four times after drug administration, and urine was collected for 8 hr. EMs and PMs were equally responsive to oral hydrocodone, and quinidine had no consistent effect on their responses, even though quinidine abolished the pre-existing metabolic differences in hydromorphone production, as measured in urine. These data suggest only a small role of hydromorphone in eliciting abuse-related responses to oral hydrocodone.

Clinical aspects of chronic use of alprazolam and lorazepam

OBJECTIVE

The authors' goal was to determine the clinical characteristics of persistent users of alprazolam or lorazepam who wished to discontinue their medication.

METHOD

Long-term users (daily use for more than 3 months) of alprazolam (N = 34) or lorazepam (N = 97) who entered an outpatient treatment program for discontinuation of benzodiazepines were carefully assessed. Detailed histories of benzodiazepine use were obtained; a structured interview was used to make psychiatric diagnoses based on DSM-III-R criteria.

RESULTS

The majority of patients were using low therapeutic doses of medication (lorazepam: mean = 2.7 mg/day; alprazolam: mean = 1.2 mg/day) and had either maintained their initial daily dose over time or decreased it. Individuals tended to shift their use of medication from an as-prescribed to an as-needed pattern. Forty-seven percent of the patients were diagnosed with at least one current anxiety disorder, most commonly generalized anxiety. At least one diagnosable personality disorder was found in 45% of the patients, most commonly obsessive-compulsive personality disorder. Patterns of benzodiazepine use were influenced by age, gender, and past history of alcohol dependence.

CONCLUSIONS

Long-term users of alprazolam/lorazepam seeking treatment for discontinuation had clinically important past and current psychiatric histories. They used a constant or decreasing dose of medication and made attempts to stop their use. Persistent use of alprazolam/lorazepam for therapeutic purposes did not represent abuse or addiction as the terms are usually understood. A substantial proportion of these patients may be receiving appropriate maintenance therapy for a chronic psychiatric condition.

Comparative abuse liability of sertraline, alprazolam, and dextroamphetamine in humans

Sertraline is an effective antidepressant acting as a selective serotonin reuptake inhibitor. The subjective and behavioral effects of sertraline were studied and compared with the effects of alprazolam and dextroamphetamine in a within-subject, randomized, double-blind study in 20 volunteers aged 18 to 46 years. These subjects were experienced but nondependent users of central nervous system depressants who had the ability to reliably distinguish secobarbital, 150 mg, from placebo and to report positive subjective effects of secobarbital in an experimental setting. The following drug conditions were tested: sertraline, 100 and 200 mg; alprazolam, 1 mg; dextroamphetamine, 10 mg; and placebo. Drug effects were assessed with an objective test of psychomotor performance, subject-rated questionnaires, and observer-rated scales. Both alprazolam and dextroamphetamine were distinguishable from placebo on most measures, but sertraline produced effects discernable from placebo on only a few measures. At 1 hour postdrug administration, dextroamphetamine and alprazolam produced positive effects on several measures of elation, euphoria, and drug liking greater than placebo and both doses of sertraline. In contrast, sertraline produced higher scores on measures of dysphoria and physical unpleasantness than did the other drug conditions. Observer ratings of satisfaction with the drug and other pharmacologic effects were consistent with these findings. Results from this study indicate that sertraline, at the doses tested, does not possess the behavioral effects profile considered to be indicative of abuse potential when compared with alprazolam and dextroamphetamine.

Pharmacologic effects and abuse liability of bretazenil, diazepam, and alprazolam in humans

OBJECTIVES

To assess the pharmacologic effects and abuse liability of bretazenil, a partial benzodiazepine agonist, and compare them to the short-term effects of diazepam and alprazolam over a range of doses.

METHODS

This was a placebo, within-subject, randomized, double-blind study conducted in 28 male volunteers. They were experienced but nondependent users of central nervous system depressants who had the ability to reliably distinguish 150 mg secobarbital from placebo and to report positive subjective effects. Subjects randomly received placebo and the two middle doses of diazepam, bretazenil, and alprazolam for the first 7 days of the study and, depending on their clinical response, received either the highest or the lowest dose of each drug for the remaining 3 days. Pharmacologic effects were assessed by use of objective tests (e.g., psychomotor performance), subject-rated questionnaires (e.g., Profile of Mood States), and observer-rated scales.

RESULTS

All three drugs were clearly distinguishable from placebo on most measures. Diazepam and alprazolam produced dose-related psychomotor and memory impairment, whereas bretazenil produced a flatter slope. Both alprazolam and diazepam produced dose-dependent increases in subject and observer-rated sedation and liking, whereas bretazenil showed increases compared with placebo, but these effects were not dose dependent.

CONCLUSIONS

Results from the study supported the view that bretazenil may have a partial agonist pharmacologic profile. Scores on subjective effects scales considered important for abuse liability assessment suggest a lower abuse liability of bretazenil than diazepam and alprazolam.

CYP2D6 phenotype determines the metabolic conversion of hydrocodone to hydromorphone

The contribution of cytochrome P450 2D6 (CYP2D6) to the formation of hydrocodone's active metabolite, hydromorphone, was examined in vitro and in vivo. Human liver microsomes prepared from an individual homozygous for the D6-B mutation of the CYP2D6 gene catalyzed this reaction at a negligible rate. Urinary metabolic ratios of hydrocodone/hydromorphone were highly correlated with O-demethylation ratios for dextromethorphan, an established marker drug of CYP2D6 activity (rs = 0.85; n = 18). The kinetics of hydrocodone after a single oral dose and its partial metabolic clearance to hydromorphone were investigated in five extensive metabolizers of dextromethorphan, six poor metabolizers, and four extensive metabolizers after pretreatment with quinidine, a selective inhibitor of CYP2D6 activity. The mean values for partial metabolic clearance by O-demethylation in the three groups were 28.1 +/- 10.3, 3.4 +/- 2.4, and 5.0 +/- 3.6 ml/hr/kg, respectively. No statistically significant phenotypic differences in physiologic measures were observed. However, over the first hour after dosing, the extensive metabolizers reported more "good opiate effects" and fewer "bad opiate effects" than poor metabolizers and extensive metabolizers in whom CYP2D6 was inhibited by quinidine. These data establish the importance of CYP2D6 in the formation of hydromorphone from hydrocodone and suggest that the activity of this enzyme may limit the abuse liability of hydrocodone.

Characteristics of long-term alprazolam users in the community

The widespread use of benzodiazepines remains a source of concern to the medical profession and the general public, especially as newer compounds come on the market. Our goal was to characterize long-term alprazolam users in the community and to determine whether such use represented abuse or behavioural dependence. We conducted three community surveys to learn about the natural history of long-term alprazolam use. Current long-term alprazolam users (those using the drug for 3 months or longer) were recruited on three separate occasions 1 year apart by identical newspaper advertisements in the metropolitan Toronto area. All respondents were mailed a questionnaire with a stamped, addressed return envelope. Our data from 312 respondents show that: (1) the majority of patients have a substantial history of prior medication use for symptom control (65%), (2) dose escalation is not a characteristic of long-term use, (3) patients change their initial pattern of regular use to one of symptom control only when required, (4) most physicians do not discuss discontinuation of the drug with their patients, (5) patients frequently try to stop their drug use (with a median of 2 attempts) and often report symptoms upon discontinuation, and (6) patients perceive a need for medication use and indicate that alprazolam is effective (75%). We conclude that some patients persistently use alprazolam but that this use does not represent abuse or behavioral dependence.

Comparative drug effects and abuse liability of lorazepam, buspirone, and secobarbital in nondependent subjects

The pharmacologic effects of lorazepam (2 mg), buspirone (20 mg, 10 mg), secobarbital (100 mg), and placebo were compared in 15 male, experienced, intermittent nontherapeutic drug users. All drugs produced a "drug effect," however, buspirone 20 mg was significantly less liked than were lorazepam, secobarbital, or buspirone 10 mg (p less than .05) but not placebo. Lorazepam was liked better than were other drugs only at 1 hour and only compared with buspirone 20 and placebo. Compared with other drugs, lorazepam drug effects were greater and resulted in more prolonged impairment of a motor tracking task, standing steadiness, and memory. Buspirone 20 mg significantly impaired memory at 1 hour compared with placebo. Subjects were more likely to identify buspirone as unfamiliar. Because buspirone 20 mg was less liked than were other drugs, dose escalation as part of drug abuse is not likely to occur. Lorazepam also was not particularly liked and was not different from placebo on most subjective abuse-relevant measures.

Kinetic and dynamic interactions of oral viqualine and ethanol in man

We have studied the interaction of viqualine, a 5-hydroxytryptamine (5-HT) uptake inhibitor, with ethanol in 16 healthy men aged 20 to 34 years. The subjects were randomly assigned to receive ethanol dosed to maintain blood alcohol concentrations of 17-22 mmol.l-1 (n = 8) or orange juice (n = 8) on each of two test days one week apart and preceded, in random order, by 3 days of viqualine 75 mg bd or placebo. Ethanol had no effect on steady-state viqualine concentrations or the inhibition of 5-HT uptake. Viqualine did not affect acetaldehyde concentrations or cause an aversive alcohol-sensitizing reaction. The deleterious effects of ethanol on word recall, manual tracking, body sway, and self-ratings of intoxication, sedation, and performance were not modified by the presence of viqualine. Within each beverage group performances and self-ratings on viqualine and placebo days were not different. The first dose of viqualine was associated with transient nausea. Viqualine and ethanol do not interact kinetically or dynamically on the variables examined in this study.

Limitations in the measurement of urine ethanol in clinical trials to monitor ethanol consumption

Self-report of daily alcohol consumption has been used as the dependent variable in clinical trials to assess the effects of two serotonin uptake inhibitory drugs, zimelidine and citalopram. The validity of the dairy data was established by correlating concentration of ethanol in daily urine samples with number of reported standard alcoholic drinks (r = 0.62 for the 934 subject-days in the zimelidine study; r = 0.54 for the 3,103 subject-days in the citalopram study, both p less than 0.0001). The effects of factors other than inaccurate reporting, such as the range of values for reported daily drinks and subjects' drinking patterns, on the correlation coefficients for all subject-days and for individual subjects in the citalopram study are discussed. Sampling 50% or fewer of the 84 days of the citalopram study for each subject is economically advantageous and did not significantly change the values of the correlation coefficients or the rank positions of subjects but did increase the 95% confidence intervals for the correlation coefficients, indicating less certainty about the actual correlation coefficients and, therefore, the accuracy of a subject's self-report. The ability of urine ethanol concentration to validate objectively diaries of alcohol consumption is limited by factors that must be considered but are likely to be out of the investigator's control.

Comparative neurologic effects of diazepam and suriclone, a cyclopyrrolone anxiolytic

Suriclone selectively displaces benzodiazepines from their binding sites but is structurally unrelated to benzodiazepines. Neurologic effects of suriclone were compared to those of diazepam in 54 subjects in a sequential, double-blind, single dose, randomized study (placebo; diazepam 10 mg; suriclone 0.2, 0.4, 0.6, or 0.8 mg). Data were collected on-line by microcomputer. Suriclone 0.2 mg did not differ from placebo. Suriclone 0.4 mg and 0.6 mg did not differ from diazepam 10 mg. Suriclone 0.8 mg caused significantly more decrement than diazepam 10 mg (p less than 0.05) in manual tracking, force platform stability, and Heath rail walking and in total severity of symptoms. Suriclone 0.8 mg caused nausea (p = 0.02), clumsiness (p = 0.02), and loss of balance (p = 0.01) more frequently than diazepam 10 mg. Suriclone 0.8 mg produced symptoms and signs qualitatively and quantitatively different from diazepam 10 mg, such as vomiting, unusual ocular movement effects, and difficulty walking. Possibly the differences in CNS drug binding for anxiolytics are associated with clinical differences in toxicity.

Effects of hydrogen chloride on respiratory response and pulmonary function of the baboon

The effects of hydrogen chloride (HCI) inhalation on respiratory response during exposure and on pulmonary function during the 3 mo following exposure were studied in the baboon. Each of 4 groups of three anesthetized animals was exposed in a head-only mode for 15 min to air or one of three HCI concentrations (500, 5000, or 10,000 ppm). The acute respiratory response consisted of a concentration-related increase in frequency and minute volume, with a marked decrease in blood PaO2 at the two highest concentrations. The exposures did not cause significant alterations in any of the pulmonary function parameters measured at 3 d and 3 mo postexposure. Thus, nonhuman primates were able to survive short exposures to high concentrations of HCI without any significant effects on pulmonary function during the 3 mo after exposure. Furthermore, comparison of the response of primates and rodents suggests that the human is much less sensitive to the effects of HCI than the mouse.

Effects of irritant gases on avoidance/escape performance and respiratory response of the baboon

The major toxicants in smoke are generally categorized as asphyxiants (hypoxia-producing agents) and irritants. Although the rodent appears to be an adequate model for evaluating the toxic effects of asphyxiant gases in man, the suitability of the rodent for evaluating the effects of irritant gases has not been established. In a study of the effects of irritant gases on escape performance of the baboon, exceedingly high concentrations of neither acrolein nor hydrogen chloride (HCl) prevented performance of the behavioral task; however, severe irritant effects were evident, even at lower concentrations. In a subsequent study of the respiratory response of the baboon to HCl, 15-min exposures to 5000 and 10,000 ppm (nominal concentrations) produced severe hypoxemia with a concentration-related increase in respiratory rate and minute volume. The difference between the rodent and the nonhuman primate in response to irritant gases suggests that the rodent may be an inadequate model for evaluating the toxicity of irritant gases to man and, therefore, the use of results of laboratory combust combustion tests to predict the toxicity of smoke in humans may lead to erroneous conclusions.

Triazolam and ethanol interaction: kinetic and dynamic consequences

The kinetic and dynamic consequences of the coadministration of triazolam and ethanol were investigated in six normal subjects. Each received three treatments: triazolam, 0.25 mg by mouth, preceded by 1 hour and followed for 7.5 hours by oral ethanol dosed to maintain breath concentrations of 800 to 950 mg/L; placebo and ethanol; and triazolam and orange juice. After ethanol, triazolam total AUC0-infinity increased (mean +/- SD = 21% +/- 18%). Subjects showed greater psychomotor impairment on measures of free recall, postural stability, and hand-eye coordination after the combination than after either drug alone. These dynamic interactions are greater than the kinetic changes.

Is there acute tolerance to alcohol at steady state?

Although acute tolerance to the psychomotor impairment caused by alcohol has been documented in single-dose studies, the pharmacodynamic effects of continued alcohol administration in humans have not been well studied. Six nonalcoholic men received alcohol to achieve and maintain breath alcohol levels of 80-100 mg/dl for 6 hr. The men suffered an initial impairment in word recall but improved over the next 6 hr. Measures of standing steadiness and manual tracking did not show evidence of the development of tolerance. This lack of tolerance was reflected in subjects' self-assessments of sedation and intoxication.

Pharmacokinetic interaction of propoxyphene with ethanol

In order to study the effects of ethanol on the pharmacokinetics of propoxyphene, six healthy male volunteers were each given (1) propoxyphene 65 mg p.o. preceded by 1 h by ethanol 0.9 g/kg lean body weight and followed for 7.5 h by ethanol dosed to maintain breath ethanol at 800-1000 mg/l; and (2) propoxyphene 65 mg p.o. with orange juice in the same volume and frequency as ethanol. Ethanol did not induce any significant changes in apparent t 1/2 or Cmax of propoxyphene or norpropoxyphene. The average norpropoxyphene/propoxyphene ratio decreased by a mean 36%.

Acute kinetic and dynamic interactions of zimelidine with ethanol

The acute interaction of zimelidine (Z) with ethanol (E) was examined in six healthy men aged 20 to 37 yr who randomly received each of four treatments 1 wk apart: Z, 200 mg by mouth, preceded by 1 hr and followed for 7 hr of oral E in juice dosed to maintain blood alcohol concentrations between 800 and 1000 mg/l; placebo Z and E; Z and juice; and placebo Z and juice. E decreased the rate of biotransformation of Z to norzimelidine (NZ) by 46%, but the AUCs of Z, NZ, and their total concentration over 8 hr were not altered by E. Acetaldehyde concentrations did not change and no aversive alcohol-sensitizing reaction was detected. E-induced impairments in memory, body sway, and a manual tracking task were further enhanced by Z, as was the E-induced decrease in friendliness. Data suggest Z and E interact kinetically and dynamically and suggest a mechanism whereby Z may decrease E intake in man.

Diazepam tapering in detoxification for high-dose benzodiazepine abuse

The clinical characteristics and management of patients who abuse high doses of benzodiazepines are not well described. In a prospective open study, 23 subjects who abused high doses of benzodiazepines were admitted for detoxification. Urine or blood test results confirmed benzodiazepine use in all but one subject and multiple drug use in eight (35%). Median benzodiazepine dose was 150 mg (range 40 to 500 mg) of diazepam equivalent. Initial plasma concentrations (diazepam: median = 1245 ng/ml; desmethyldiazepam: median = 2961 ng/ml) were 400% to 800% higher than usual therapeutic concentrations. For detoxification, subjects were given a loading dose of diazepam equal to approximately 40% their reported daily consumption. This was followed with daily tapering of diazepam by 10%. This regimen resulted in a slow and gradual decline in drug concentrations. Withdrawal symptoms were assessed daily. Sixteen subjects completed detoxification in the hospital without complications. One subject became paranoid and confused on day 7 of withdrawal. This was attributed to a too-low initial loading dose and too-rapid tapering, which resulted in rapid drug elimination. Gradual reduction of diazepam dose appears to be an effective and safe approach for detoxifying abusers of high doses of benzodiazepines.

Ethanol-induced inhibition of hepatic uptake of propranolol in perfused rat liver and in man

Studies were conducted to determine the mechanism whereby ethanol alters the hepatic disposition of propranolol. In eight isolated perfused rat livers, ethanol (mean = 40.1 mmol/l diminished the clearance of dl-propranolol (1.93 +/- 0.43 to 1.24 +/- 0.22 ml/min/g liver, p less than 0.05); increased its t1/2 (12.8 +/- 1.5 to 20.7 +/- 3.25 min, p less than 0.01); and decreased the proportion metabolized (68.7 +/- 4.7% to 34.3 +/- 10.3%, p less than 0.01). These results suggest that ethanol could substantially increase the oral bioavailability of propranolol in humans. However, in normal human volunteers administered 80 mg of propranolol orally, alone, or preceded and followed by ethanol to maintain breath ethanol concentrations of 800-1000 mg/l, increases in propranolol AUC were smaller than anticipated. Seven subjects had increases in free propranolol AUC0-8h (32%, range: 12-61%) (p less than 0.05), while total propranolol AUC0-8h increased by a mean 22% (range: -4-+49%). Propranolol free fraction varied with time and was higher after ethanol (mean = 0.090 vs 0.084) (p less than 0.077). The extent of the propranolol-induced slowing of heart rate was not influenced by ethanol (mean decrease from baseline of 13 bpm at peak propranolol effect vs 9 bpm without ethanol); mean heart rates following propranolol with ethanol were higher at all times (mean of 7.5 bpm) (p less than 0.001) than after propranolol alone. Ethanol inhibits the hepatic oxidative metabolism of propranolol in vitro; however, any effect on heart rate of higher concentrations of propranolol induced by ethanol in humans is offset by the cardio-acceleratory effect of ethanol.

Amitriptyline and ethanol: pharmacokinetic and pharmacodynamic interaction

Amitriptyline has clinically important interactions with ethanol. Five healthy volunteers received 25 mg of amitriptyline orally, preceded by one hour and followed for eight hours by oral ethanol (or juice), dosed to achieve and maintain blood ethanol concentrations of 800 mg/l. In the presence of ethanol, amitriptyline free plasma concentrations were increased by a logarithmic mean of 204%, 186% and 127% at 1.5, 2, and 2.5 h, respectively, and amitriptyline free AUC0-8h was increased by 48% +/- 13% (means +/- SEM) (t = 5.21, p less than 0.01). Nortriptyline total AUC0-8h was increased by 26.6% +/- 12% (means +/- SEM) (t = 2.21, p less than 0.09). At the time of peak amitriptyline plasma concentrations, mean postural sway was increased over baseline by 92% with, and 2% without ethanol; likewise, mean short term memory (word recall) was decreased over baseline by 71% with, and 37% without ethanol. Ethanol increases free amitriptyline plasma concentrations most dramatically during the period of drug absorption; this is due to a decrease in amitriptyline hepatic clearance, resulting in decreased first-pass extraction. Together with the pharmacodynamic interaction, the kinetic changes provide a rationale for the toxicity of this combination and its deleterious effects on psychomotor skills.

Development of optimal treatment tactics for alcohol withdrawal. I. Assessment and effectiveness of supportive care

The relative roles of supportive care and pharmacotherapy in the treatment of alcohol withdrawal are not established. A reliable and validated withdrawal severity assessment scale (Clinical Institute Withdrawal Assessment for Alcohol, CIWA-A) was developed to assess initially and then follow the clinical course of 38 hospitalized chronic alcoholics requiring hospitalization for withdrawal but without serious concurrent medical or surgical problems. Supportive care, consisting of standardized half-hourly patient assessment (CIWA-A) and nursing care, was used as the initial treatment for all patients. Twenty-eight (74%) patients with clinical supportive care successes within 8 hours, 75% within 4 hours. Two responding patients subsequently developed evidence of withdrawal at 48 hours (hallucinations) and 72 hours (seizure). Ten patients (26%) did not respond to supportive care and required drug therapy in addition. Responders to supportive care drink more by history and have less severe liver disease than nonresponders. There are no other apparent predictors of the patients who require drug therapy. Three quarters of hospitalized patients, without serious medical complications, in alcohol withdrawal respond to intensive supportive care. However, pharmacotherapy is essential for nonresponders and patients with hallucinations.

Electroencephalographic tolerance and abstinence phenomena during repeated alcohol ingestion by nonalcoholics

Certain measures of the auditory average evoked response are sensitive to alcohol and provide evidence for abstinence and tolerance during and after 10 days of alcohol consumption by nonalcoholics. Electroencephalographic techniques provide a single sensitive measure for the study of the etiology of tolerance and abstinence with particular reference to a new area of investigation with nonaddicted humans.

Acute and chronic drug abuse emergencies in Metropolitan Toronto

From 3,548 drug overdose or abuse cases presenting at 21 Metropolitan Toronto hospitals' Emergency departments, data concerning demographic and medical characteristics, investigative and management procedures, drug analysis services, and disposition of patients were collected. Of the 3,548 cases, 2,723 (77%) were acute overdose and 816 (23%) were drug abuse. Drug overdose was more common than drug abuse for both sexes, but was more characteristic of females. The drugs most frequently alleged ingested were benzodiazepines (34%), ethanol (32%), salicylates (16%), and barbiturates (14%). The frequency with which particular classes of drugs are alleged in overdose corresponds closely to the frequency of prescribing these drugs in Ontario.

Alcohol use by patients admitted to hospital emergency rooms for treatment of drug overdose and misuse

Persons admitted to hospital emergency rooms for treatment of drug misuse with concomitant alcohol use were generally found to be heavy drinkers.

EEG correlates of the alcohol-induced organic brain syndrome in man

Fourteen chronic alcoholics were studied within 1 to 3 weeks of beginning abstinence for a duration of 6 to 10 weeks. Patients were drug-free during the study. Electroencephalograms were recorded on admission, and twice at 2- to 3-week intervals. Neurologic examinations were performed during the same week as EEGs, and patients received a psychologic examination and CT scan within 3 weeks. Two groups could be identified. One group had high neurologic impairment scores, low alpha production, high 20 to 30 Hz power, impaired gait, and mental performance, while the other had low scores, normal alpha rhythm, and reduced degree of mental dysfunction. The impaired group showed marked improvement in neurologic scores, alpha rhythm, and 20 to 30 Hz power within 4 to 6 weeks, in contrast to no change for the unimpaired group. There was no evidence that age, duration of drinking, time from last drink, or cortical atrophy were involved in predisposing alcoholics to demonstrate the observed changes. It is submitted that spontaneous recovery in brain function of neurologically impaired alcoholics accompanies abstinence from chronic alcohol consumption.

Benzodiazepine-associated emergencies in Toronto

In a prospective study of drug overdose patients admitted to emergency rooms of 21 Toronto hospitals, 39% said they had taken a benzodiazepine. Benzodiazepines were used more frequently by females than males and by suburban than core hospital patients. Patients who overdosed on benzodiazepines were admitted to the hospital less frequently and arrived with less disturbance of consciousness than those who had used other drugs. Patterns of prescription in Ontario and patterns of overdose in Metropolitan Toronto were highly correlated.

Adverse biochemical and clinical consequences of furosemide administration

Nurse monitors collected clinical and laboratory data from 204 hospitalized patients receiving furosemide (122 men and 82 women; mean age 69.6 years). Biochemical abnormalities and clinical problems definitely or probably induced by any drug occurred in 70.6% and 49.0% respectively of the patients, and were attributed to furosemide in 81.3% and 13.0% respectively of these patients. The most important clinical events were dehydration and hypotension. Furosemide-induced hypochloremia, hypokalemia and hyponatremia occurred in 35.8%, 25.0% and 24.5% of the patients respectively. Most of the biochemical changes were slight, and only 3.9% of the patients had a furosemide-induced decrease in the serum potassium concentration to less than 3.0 mmol/L. Surprisingly, 24.5% of the patients also manifested drug-induced hyperkalemia. Administration potassium supplements or spironolactone, or both, concurrently with furosemide was responsible in most cases for the development of hyperkalemia. The occurrence of drug-induced adverse effects after 2 weeks of hospitalization was significantly associated (P less than 0.05) with subsequent prolongation of hospitalization. The high frequency of drug-induced events warrants careful monitoring of all patients receiving furosemide in spite of the low frequency of serious toxic effects produced by the drug.