Reversal of ethanol intoxications in humans: an assessment of the efficacy of propranolol

The medico-legal significance of pharmacokinetic interactions with ethanol

In the UK, the maximal permitted ethanol concentration for driving is 80 mg ethanol/100 mL blood, 35 μg ethanol/100 mL breath or 107 mg ethanol/100 mL urine. Drivers exceeding the prescribed limit face severe penalties, which they are often anxious to avoid, either by acquittal or by putting forward 'special reasons' why they should not be disqualified from driving. One frequently explored defence is that the accused was taking prescribed medication. Defence solicitors often ask the question whether the prescribed medication could have caused significantly altered blood ethanol concentrations. This paper reviews the impact of various medications and how they can influence the blood ethanol concentration. Although many drugs can interact with ethanol at a pharmacodynamic level, causing increased impairment, relatively few drugs interact with ethanol pharmacokinetically leading to significantly altered blood ethanol concentrations.

[Clinical Practice Guide for Early Detection, Diagnosis and Treatment of the Acute Intoxication Phase in Patients with Alcohol Abuse or Dependence: Part II: Evaluation and Management of Patients with Acute Alcohol Intoxication]

INTRODUCTION

Worldwide, alcohol is the second most-used psychotropic substance and the third risk factor for early death and disability. Its noxious use is a world public health problem given its personal, labor, family, economic and social impact. The identification of acute alcohol intoxication is extremely important, as well as the alcohol withdrawal syndrome and its complications, such as delirium tremens and Wernicke's encephalopathy in order to grant a timely treatment for those patients. This article introduces the evidence found so as to face and treat these clinic manifestations.

METHODOLOGY

Systematic revision of the evidence available together with an evaluation of pertinent guidelines found in literature so as to decide whether to adopt or adapt the existing recommendation for each question or to develop de novo recommendations. For de novo recommendations as well as those adapted, it was carried out an evidence synthesis, together with evidence tables and formulation of recommendations based on the evidence.

RESULTS

Evidence was found and recommendations were made for the diagnosis and treatment of acute alcohol intoxication, withdrawal syndrome, delirium tremens and Wernicke's encephalopathy.

Combined effects of propranolol and ethanol on human psychomotor performance

Twelve male subjects were given placebo or 160 mg propranolol, in divided doses, during a 24-hr period before drinking a beverage containing 0 or 50 ml ethanol/70 kg body weight. Tests designed to measure mental and motor performance were administered 75 min after the last dose of propranolol. The tests performed included the wobble board (WB), pursuit meter (PM), delayed auditory feedback (DAF), pegboard (PB), tapping, time estimation (TE), and a modified Cornell medical index (CMI). A mean blood ethanol concentration of 48.0 +/- 9.1 mg/dl and a mean plasma propranolol level of 33.1 +/- 13.1 ng/ml were achieved. Ethanol alone significantly impaired performance in 12 out of 20 tests (p less than 0.05). Propranolol significantly (p less than 0.05) antagonized the decrement in psychomotor performance induced by ethanol on the PM. In all other tests, there was no significant interaction between ethanol and propranolol. Propranolol alone had no significant effect on the psychomotor tests. When the drugs were combined, the subjective symptoms, as measured by the CMI, showed a trend toward being additive. This study suggests that no adverse interaction occurs between therapeutic doses of propranolol and minimum impairment doses of ethanol.

Interaction of apomorphine and amantadine with ethanol in men

Male moderate drinkers (n = 12) drank ethanol (0.8 g/kg) and then ingested one of the following: apomorphine (5 mg), amantadine (200 mg), or placebo. Subjects were tested on a battery of physiological and behavioral measures using a double-blind, within-subjects, crossover design. Postethanol ingestion of apomorphine significantly increased ethanol's effect on 3 out of the 8 measures employed (divided attention, objective and subjective inebriation ratings) without significantly altering blood ethanol concentrations or the rate of blood ethanol decline. There was no indication that apomorphine antagonized ethanol's effects. In contrast to reports indicating that amantadine antagonized ethanol depression in rodents, amantadine did not significantly alter the degree of ethanol intoxication in humans. The increase in intoxication induced by apomorphine supports suggestions that dopaminergic systems may be involved in mediating ethanol intoxication and that the sobering effect of catecholamine-augmenting drugs results from noradrenergic, rather than combined noradrenergic and dopaminergic, stimulation. Further studies are necessary to elucidate the role of pre- and postsynaptic dopaminergic receptors in mediating these effects.

Self reports on alcohol use and compliance with antihypertensive medication

Adverse effects of alcohol drinking were investigated in 240 hypertensive patients. Perceived interaction between alcohol and antihypertensive medication was reported by 9.9% of patients but the symptoms were rather mild. Except for the fact that the patients who perceived drug-alcohol interaction had higher diastolic blood pressure than the rest of the patients there was no evidence that alcohol use decreased compliance with antihypertensive treatment. Most heavy alcohol users believed that they should take their antihypertensive medication while drinking and reported doing so. Indiscriminate emphasis on avoidance of drug-alcohol combination might decrease blood pressure control of these patients.

Beta-blockers in the treatment of neurological and psychiatric disorders

Beta-blockers, originally introduced into clinical practice for the treatment of cardiovascular disorders, are being increasingly advocated in the treatment of diverse neurological and psychiatric conditions. Thus, propranolol and certain other beta-blockers have been shown to be effective, and may be the drugs of choice, in the treatment of benign essential tremor and the prevention of recurrent migraine attacks. These drugs also have a useful role to play in the treatment of anxiety and alcohol withdrawal states, although beta-blockers have not come into general use in these conditions. The action of propranolol and related drugs in these neurological and psychiatric conditions is generally considered to be mediated by blockade of peripheral beta-adrenergic receptors, although other effects, either central or peripheral, may also be involved. The use of beta-blockers in the treatment of psychosis remains controversial. Current evidence does not support the use of propranolol in schizophrenia, but further studies in mania are warranted.

Adverse psychiatric reactions to modern medication

From this survey it will be apparent that many psychiatric reactions to drugs are largely caused by their direct toxic actions or from combinations of drugs. As such, they are often dose related, although age and slow speed of detoxification will increase the risk of patients developing delirium, hallucinations, sleep disturbances, anxiety etc. Similar toxic reactions can also occur when drugs to which a patient has developed some measure of tolerance are abruptly withdrawn. In this context the effects of drugs upon patterns of sleep may be important determinants of adverse withdrawal symptoms. In contrast are the reactions which resemble one or other of the functional psychoses. In these patients it appears that a past history of an affective or schizophrenic psychosis is the best predictor of a similar illness being precipitated by a particular drug. Nonetheless, with substances like reserpine and cycloserine there is good reason for thinking that, given a sufficient quantity, practically any patient can develop an adverse psychiatric reaction.

Alcohol intake and ethanol intoxication in the rate: effect of a 6-OHDA-induced lesion of the ascending noradrenaline pathways

The ascending noradrenaline (NA) pathways were lesioned by injecting 6-hydroxydopamine (6-OHDA) 16 micrograms/4 microliters bilaterally into the posterior mesencephalon in male Long Evans rats. Another group of rats was pretreated with protriptyline (25 mg/kg), a NA uptake blocking agent, 15 min before they received the intracerebral injections of 6-OHDA. The controls received the vehicle only. Spectrofluorimetric determination of the catecholamine concentrations in various parts of the brain revealed a marked degeneration of the ascending NA systems in the group receiving 6-OHDA. Unexpectedly, the DA systems were also affected by the 6-OHDA treatments. Three weeks after the operation the 6-OHDA group showed a transient increase in ethanol intake. In the tilting-plane test, ethanol (2 g/kg. i.p.) impaired the performance of the 6-OHDA-treated rats significantly more than that of the controls. In contrast, the hypothermic effect of ethanol (4 g/kg, i.p.) was significantly smaller in the lesioned rats. Furthermore, the catecholamine levels in various parts of the brain could be significantly correlated with both the extent of ethanol intoxication and the hypothermia. However, the duration of ethanol-induced narcosis (4 g/kg, i.p.) was affected by the present treatments. These results give further support for the view that the central NA neurons are important in the control of ethanol intake, and that they are involved in the expression of the acute effects of ethanol administration.

Alcohol intake, ethanol-induced narcosis and intoxication in rats following neonatal 6-hydroxydopamine or 5, 7-dihydroxytryptamine treatment

Newborn rats were treated with 5,7-dihydroxytryptamine (5,7-HT; 2 x 100 mg/kg s.c., 24 h interval) after pretreatment with desipramine (20 mg/kg s.c.) for depletion of brain 5-hydroxytryptamine (5-HT) or with 6-hydroxydopamine (6-OHDA; 3 x 100 mg/kg s.c., 24 h interval) for selective reduction of brain noradrenaline (NA). The 5,7-HT treatment resulted in a 53% reduction in endogenous 5-HT in the cerebral cortex and a 60% increase in the pons-medulla when determined in adult rats. The 5-HT content in the midbrain was not affected. Endogenous NA in the 6-OHDA treated animals was selectively reduced by 100% in the cerebral cortex, 35% in the midbrain and increased by 117% in the pons-medulla. No difference was found between the voluntary ethanol selection of these groups and that of the controls when measured at the age of 3 months. In a tilting-plane test, ethanol (2 g/kg i.p.) impaired the performance of the 6-OHDA treated rats significantly more than that of the controls. Moreover ethanol (4 g/kg e.p.) produced significantly longer narcosis in these rats. In contrast, the 5,7-HT treated rats were not affected significantly more than the controls in these tests. These results suggest that catecholamine neuronal systems interact with the expression of alcohol intoxication.

Reversal of ethanol intoxication in humans: an assessment of the efficacy of L-dopa, aminophylline, and ephedrine

The effect of postethanol treatment with L-Dopa, aminophylline and/or ephedrine was investigated. In one experiment, healthy, male, moderate drinkers ingested ethanol (0.8 g/kg) and then either L-Dopa (1.5 g), or placebo. In a second experiment, subjects ingested ethanol followed by aminophylline (200 mg), ephedrine (50 mg), aminophylline (200 mg) plus ephedrine (50 mg), or placebo. Double-blind, within-subjects, crossover designs were employed. Treatment with L-Dopa significantly reduced ethanol's effect on the electroencephalogram, motor coordination, and divided attention performance (t-test for paired data). Treatment with aminophylline and/or ephedrine also significantly reduced ethanol's effects on the electroencephalogram and motor coordination. The ethanol-antagonism may result from central noradrenergic stimulation.