Antidepressant drugs and ethanol: behavioral and pharmacokinetic interactions in mice

Mianserin, but not ondansetron, reduces the locomotor stimulating effect of ethanol in preweanling rats

During infancy rats are highly sensitive to the locomotor stimulating effect of ethanol, an effect particularly observed when they are tested during the rising phase of the blood ethanol curve and in a novel environment. According to a recent study infant rats require some degree of stress to get stimulated after being challenged with ethanol. Ethanol-induced stimulation in preweanling rats required the activation of CRH-1 receptors. Considering these antecedents, we explored modulation of the acute stimulating effect of ethanol (2.5g/kg) by two anxiolytic drugs, Mianserin (2.5 or 5mg/kg) and Ondansetron (1 or 3mg/kg). Mianserin attenuated the stimulating effect of ethanol at a dose that did not affect locomotor activity in water-controls, likely acting through 5-HT2 receptors, while Ondansetron, a 5-HT3 antagonist, did not affect this response. These results are consistent with recent findings indicating that one of the mechanisms by which the CRH-1 receptor modulates anxiety depends on sensitization of the 5-HT2 receptor antagonist, and highlight the importance of stress as a modulator of the effects of ethanol during early developmental stages.

Desipramine potentiation of the acute depressant effects of ethanol: modulation by alpha2-adrenoreceptors and stress

Ethanol exerts effects on the brain noradrenergic system, and these are thought to contribute to the sedative/hypnotic (depressant) effects of ethanol. Recent studies suggest that the norepinephrine transporter (NET) plays an important role in modulating ethanol's depressant effects. The aim of the present study was to further characterize this role. Transporter blockers with varying affinity for NET versus the serotonin transporter (desipramine>fluoxetine>citalopram) were tested for their ability to alter ethanol's depressant effects, and for comparison, hypothermic effects. Effects of desipramine on another depressant, pentobarbital, were examined. Desipramine potentiation of ethanol's depressant effects was assessed following depletion of brain norepinephrine via N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride (DSP-4) treatment, or depletion of brain 5-HT via para-chlorophenylalanine methyl ester hydrochloride (PCPA) treatment. The effects of co-administration of either the selective alpha2-adrenoreceptor agonist (dexmedetomidine) or the selective alpha2-adrenoreceptor antagonist (atipamezole) on desipramine's effect on ethanol's depressant effects were examined. Given the close link between stress, ethanol and norepinephrine, desipramine potentiation of ethanol's depressant effects was tested following repeated forced swim stress. Results showed that desipramine, but not SERT-selective doses of citalopram or fluoxetine, strongly potentiated the depressant (not hypothermic) effects of ethanol. These effects were mimicked by dexmedetomidine and blocked by atipamezole, but not by depletion of either norepinephrine or 5-HT. Desipramine potentiation of ethanol's depressant effects was abolished following repeated stress. Present findings further support a major role for NET and the alpha2-adrenoreceptor in modulating the depressant effects of ethanol, with possible implications for understanding the role of noradrenergic dysfunction in stress-related alcoholism.

Alcohol significantly lowers the seizure threshold in mice when co-administered with bupropion hydrochloride

BACKGROUND

Bupropion HCl is a widely used antidepressant that is known to cause seizures in a dose-dependent manner. Many patients taking antidepressants will consume alcohol, even when advised not to. Previous studies have not shown any interactions between bupropion HCl and alcohol. However, there have been no previous studies examining possible changes in seizure threshold induced by a combination of alcohol and bupropion HCl.

METHODS

Experimentally naïve female Swiss albino mice (10 per group) received either single doses of bupropion HCl (ranging from 100 mg/kg to 120 mg/kg) or vehicle (0.9% NaCl) by intraperitoneal (IP) injection in a dose volume of 10 ml/kg, and single-dose ethanol alone (2.5 g/kg), or vehicle, 5 min prior to bupropion dosing. The presence or absence of seizures, the number of seizures, the onset, duration and the intensity of seizures were all recorded for 5 h following the administration of ethanol.

RESULTS

The results show that administration of IP bupropion HCl alone induced seizures in mice in a dose-dependent manner, with the 120 mg/kg dose having the largest effect. The percentage of convulsing mice were 0%, 20%, 30% and 60% in the 0 (vehicle), 100, 110, and 120 mg/kg dose groups, respectively. Pretreatment with ethanol produced a larger bupropion HCl-induced convulsive effect at all the doses (70% each at 100, 110 and 120 mg/kg) and a 10% effect in the ethanol + vehicle only group. The convulsive dose of bupropion HCl required to induce seizures in 50% of mice (CD50), was 116.72 mg/kg for bupropion HCl alone (CI: 107.95, 126.20) and 89.40 mg/kg for ethanol/bupropion HCl (CI: 64.92, 123.10).

CONCLUSION

These results show that in mice alcohol lowers the seizure threshold for bupropion-induced seizures. Clinical implications are firstly that there may be an increased risk of seizures in patients consuming alcohol, and secondly that formulations that can release bupropion more readily in alcohol may present additional risks to patients.

Serotonin uptake blockers and voluntary alcohol consumption. A review of recent studies

Previous research demonstrated that serotonin uptake blockers (e.g., zimeldine, sertraline, fluoxetine) reduce voluntary ethanol consumption in rats and humans. However, the mechanism of action of these compounds is not well understood. It has been suggested, for example, that serotonin uptake blockade interferes with the processes that mediate the reinforcement derived from ethanol ingestion. On the other hand, there is considerable experimental evidence that suggests that the effects on alcohol intake may be an expression of a more general inhibitory role that serotonin plays in consummatory behavior. This chapter presents evidence that suggests that serotonin uptake blockers may affect ethanol intake, in part via a reduction of food intake. Current issues concerning the central versus peripheral mediation of these effects, receptor specificity, as well as alternate mechanisms of action are considered.

Medical management of the depressed alcoholic patient

Since the advent of modern psychopharmacology in the 1950s, use of medications in the treatment of many psychiatric disorders has become commonplace. Alcohol use is also widespread. As alcohol can interact with a wide variety of medications to alter drug effects, understanding the interactions between it and psychiatric medicines is important to the efficacious treatment of the depressed alcoholic with these drugs. This article briefly outlines the effects of alcohol and the mechanisms of its interactions with psychiatric medications. The most commonly used classes of psychiatric medicines, including antidepressants, CNS depressants, benzodiazepines, antipsychotics, psychostimulants, and lithium carbonate, are reviewed as to their potential interactions with alcohol. Clinical implications of these interactions are discussed.

The effects of tricyclic and 'atypical' antidepressants on spontaneous locomotor activity in rodents

With the exception of amineptin, buproprion and nomifensine all tricyclic and 'atypical' antidepressants have been reported to reduce spontaneous motor activity in rodents, after both acute and chronic administration. However, with the diversity of chemical actions of these drugs it is unlikely that a single neurochemical mechanism is underlying this one behavioral effect. These widespread sedative effects have implications for interpreting behavioral changes in other test situations, since sedation generally occurs at doses that fall within the dose-range effective in other tests. We also review the effects on spontaneous motor activity of withdrawal from chronic antidepressant treatment.

Zimeldine: a review of its effects on ethanol consumption

This review evaluates the literature and describes an extensive series of experiments which examined the effects of zimeldine , its metabolite norzimeldine and other serotonin and norepinephrine reuptake inhibitors on voluntary ethanol consumption in rats. The results of these experiments indicate that drugs which specifically inhibit serotonin reuptake are capable of decreasing voluntary ethanol consumption. The behavioral mechanism through which these drugs exert their effects seems to be extinction of the primary reinforcing properties of alcohol. These effects seem to be partially attenuated both by drugs which modulate the norepinephrine system as well as by the serotonin postsynaptic receptor blocker methergoline. The data presented in this review are discussed in terms of the involvement of the serotonin and norepinephrine systems in the mechanism of action of these drugs. In addition, several alternative hypotheses concerning the nature of the phenomenon are offered. Finally, the implications of these data for the possible development of a treatment procedure for problem drinkers is discussed.

Influence of alaproclate on antipyrine metabolite formation in man

Alaproclate, a selective serotonin reuptake inhibitor, presently undergoing clinical trial for the treatment of major depressive disorders, has been shown to inhibit hexobarbital metabolism in mice. In the present study the influence of oral alaproclate on the total plasma clearance of antipyrine and on the formation of its metabolites was investigated in 10 healthy volunteers. The peak level of alaproclate was reached after about 1.5 h, and after a distribution phase, its plasma elimination half-life was between 3.0 and 3.5 h. Antipyrine tests were performed before treatment, during the first four doses and after the seventh dose of alaproclate 200 mg/day. During treatment, total plasma antipyrine clearance and the clearance for production of all antipyrine metabolites were reduced by 30%, indicating non-selective inhibition of oxidative drug-metabolizing enzyme activity in man by alaproclate. After the last dose of alaproclate, antipyrine plasma clearance and the clearance to its metabolites returned to control values. In order to allow more detailed evaluation of the results, the time course of the clearances for production of metabolites was investigated. This revealed that the extent of inhibition of metabolite formation by alaproclate was dependent on the plasma alaproclate level, indicating a rapidly reversible inhibition.

Effects of zimeldine, mianserin and amitriptyline on psychomotor skills and their interaction with ethanol a placebo controlled cross-over study

13 healthy volunteers participated in a double-blind, four-period, cross-over study. In each period, the trial drugs (placebo, zimeldine, amitriptyline and mianserin) were given in fixed dosages for 8 days; amitriptyline 10-50 mg twice daily, mianserin 10-30 mg twice daily and zimeldine 200 mg once daily. Ethanol 1 g/kg bodyweight was drunk 2 hours after drug intake on Days 1 and 8 of each period, the latter being separated by a 2 week wash-out period. Ratings of subjective feelings and side effects, and performance tests were done on Days 1 and 8 of each period before, 1.5, 3 and 4.5 h after drug intake, i.e. 2 of the tests were performed under the influence of ethanol. Mianserin decreased critical flicker frequency, slowed reactions under discriminative stimulation and tended to cause nystagmus, but only on Day 1 (after the first 10 mg dose). Amitriptyline impaired coordination on Days 1 (after the initial 10 mg dose) and 8, and lowered the flicker threshold on Day 8 at "steady state" (after the 50 mg morning dose). Both these antidepressants were felt to be sedative, especially in the initial phase of the treatment, and they interacted additively with ethanol. No impairment of psychomotor skills was associated with zimeldine, only a subjective sedative effect of the 200 mg dose was seen on Day 1. Zimeldine did not enhance the effects of ethanol; it even showed some antagonism of ethanol-induced body sway in the standing steadiness test. In contrast to amitriptyline and mianserin, zimeldine was regarded as not harming psychomotor skills, and as not having any observable interaction with ethanol.

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.

Sedative/anxiolytic effects of antidepressants in animals

The sedative effects of several different structural types of antidepressants were investigated in mice. Six different models of sedation were used and the results were averaged. The rank order of sedative potency was: amitriptyline greater than mianserin greater than maprotiline greater than imipramine greater than desipramine greater than clomipramine greater than alaproclate greater than zimelidine greater than norzimelidine. Sedative potency of the antidepressants was found to be significantly correlated with their affinity for four different brain amine receptors. The rank order of correlation of sedation with receptor affinity was: histamine (H1) greater than serotonergic greater than muscarinic greater than alpha 1-adrenergic. These findings appear to be associated with clinical side effects observed during treatment with antidepressants. While scant literature is available concerning specific anxiolytic effects of antidepressants, pharmacological evidence for the role of central 5-HT systems in the anxiolytic effect is plentiful. Our preliminary findings show a marked antagonism of isolation-induced aggression by low doses of the specific 5-HT uptake inhibitor, zimelidine, and the 5-HT releasing agent, p-chloramphetamine, thus supporting the hypothetical importance of 5-HT in the pharmacology of anxiolytic agents.

The pharmacology of zimelidine: a 5-HT selective reuptake inhibitor

Zimelidine (ZIM) and its main active metabolite norzimelidine (NZIM) have been shown to preferentially inhibit 5-hydroxytryptamine (5-HT) neuronal uptake both in vitro and in vivo while having much less effect on noradrenaline (NA) uptake. ZIM in vivo blocked the 5-HT uptake mechanism in the cerebral cortex, hippocampus, striatum, hypothalamus and spinal cord, thus indicating effects on both the ascending and descending 5-HT pathways. ZIM is devoid of a 5-HT releasing action, MAO-inhibitory properties and effects on dopamine (DA) uptake. ZIM failed to reduce NA turnover even in high doses, but markedly reduced 5-HT turnover in very low doses in the rat. ZIM also enhanced 5-HT mediated behaviours in mice in doses related to the inhibition of 5-HT uptake. In contrast to amitriptyline (AMI) and mianserin (MIAN), ZIM only in extremely high doses displayed a 5-HT receptor blocking action in vitro and failed to block 5-HT mediated behaviour. ZIM was practically devoid of action on histamine H1 and H2 receptors, and had also a neglible action on noradrenergic alpha 1- and alpha 2-receptors, and on beta-receptors. Unlike the tricyclic antidepressants (TAD's) ZIM had a negligible action on muscarinic receptors and failed to affect cholinergic induced activity. Long-term treatment with ZIM did not result in any attenuation of the 5-HT uptake blocking potency or the reduction of 5-HT turnover. This long-term treatment slightly reduced the number of beta-receptors in the brain. However, repeated ZIM-treatment induced a new 5-HT receptor binding site characterized by a low affinity and with a high number of binding sites and decreased the number of high affinity 5-HT receptor binding sites. Unlike the TAD's zimelidine failed to block the action of reserpine. Metabolic and behavioural interactions studies in mice showed that ZIM was devoid of any significant interactions with ethanol, barbiturates and benzodiazepines. It is concluded that ZIM markedly differs from both the TAD's and new antidepressants such as mianserin and nomifensine. ZIM seems preferentially to effect the presynaptic 5-HT reuptake mechanism while having a negligible action on noradrenergic, 5-HT, acetylcholine and histamine receptors in the brain.