Moclobemide and clomipramine in the treatment of depression. A randomized clinical trial

Atypical depression: a comprehensive review

Despite several decades of research, the characteristics distinguishing atypical depression from other depressive subtypes remain ambiguous. Multiple lines of evidence support the designation of atypical depression as a scientifically and clinically relevant subtype, including differences in hormonal responses, brain laterality, psychological profile and psychiatric co-morbidity and differential treatment response. The evolution of the diagnostic criteria for atypical depression has led to the designation of mood reactivity as the cardinal feature, and the research supporting this conclusion is reviewed. This paper also reviews the evidence for the drug treatment of atypical depression, with a particular focus on research related to the superior efficacy of monoamine oxidase inhibitors (MAOIs) compared with tricyclic antidepressants (TCAs). Data relevant to the efficacy of newer antidepressants, including selective serotonin reuptake inhibitors (SSRIs), serotonin-noradrenaline (norepinephrine) reuptake inhibitors, transdermal selegiline and other new agents for atypical depression, are discussed. In summary, the diagnostic reliability and validity of atypical depression still remain elusive and open to further evolution. Currently available findings suggest that atypical depression has preferential response to MAOIs over TCAs. More data are required to determine the efficacy of newer agents relative to MAOIs and TCAs, although limited studies have shown a non-inferior efficacy and better tolerability of newer agents such as SSRIs compared with those of MAOIs and TCAs. Finally, future directions for research include further refinement of the diagnostic criteria for atypical depression, and clarification of the role of newer antidepressants in the treatment of this subtype with evidence from randomized, controlled trials.

MAO inhibitors: pharmacodynamic aspects and clinical implications

Many recent studies have stressed the importance of maintaining the MAO inhibitors in the therapeutic arsenal for depressive patients. In most cases MAO inhibitors are generally safe and as well tolerated as the cyclic antidepressants. It has been suggested that MAO inhibitors are more likely to benefit depressed patients with atypical vegetative symptoms like gain in weight, sleep or libido. However, they may be therapeutic for a wide spectrum of psychiatric disorders ranging from depression with generalized anxiety or phobia, hysteroid dysphoria and endogenous affective illness refractory to conventional therapies. Because of the hazards: drug-drug and drug-food interactions, the irreversible and unspecific MAO inhibitors are only to be recommended on the condition that a good patient compliance can be obtained.

Treatment of depression with atypical features: a meta-analytic approach

The present meta-analysis addressed the empirical evidence regarding the treatment of major depression with atypical features. The superiority of monoamine oxidase inhibitors (MAOIs) compared with other antidepressants in the treatment of major depression with atypical features has been frequently reported. According to the CONSORT Statement, studies included in our meta-analysis had to meet several criteria, especially a double-blind, controlled condition and an operational diagnosis according to Diagnostic and Statistical Manual of Mental Disorders (DSM)-III or DSM-IV criteria, respectively. Four databases for research-based evidence were used in a systematic review: Medline, Embase, Psyndex and PsycInfo. Only eight publications met inclusion/exclusion criteria, resulting in 11 comparisons. Our results contrast an effect size of 0.45 (95% confidence interval) for a comparison of MAOIs vs. placebo with an effect size of 0.02 (95% confidence interval: - 0.10-0.14) for a comparison of MAOIs vs. selective serotonin reuptake inhibitors. The effect size for MAOIs vs. tricyclic antidepressants was 0.27 (95% confidence interval: 0.16-0.42). MAOIs may be more effective for atypical major depressive disorder than tricyclic antidepressants. Most clinical research has been conducted on irreversible MAOIs. Additional studies testing more recently developed antidepressants (including reversible MAOIs) with an improved safety profile would be warranted. The available data are insufficient for a direct comparison between MAOIs and selective serotonin reuptake inhibitors.

Comparison of the efficacy and safety of moclobemide and imipramine in the treatment of depression in Indian patients

BACKGROUND

Moclobemide, a benzamide, is one of the new-generation monoamine oxidase-A inhibitors (MAO-AIs) which belongs to the class of reversible inhibitors of monoamine oxidase (RIMA). Numerous studies have shown that moclobemide is well-tolerated and as effective as other antidepressants. So far, there is no evidence available regarding its efficacy and tolerability in India.

AIM

To compare the efficacy and safety of moclobemide with that of imipramine, a tricyclic antidepressant, in the treatment of major depressive disorder.

METHODS

In this prospective study, patients (n=60) were randomly assigned to treatment with moclobemide or imipramine for 6 weeks. Efficacy of the drugs was assessed by observing the mean change in scores on the Hamilton Depression Rating Scale (HDRS) and the Montgomery-Asberg Depression Scale (MADRS).

RESULTS

Both the groups showed significant decrease in scores at the end of 6 weeks. Patients who received moclobemide had a better side-effect profile.

CONCLUSION

Moclobemide is an effective antidepressant and is better tolerated than imipramine.

Orthostatic side effects of clomipramine and moclobemide during treatment for depression

From a clinical point of view, orthostatic hypotension is a significant side effect during antidepressant treatment, particularly in the case of tricyclic antidepressants (TCAs). This prospective, randomized clinical trial evaluated the effects of clomipramine and moclobemide on orthostatic blood pressure during treatment for depression. One hundred and fifteen depressed inpatients, age up to 70 years, were randomized to treatment with either moclobemide (400 mg/day) or clomipramine (150 mg/day) after 1 week of placebo treatment. Orthostatic blood pressure was measured weekly over the 6-week study period. Clomipramine, but not moclobemide, caused a statistically significant fall in systolic (F = 9.37, P = 0.0037) and diastolic orthostatic blood pressure (F = 3.74, P = 0.0017). In the clomipramine-treated group of patients, we found no correlation between subjective complaints of orthostatic dizziness and the size of systolic orthostatic blood pressure. In conclusion, this study indicates that moclobemide does not induce orthostatic side effects, which is a significant problem in treatment with TCAs. However, the choice of antidepressants depends on other factors as well, e.g. the therapeutic efficacy.

Moclobemide: therapeutic use and clinical studies

Moclobemide is a reversible inhibitor of monoamine-oxidase-A (RIMA) and has been extensively evaluated in the treatment of a wide spectrum of depressive disorders and less extensively studied in anxiety disorders. Nearly all meta-analyses and most comparative studies indicated that in the acute management of depression this drug is more efficacious than placebo and as efficacious as tricyclic (or some heterocyclic) antidepressants or selective serotonin reuptake inhibitors (SSRIs). There is a growing evidence that moclobemide is not inferior to other antidepressants in the treatment of subtypes of depression, such as dysthymia, endogenous (unipolar and bipolar), reactive, atypical, agitated, and retarded depression as with other antidepressants limited evidence suggests that moclobemide has consistent long-term efficacy. However, more controlled studies addressing this issue are needed. For patients with bipolar depression the risk of developing mania seems to be not higher with moclobemide than with other antidepressants. The effective therapeutic dose range for moclobemide in most acute phase trials was 300 to 600 mg, divided in 2 to 3 doses. While one controlled trial and one long-term open-label study found moclobemide to be efficacious in social phobia, three controlled trials subsequently revealed either no effect or less robust effects with the tendency of higher doses (600 - 900 mg/d) to be more efficacious. Two comparative trials demonstrated moclobemide to be as efficacious as fluoxetine or clomipramine in patients suffering from panic disorder. Placebo-controlled trials in this indication are, however, still lacking. A relationship between the plasma concentration of moclobemide and its therapeutic efficacy is not apparent but a positive correlation with adverse events has been found. Dizziness, nausea and insomnia occurred more frequently on moclobemide than on placebo. Due to negligible anticholinergic and antihistaminic actions, moclobemide has been better tolerated than tri- or heterocyclic antidepressants. Gastrointestinal side effects and, especially, sexual dysfunction were much less frequent with moclobemide than with SSRIs. Unlike irreversible MAO-inhibitors, moclobemide has a negligible propensity to induce hypertensive crisis after ingestion of tyramine-rich food ("cheese-reaction"). Therefore, dietary restrictions are not as strict. However, with moclobemide doses above 900 mg/d the risk of interaction with ingested tyramine might become clinically relevant. After multiple dosing the oral bioavailability of moclobemide reaches almost 100%. At therapeutic doses, moclobemide lacks significant negative effects on psychomotor performance, cognitive function or cardiovascular system. Due to the relative freedom from these side effects, moclobemide is particularly attractive in the treatment of elderly patients. Moclobemide is a substrate of CYP2C19. Although it acts as an inhibitor of CYP1A2, CYP2C19, and CYP2D6, relatively few clinically important drug interactions involving moclobemide have been reported. It is relatively safe even in overdose. The drug has a short plasma elimination half-life that allows switching to an alternative agent within 24 h. Since it is well tolerated, therapeutic doses can often be reached rapidly upon onset of treatment. Steady-state plasma levels are reached approximately at one week following dose adjustment. Patients with renal dysfunction require no dose reduction in contrast to patients with severe hepatic impairment. Cases of refractory depression might improve with a combination of moclobemide with other antidepressants, such as clomipramine or a SSRI. Since this combination has rarely been associated with a potentially lethal serotonin syndrome, it requires lower entry doses, a slower dose titration and a more careful monitoring of patients. Combination therapy with moclobemide and other serotonergic agents, or opioids, should be undertaken with caution, although no serious adverse events have been published with therapeutic doses of moclobemide to date. On the basis of animal data the combined use of moclobemide with pethidine or dextropropoxyphene should be avoided. There is no evidence that moclobemide would increase body weight or produce seizures. Some preclinical data suggest that moclobemide may have anticonvulsant property.

Dimensional assessment of onset of action of antidepressants: a comparative study of moclobemide vs. clomipramine in depressed patients with blunted affect and psychomotor retardation

The onset of action (during the first 2 weeks of treatment) of moclobemide (450 mg/day), a reversible MAO-A inhibitor, was compared in a double-blind, multi-center trial with clomipramine (150 mg/day) on dimensional and global depressive symptoms in 124 hospitalized patients suffering from a major depressive episode according to DSM-III-R criteria and with blunted affect and retardation. An earlier efficacy was found for moclobemide with significant treatment differences in favor of moclobemide, which were detected on negative symptoms (anhedonia, blunted affect and retardation) on days 7 and 10. The overall effect on depression at the end of the 4-week trial period was similar in both groups. However, a higher termination rate due to lack of efficacy was found with moclobemide (10 vs. 3). The tolerability was significantly better for moclobemide, as shown by the lower frequency of adverse events.

A guide to the safety of CNS-active agents during breastfeeding

For most agents with CNS activity, there are limited data regarding their safety in breastfeeding. Any decision to institute treatment for a neurological or psychiatric disorder must weigh the benefits of maternal treatment against the potential harm to the breastfeeding mother of withholding medication which may improve her illness. For the neonate, one must balance the risk of medication exposure against the benefit of receiving breast milk. Most tricyclic antidepressants can be used in lactating women. Because of the limited data, selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors should only be used with due consideration of the potential adverse effects. Breastfeeding is best avoided by women who require lithium therapy, because of both the immature excretory systems in the infant and relatively high doses received by the infant. There is little information about the safety of antipsychotic medications in breastfeeding. Concerns include toxicity and abnormal neurological development in the infant. These agents may be used with caution. Most agents which cause depression of the CNS, including opiates and sedatives, can be used in small doses and for short courses in breastfeeding mothers. Most anticonvulsants can be used in lactating women. Reference texts and consultation with experts are useful adjuncts to discussion of the risks and benefits of therapy with the patient. The scope of this review is limited to drugs with therapeutic uses, thus drugs of abuse are not discussed, nor are caffeine and alcohol (ethanol).

Synthesis, conformational analysis and antidepressant activity of moclobemide new analogues

Three new analogues of moclobemide are synthesized. Antidepressant activity of compounds assayed by the Porsolt method reveals that the morpholine ring in moclobemide is one of the key structural parts necessary for antidepressant activity. Superimposition of norepinephrine and gauche forms of serotonin and mociobemide suggest that the phenyl ring, electronegative group attached to the aromatic ring and the amine terminal group may serve as the recognition elements for binding to monoamine oxidase-A (MAO-A).

Moclobemide versus clomipramine in nonmelancholic, nonpsychotic major depression. A Study group

The efficacy and the safety of moclobemide (400-600 mg/day), a reversible and selective inhibitor of monoamine oxidase-A (RIMA) and of clomipramine (100-150 mg/day) were compared respectively in 98 and 93 nonmelancholic, nonpsychotic out-patients with a DSM-III major depressive episode over 6 weeks and up to 3 months, in a multi-center double-blind trial. No statistically significant difference between the treatments was found on the number of responders, at 6 weeks and 3 months, to the Hamilton Depression Rating Scale (HDRS), which was the main criterion for efficacy. The sample size was sufficient to detect a difference of approximatively 20% in response rates. Reduction of the total scores on HDRS and Covi anxiety scale was comparable for both treatments, but the reduction on the Retardation Depressive Scale (RDS) was significantly higher with moclobemide at the 1- and 2-week assessments. According to the RDS as well as the global impression of both patient and physician, a somewhat earlier onset of antidepressant action was evident in the moclobemide group. Tolerance was significantly better in the moclobemide group, mainly due to a lower frequency of weight gain, sedation and anticholinergic effects.

Moclobemide and nortriptyline in elderly depressed patients. A randomized, multicentre trial against placebo

Moclobemide and nortriptyline were compared with placebo in a double-blind randomized multinational (Canada, Denmark and UK) trial comprising 109 patients of > 60 years of age with major depression (DSM-III-R). Patients were randomized to 7 weeks of treatment with doses of 400 mg/day moclobemide, 75 mg/day nortriptyline or placebo. It was necessary to adjust nortriptyline dosage in < 20% of patients to maintain serum levels within the postulated therapeutic window of 50-170 ng/ml. At end of treatment, the remission rates were 23% for moclobemide, 33% for nortriptyline and 11% for placebo. Anticholinergic and orthostatic events occurred more often with patients on nortriptyline than either moclobemide or placebo.

Clinical, endocrine and neurochemical effects of moclobemide in depressed patients

The clinical efficacy of the monoamine oxidase A inhibitor moclobemide and its effect on the dexamethasone suppression test (DST) and plasma and urine methoxyhydroxyphenylglycol (MHPG) were investigated in 26 depressed patients during a 4-week clinical trial. Fourteen patients (54%) responded favourably to the treatment (50% or more reduction of the Hamilton Rating Scale for Depression score). All (8) patients with an abnormal DST responded to treatment; 11 of 16 patients with a normal DST did not respond. Patients with low pretreatment MHPG excretion, according to the median value, were more frequently treatment responders. Plasma and urine MHPG were significantly decreased by treatment. The results indicate that low excretion of MHPG and cortisol nonsuppression may be considered as predictors of favourable clinical response to moclobemide treatment.

Influence of food on the tyramine pressor effect during chronic moclobemide treatment of healthy volunteers

An open study was carried out to examine the effect of moclobemide, a new antidepressant reversible inhibitor of MAO-A, on the pressor response induced by oral tyramine added to meals of different lipid and protein composition, and to correlate the blood pressure increase in the tyramine test with that obtained during an exercise test. Eight healthy volunteers of both sexes participated in the study. A tyramine sensitivity and an exercise test were performed beforehand. Subjects were included if, under fasting condition, their systolic blood pressure (SBP) increased by more than 30 mmHg after administration of 400 or 600 mg tyramine. Exercise tests were performed to determine the grade of effort that corresponded to a rise in SBP of 30 mmHg. Subjects received moclobemide 600 mg/d. Starting on Day 7, each subject consumed a standardized meal (52 g lipids, 43 g proteins, 86 g carbohydrates) just before taking moclobemide. Tyramine was added to these meals in daily increasing doses of 50, 100, 150...mg until an increase in SBP > or = 30 mmHg was obtained. On moclobemide treatment, an average dose of 250 mg tyramine (range 150-400 mg) increased SBP by 36.6 mmHg. The time to reach peak SBP was longer (175 min) than in the fasting condition before the trial (40.6 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacotherapy of social phobia. A controlled study with moclobemide and phenelzine

In a double-blind, parallel group trial, 78 subjects with social phobia received moclobemide (a new reversible inhibitor of monoamine oxidase A) phenelzine, or placebo. After eight weeks, both active drugs-phenelzine somewhat more than moclobemide--were clinically and statistically significantly more effective than placebo, as assessed by rating scales. There was some further improvement between weeks 8 and 16, particularly in the moclobemide group; at week 16, 82% of the moclobemide and 91% of the phenelzine-treated patients were almost asymptomatic. Moclobemide was, however, much better tolerated than phenelzine. Patients withdrawn from active drugs had relapsed by week 24, providing additional support for the efficacy of the active drugs.

Moclobemide versus clomipramine in endogenous depression. A double-blind randomised clinical trial

The effects of moclobemide (300-600 mg/day), a reversible monoamine oxidase inhibitor - A (MAOI-A), were compared in a double-blind, multi-centre trial with those of clomipramine (100-200 mg/day) on 129 in-patients suffering from endogenous depression (according to ICD-9 and the Newcastle Scale). No significant differences in efficacy were seen between the two treatment groups. In the moclobemide group the mean scores on the MADRS were 36.4 on day 0 and 13.2 on day 42 (end-point analysis); scores were 37.4 and 10.9 respectively in the clomipramine group. An earlier onset of antidepressant activity was noted for moclobemide. Tolerability was significantly better for moclobemide, as shown by the Clinical Global Impression of Tolerance (CGIT). Anticholinergic effects, weight gain and orthostatic hypotension were more frequent in the clomipramine group. No biological treatment-related changes were observed.

The new generation of monoamine oxidase inhibitors

Irreversible and unspecific inhibitors of MAO were the first modern antidepressants, but after an initial success they fell into discredit due to adverse side effects. In the past two decades interest in MAO inhibitors has been renewed because of progress in basic research, a milestone being the finding that there are two subtypes of MAO, MAO-A and MAO-B. These are distinct proteins with high amino acid homology, coded by separate genes both located on the short arm of the human chromosome X. The enzyme subforms show different substrate specificities in vitro and different distributions within the central nervous system and in peripheral organs. In the central nervous system of man MAO-A seems to be mainly involved in the metabolism of 5 HT and noradrenaline, whereas 2-phenylethylamine and probably dopamine are predominantly deaminated by MAO-B. In the intestinal tract tyramine is mainly metabolized by MAO-A. These characteristics indicate distinct physiological functions of the two MAO-subforms. Several irreversible and reversible non-hydrazine inhibitors with relative selectivities for one of the MAO-subforms have been developed. They belong to various chemical classes with different modes of enzyme inhibition. These range from covalent mechanism based interaction (e.g. by propargyl- and allylamine derivatives) to pseudosubstrate inhibition (e.g. by 2-aminoethyl-carboxamides) and non-covalent interaction (e.g. by brofaromine, toloxatone and possibly moclobemide). The most important pharmacological effects of the new types of MAO inhibitors are those observed in neuropsychiatric disorders. The inhibitors of MAO-A show a favorable action in various forms of mental depression. The drugs seem to have about the same activity as other types of antidepressants, including tricyclic and related compounds as well as classical MAO inhibitors. The onset of action of the MAO-A inhibitors is claimed to be relatively fast. Other possible indications of these drugs include disorders with cognitive impairment, e.g. dementia of the Alzheimer type. In subjects with Parkinson's disease the MAO-B inhibitor L-deprenyl exerts a L-dopa-sparing effect, prolongs L-dopa action and seems to have a favorable influence regarding on-off disabilities. The action is in general transitory (months to several years). In addition L-deprenyl has been shown to delay the necessity for L-dopa treatment in patients with early parkinsonism. Whether the drug influence the progression of the disease is still a matter of debate. L-deprenyl also appears to have some antidepressant effect (especially in higher doses) and to exert a beneficial influence in other disorders, e.g. dementia of the Alzheimer type.(ABSTRACT TRUNCATED AT 400 WORDS)

Moclobemide in depression: a randomized, multicentre trial against isocarboxazide and clomipramine emphasizing atypical depression

Moclobemide was compared with isocarboxazide and clomipramine in patients with depression. A total of 167 outpatients were allocated to daily treatment with 300 mg moclobemide, 30 mg isocarboxazide or 150 mg clomipramine for 6 weeks. Moclobemide was slightly inferior to clomipramine, whereas isocarboxazide had an intermediate position. There was no interaction between treatment and atypical or nonatypical depression. Anticholinergic symptoms and orthostatic hypotension were most pronounced in the clomipramine group.

Comparison of the monoamine oxidase inhibiting properties of two reversible and selective monoamine oxidase-A inhibitors moclobemide and toloxatone, and assessment of their effect on psychometric performance in healthy subjects

1. The effects of two reversible, predominantly monoamine oxidase-A (MAO-A) inhibitors, moclobemide (150 mg three times daily) and toloxatone (400-200-400 mg day-1) on monoamine metabolites and psychometric performance were compared in a double-blind placebo controlled crossover study in 12 healthy subjects. 2. After 7 days of moclobemide/toloxatone/placebo administration subjects were hospitalized for 24 h on day 8. Blood samples were drawn every 2 h for determination of plasma noradrenaline (NA), 3,4-dihydroxyphenylglycol (DHPG), homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5-HIAA). Urine was collected for measurements of normetanephrine and 3-methoxytyramine excretion. Psychometric performance (short- and long-term memory, critical flicker fusion frequency, choice reaction time) and subjective feelings were assessed before each drug intake (in the morning, at noon, in the evening). 3. Compared with placebo, both reversible monoamine oxidase inhibitors decreased the plasma concentration of DHPG and HVA. The overall fall in DHPG (AUC from 0 to 24 h) was 44% during moclobemide and 12% during toloxatone (P less than 0.001) and the overall decrease in HVA was 38% and 20% (P less than 0.005) on moclobemide and toloxatone, respectively. 4. Before the next drug intake, MAO-A inhibition, as judged by the decrease of plasma DHPG concentration, was significantly different from placebo with moclobemide but not with toloxatone. 5. Moclobemide, but not toloxatone, exerted a moderate, but significant inhibition of the deamination of 5-hydroxytryptamine (5-HT) as judged by the fall in plasma 5-HIAA concentration. Neither drug influenced plasma NA concentration. 6. A significant rise in urinary excretion of normetanephrine was observed on moclobemide and to a lesser extent on toloxatone. The urinary excretion of 3-methoxytyramine was significantly raised by moclobemide but not by toloxatone. 7. Neither moclobemide nor toloxatone altered memory function, vigilance, subjective feelings or sleep characteristics of the subjects.

The effects of moclobemide on nocturnal sleep of depressed patients

The effect of moclobemide, a short-acting, reversible, preferential type-A MAO inhibitor (300 mg daily in three divided doses), on the sleep of eight depressed patients was assessed by polysomnographic recordings in a 4-week therapeutic trial. Six patients showed an improvement greater than 50% on the Hamilton Depression Rating Scale. Compared to placebo, patients receiving moclobemide showed improved sleep continuity as judged by the decrease in wake time after sleep onset and total wake time, particularly during the intermediate and late stages of drug administration. Total sleep time increase was comprised of larger amounts of stage 2 NREM sleep. REM sleep latency was significantly increased and REM sleep % decreased during the drug administration period. However, in contrast to the older, non-selective and selective MAOIs, moclobemide had a mild REM sleep suppressant effect.

Tolerability of moclobemide, a new reversible inhibitor of monoamine oxidase-A, compared with other antidepressants and placebo

Moclobemide, a new selective and reversible inhibitor of monoamine oxidase A (RIMA), has been compared with various tricyclic antidepressants (TCAs) in numerous controlled studies. Pooled data from these studies, comprising 1656 patients, as well as the consideration of individual trials, show that moclobemide is far better tolerated than the TCAs. Its side effects mainly comprise mild degrees of nausea and dizziness at the beginning of treatment in a small proportion of patients. Age and sex do not affect the tolerability of moclobemide: it is equally well tolerated by elderly patients. In 2300 patients treated with moclobemide in doses up to 600 mg/day, without dietary restrictions, there was no tyramine-related hypertensive reaction. It is concluded that moclobemide may be the second-generation antidepressant doctors were waiting for--equally effective as the classical antidepressants but far better tolerated.

Reversible and irreversible monoamine oxidase inhibitors in other psychiatric disorders

In addition to being effective in depressive disorders, monoamine oxidase inhibitors (MAOIs) have been shown to be effective in controlled studies of patient with panic disorder with agoraphobia, social phobia, atypical depression or mixed anxiety and depression, bulimia, posttraumatic stress disorder (PTSD) and borderline personality disorder. Uncontrolled case reports have noted MAOI efficacy in obsessive-compulsive disorder (OCD), trichotillomania, dysmorphophobia and avoidant personality disorder. Reversible inhibitors of MAO-A (RIMAs) appear safer than the classical irreversible MAOIs since they have less potential to increase blood pressure. They have not been studied as yet, however, in most of the conditions responsive to MAOIs. If RIMAs are found effective in these disorders, they would probably achieve wider use than MAOIs because they are safer and tend to cause fewer side effects.

Disposition kinetics of moclobemide, a new MAO-A inhibitor, in subjects with impaired renal function

A single intravenous and oral dose of moclobemide (Ro 11-1163) was administered to 13 subjects with varying degrees of renal impairment (creatinine clearances ranging from 0 to 40 mL/min). The resulting disposition and absorption parameters of moclobemide were more variable than but, with the exception of mean absorption time, were not significantly different from values obtained in another study conducted in 12 normal healthy subjects. There were no relationships between any of the disposition parameters and renal function as measured by creatinine clearance. The disposition of two metabolites of moclobemide were partially characterized from plasma data. One of these (Ro 12-8095) appears to be formation rate-limited and, from available data, behaves in a manner similar to what has been observed in normals. The other metabolite (Ro 12-5637) has a long apparent disposition half-life and is present in greater concentrations in the renally impaired compared to the normal subjects. The latter observation may reflect reduced elimination clearance in the renally impaired subjects. Based upon the results of this study there does not appear to be any need to alter the normal dosing regimen of moclobemide in subjects with renal impairment in order to achieve drug concentrations similar to those in healthy subjects.

What has happened to the new antidepressant drugs?

Depression is a widespread and serious disease for which a multiplicity of antidepressant drugs is available for treatment. Although these agents are numerous, there is little to distinguish among them except for their different side-effects. This article reviews the antidepressant drugs that currently are available in Australia, the antidepressant drugs that are used in other countries and some antidepressant drugs that are likely to become available internationally in the next few years.

Moclobemide, an inhibitor of MAO-A, does not increase daytime plasma melatonin levels in normal humans

1. Plasma melatonin concentrations were determined after administration of single oral doses (100, 200 and 300 mg) of moclobemide, a reversible inhibitor of monoamine oxidase (MAO) with predominant effects on the A-type of the enzyme, to eight young, healthy male volunteers in a double-blind, random-order, placebo-controlled study. The investigation was later continued in an open fashion by giving a single 10 mg dose of the MAO-B inhibitor deprenyl to the same subjects. 2. Neither drug had any effects on plasma melatonin levels, in spite of very marked MAO-A inhibition after moclobemide (as evidenced by up to 79% average decreases in the plasma concentrations of 3,4-dihydroxyphenylglycol, a deaminated metabolite of noradrenaline) and over 90% inhibition of MAO-B activity in blood platelets after deprenyl. 3. It is concluded that daytime human plasma melatonin levels do not accurately reflect MAO-A inhibition in acute drug studies.

Moclobemide excretion in human breast milk

1. Six lactating white women, aged 24-36 years, received a single oral dose of 300 mg moclobemide, between 09.00 h and 11.00 h, 3 to 5 days after the delivery of a full term neonate. 2. Complete milk collections were obtained before, 3, 6, 9, 12 and 24 h after drug administration by means of a breast pump. Venous blood samples were drawn before, and 0.5, 1, 3, 4.5, 6, 9, 12, 24 h post-dosing. 3. Moclobemide, and its major metabolite (Ro 12-8095) were measured in milk and plasma samples using h.p.l.c. The active metabolite (Ro 12-5637) could only be detected in plasma. 4. Moclobemide and its metabolites were not detectable in 24 h plasma samples. Cmax, tmax and t1/2 for moclobemide were (mean +/- s.d.) 2.70 +/- 1.24 mg l-1, 2.03 +/- 1.19 h and 2.26 +/- 0.26 h, respectively. 5. The concentrations of moclobemide and Ro 12-8095 in milk were highest at 3 h after drug administration and the drug and metabolite were not detectable after 12 h. Ro 12-5637 was not detected in any milk sample. The percentages of the dose excreted as moclobemide and Ro 12-8095 were (mean +/- s.d.) 0.057 +/- 0.020% and 0.031 +/- 0.011%, respectively. An average 3.5 kg breast-fed neonate would therefore be exposed to only a 0.05 mg kg-1 moclobemide dose (approximately 1% of the maternal dose on the mg kg-1 basis). The low amount of moclobemide excreted into breast milk is unlikely to be hazardous to suckling infants.

Evidence that the reversible MAO-A inhibitor moclobemide increases prolactin secretion by a serotonergic mechanism in healthy male volunteers

The serotonin receptor antagonist methysergide was used to investigate the mechanism mediating stimulation of prolactin release after single doses of the reversible MAO-A inhibitor moclobemide. Eight healthy male volunteers participated in a placebo-controlled cross-over study, where pretreatment with methysergide almost totally prevented the moclobemide-induced increase in plasma prolactin levels. MAO-A inhibition, as evidenced by up to 80% decreases in the plasma concentration of 3,4-dihydroxyphenylglycol, a deaminated metabolite of norepinephrine, was similar after both pretreatments. This result suggests that moclobemide stimulates prolactin release through activation of serotonergic receptors, and provides evidence that the drug is capable of augmenting central serotonergic neurotransmission in humans.

Is diazepam an antidepressant?

In double-blind sequential study, diazepam was compared with the proven antidepressant moclobemide, in patients with atypical depression. Both agents significantly improved depression ratings over eight weeks of treatment. Diazepam was a significantly better antidepressant than moclobemide at four week, although not at eight weeks. All patients ceased diazepam within one year and none reported withdrawal reactions. These data suggest the need to reconsider that benzodiazepines may be antidepressants and to study their possible antidepressant actions.

Moclobemide and clomipramine in reactive depression. A placebo-controlled randomized clinical trial

The purpose of this study was to compare moclobemide and clomipramine in reactive depression according to the Newcastle II classification. Sixty patients were allocated to either 300 mg moclobemide, 150 mg clomipramine or placebo, all divided in 3 daily doses. Improvements occurred over time, but differences between treatments and compared with placebo were never statistically significant. Dizziness, tremor and anticholinergic symptoms were significantly more frequent with clomipramine than with moclobemide and placebo.

Moclobemide and clomipramine in endogenous depression. A randomized clinical trial

The purpose of this study was to compare moclobemide and clomipramine in endogenous depression according to the Newcastle II classification. Sixty-two patients were allocated to either 300 mg moclobemide or 150 mg clomipramine, both given in 3 daily doses. Improvements occurred over time but differences between treatments were never statistically significant. Dizziness, tremor and anticholinergic symptoms were significantly more frequent with clomipramine.

Monoamine oxidase inhibitors: rehabilitation from recent research?

For a long time, monoamine oxidase inhibitors (MAOIs) have been the Cinderella drugs of psycho-pharmacy. Although they were introduced just before the tricyclic antidepressants (TCAs), they rapidly became second-line treatments. Several factors contributed to this, in particular the dietary restrictions, the scattered reports of death from overdose and/or toxic interactions, and the unfavourable reports on the efficacy of phenelzine in depression from, among others, the Medical Research Council trial (1965). For a number of years afterwards, prescription of these drugs was limited to a few enthusiasts. More recently, however, their popularity has increased owing firstly to a re-evaluation of their effectiveness in tricyclic-resistant depression and in anxiety disorders, and secondly to growing awareness of the exaggerated claims made about their dangerousness (Pare, 1985).

A sequential double-blind controlled study of moclobemide and diazepam in patients with atypical depression

A double-blind controlled study comparing moclobemide and diazepam in patients with atypical depression was carried out. Statistical comparison of the 14 pairs completing 4 weeks showed that significant reductions in depressive symptomatology as measured by the Hamilton and Carroll depression rating scales occurred in both drug groups, and that diazepam was significantly better than moclobemide. A separate analysis of the 10 pairs completing 8 weeks treatment showed that significant decreases in depression ratings occurred in both drug groups but that by week 8 there was no significant difference between the two drugs for depression scores. Side-effects were minimal, and the most common side-effects emerging for both drugs were sleep disturbance and physical tiredness.

Inhibition of monoamine oxidase by moclobemide: effects on monoamine metabolism and secretion of anterior pituitary hormones and cortisol in healthy volunteers

1. Single oral doses (100, 200 and 300 mg) of moclobemide, a reversible inhibitor of monoamine oxidase (MAO) with predominant effects on the A-type of the enzyme, were administered to eight young, healthy male volunteers in a double-blind, random-order, placebo-controlled study. The investigation was thereafter continued in an open fashion by administering a single 10 mg dose of the MAO-B inhibitor deprenyl to the same subjects. 2. Deamination of catecholamines was powerfully and dose-dependently inhibited by moclobemide, as evidenced by up to 40% decreases in the urinary excretion of deaminated catecholamine metabolites, corresponding increases in the excretion of non-deaminated, methylated metabolites, and up to 79% average decreases in the plasma concentration of 3,4-dihydroxyphenylglycol (DHPG), a deaminated metabolite of noradrenaline (NA), and up to 75% average decreases in the plasma concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC), a deaminated metabolite of dopamine. The urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA) was only slightly reduced. In contrast, deprenyl, in a dose which almost totally inhibited MAO-B activity in blood platelets, did not appreciably affect the plasma concentrations of DHPG or DOPAC. 3. Due to the rapid, reversible, dose-dependent and MAO-A specific effect of moclobemide on plasma concentrations of DHPG, it is suggested that DHPG in plasma may be a useful indicator of the magnitude and duration of MAO-A inhibition in man. 4. Sympatho-adrenal function at rest was not significantly altered by moclobemide, as judged by unchanged plasma catecholamine concentrations and stable blood pressure and heart rate recordings. 5. Monoamine oxidase type B activity in blood platelets was slightly (less than 30%) and transiently inhibited after moclobemide. 6. The secretion of prolactin was dose-dependently stimulated by moclobemide, whereas the plasma concentrations of growth hormone (hGH) and cortisol remained unchanged.

Tranylcypromine in depression resistant to cyclic antidepressions

1. Non-responders to cyclic antidepressants were treated with the MAO-inhibitor tranylcypromine in two studies: the first study in an open comparison with L-5-hydroxytryptophan (L-5HTP), the second study in a double blind comparison with nomifensine. 2. While both L-5HTP and nomifensine appeared to be ineffective, tranylcypromine was effective in 26 out of 45 patients. 3. It is concluded that besides ECT also MAO-inhibitors such as tranylcypromine are an effective alternative for depressed patients not responding to cyclic antidepressants.

Tyramine pressor response with moclobemide--a reversible monoamine oxidase inhibitor

Moclobemide is a reversible, short-acting monoamine oxidase inhibitor (MAO1), specific for MAO A. To study moclobemide effects on the tyramine pressor response, we gave 12 depressed patients (2 males, 10 females; mean age 47, SD 11 years) an i.v. tyramine test after 7 days drug free. The mean (+/- SD) tyramine dose to raise systolic blood pressure 30 mmHg was 5.6 +/- 2.5 mg. Repeat tyramine testing after 2 weeks of treatment with moclobemide (280 +/- 90 mg/d) showed the tyramine dose required was reduced to 2.5 +/- 1.6 mg (n = 8). The mean (+/- SD) increase in sensitivity to tyramine was 2.9 +/- 1.8. Four patients did not have repeated tyramine tests as testing was discontinued because of tyramine-induced cardiac arrhythmias. Moclobemide seems an effective antidepressant with less tyramine sensitivity than MAOIs in current use.

MAO inhibitors in mental disease: their current status

Available MAOIs seem to be mainly indicated for the heterogeneous group of patients with depressive syndromes. Although groups of patients with all the recognized major subtypes of depression (including "endogenous depression") probably respond in varying degrees, MAOIs appear to be particularly indicated for out-patients with "neurotic depression" complicated by panic disorder or hysteroid dysphoria, which involves repeated episodes of depressed mood in response to feeling rejected. MAOIs can also be effective in several anxiety syndromes, in particular panic disorder. Other reports have claimed success in a variety of other syndromes including bulimia, anorexia nervosa, obsessive-compulsive neurosis, atypical facial pain and some other types of chronic pain, childhood attention deficit disorder and delusions of infestation by parasites. The nature of any underlying personality disorder is an important response variable and the assessment of personality should be encouraged in further studies. The development of new drugs raises the prospect of a range of MAOIs targeted at specific patient populations. Tranylcypromine also merits further investigation as clinical experience suggests that it can produce a dramatic response in some patients with phenelzine-resistant disorders. This may be due, at least in part, to its amphetamine-like effects.