The present status of monoamine oxidase inhibitors

[70-year history of studying the effectiveness of therapy of patients with depression with antidepressants - irreversible nonselective monoamine oxidase inhibitors]

The history of studying the effectiveness of therapy of patients with depression by irreversible non-selective monoamine oxidase inhibitors (MAOIs) is analyzed and systematized. Authors describe the stages of the appearance of the first data on the effectiveness of treatment by the first representatives (the 50^s of the XX century), the targeted study of the effectiveness of the use of numerous «new» representatives and the emergence of disagreements in assessing the power of therapy (the end of the 50^s-60^s of the XX century), continuing to study the effectiveness of treatment by representatives who remained in clinical practice, and establishing its clinical predictors (80^s-90^s of the XX century), the appearance of the first data on the effectiveness of therapy for «atypical depression» (1959-1960) and further development of this issue (80^s-90^s of the XX century). The stage of formation and development of the idea of the effectiveness of treatment for resistant depression (late 70^s-90^s of the XX century) is characterized. Separately, the history of studying the effectiveness of application in the USSR and Russia (late 50^s- 90^s of the XX century) is outlined. The current state of the issue of assessing the effectiveness of therapy (the end of the 90^s of the XX century - 2022) is shown.

Evolution of ideas about the risk of tyramine syndrome developing during therapy with irreversible non-selective monoamine oxidase inhibitors (to the 70th anniversary of the first use of this group of antidepressants)

We describe the history of studying of the problem of tyramine syndrome during the treatment with antidepressants, irreversible non-selective monoamine oxidase inhibitors. Data on clinical observations are presented. Early hypotheses of pathogenesis are considered. The period of discovery of the relationship between increased blood pressure and the use of foods containing tyramine is outlined. The transformation of terminology is demonstrated. The events associated with the restriction of the use of therapy are characterized. The formation of the opinion about the exaggeration of the risk of developing tyramine syndrome is analyzed. Data on the involvement in the discussion of the problem of tyramine syndrome of society as a whole are given. 

Monoamine Oxidase Inhibitors (MAOIs) in Psychiatric Practice: How to Use them Safely and Effectively

Monoamine oxidase inhibitors (MAOIs) were among the first licensed pharmacological treatments for patients with depression but over time have fallen out of mainstream clinical use. This has led to a loss of clinician training opportunities and reduced availability of MAOIs for prescribing. This article provides a concise and practical overview of how to use MAOIs safely and effectively in psychiatric practice. We consider the history of MAOIs, why they are not used more frequently, their mechanisms of action, availability, indications and efficacy, general tolerability, withdrawal symptoms, and safety considerations (including hypertensive reactions and serotonin syndrome). Practical advice is given in terms of dietary restrictions, interactions with other medications (both prescribed and non-prescribed), and how prescribers can stop and switch MAOIs, both within the drug class and outside of it. We also provide advice on choice of MAOI and treatment sequencing. Lastly, we consider emerging directions and potential additional indications.

New 2-Pyrazoline and Hydrazone Derivatives as Potent and Selective Monoamine Oxidase A Inhibitors

Thirty compounds having 1-[2-(5-substituted-2-benzoxazolinone-3-yl) acetyl]-3,5-disubstitutedphenyl-2-pyrazoline structure and nine compounds having N'-(1,3-disubstitutedphenylallylidene)-2-(5-substituted-2-benzoxazolinone-3-yl)acetohydrazide skeleton were synthesized and evaluated as monoamine oxidase (MAO) inhibitors. All of the compounds exhibited selective MAO-A inhibitor activity in the nanomolar or low micromolar range. The results of the molecular docking for hydrazone derivatives supported the in vitro results. Five compounds, 6 (0.008 μM, Selectivity Index (SI): 9.70 × 10^-4), 7 (0.009 μM, SI: 4.55 × 10^-5), 14 (0.001 μM, SI: 8.00 × 10^-4), 21 (0.009 μM, SI: 1.37 × 10^-5), and 42 (0.010 μM, SI: 5.40 × 10^-6), exhibiting the highest inhibition and selectivity toward hMAO-A and nontoxic to hepatocytes were assessed for antidepressant activity as acute and subchronic in mice. All of these five compounds showed significant antidepressant activity with subchronic administration consistent with the increase in the brain serotonin levels and the compounds crossed the blood-brain barrier according to parallel artificial membrane permeation assay. Compounds 14, 21, and 42 exhibited an ex vivo MAO-A profile, which is highly consistent with the in vitro data.

Antidepressive effects of the selective MAO-inhibitor brofaromine:an open trial

In an open prospective study, the antidepressive effects of the selective and reversible MAO-A inhibitor, brofaromine, were investigated in nine endogenous depressed patients, who had failed to respond to cyclic antidepressants. In three patients a clinically relevant improvement was observed, although for the total group, no statistically significant treatment effect could be demonstrated. In two subjects, postural hypotension and sleep disturbances occurred temporarily.

Tranylcypromine in mind (Part II): Review of clinical pharmacology and meta-analysis of controlled studies in depression

It has been over 50 years since a review has focused exclusively on the monoamine oxidase (MAO) inhibitor tranylcypromine (TCP). A new review has therefore been conducted for TCP in two parts which are written to be read preferably in close conjunction: part I - pharmacodynamics, pharmacokinetics, drug interactions, toxicology; and part II - clinical studies with meta-analysis of controlled studies in depression, practice of TCP treatment, place in therapy. The irreversible and nonselective MAO-A/B inhibitor TCP has been confirmed as an efficacious and safe antidepressant drug. For the first time, a meta-analysis of controlled clinical trials in depression demonstrated that TCP is superior to placebo (pooled logOR=0.509, 95%CI=0.026 to 0.993, 4 studies) and equal to other antidepressants (pooled logOR=0.208, 95%CI=-0.128 to 0.544, 10 studies). In treatment resistant depression (TRD) after tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs), TCP was superior to placebo (logOR=2.826, 95%CI=1.494 to 4.158, one study) and non-established antidepressants (pooled logOR=1.976, 95%CI=0.907 to 3.045, 4 studies), and was equal to other MAO inhibitors and an antidepressant combination (pooled logOR=-0.366, 95%CI=-0.869 to 0.137, 4 studies). Controlled studies revealed that TCP might provide a special advantage in the treatment of atypical depression, which was supported by a recent PET study of MAO-A activity in brain. However, TCP treatment remains beset with the need for a mandatory tyramine-restricted diet and is therefore limited to use as a third-line antidepressant according to recent treatment algorithms and guidelines for depression treatment. On the other hand, the effort needed to maintain a tyramine-restricted diet may have been overestimated in the perception of both doctors and patients, which may have led to relative underuse of TCP. Interaction with serotonergic drugs bears the risk of severe serotonin toxicity (SST) and combination with indirect sympathomimetic drugs may result in hypertensive crisis which both adds to the risks of TCP. At the same time, TCP has low to no risks of central anticholinergic, sedative, cardiac conduction, body weight, hemostatic effects, or pharmacokinetic drug interactions. Neuroprotection by MAO inhibitors due to reduced oxidative stress is becoming increasingly studied. Taken together, TCP is being increasingly recognized as an important option in systematic treatment approaches for patients suffering from severe courses of depression, such as TRD and atypical depression, by offering a MAO-related pathophysiological rationale.

The effects of MAOA genotype, childhood trauma, and sex on trait and state-dependent aggression

Monoamine oxidase A (MAOA) genotypic variation has been associated with variation in aggression, especially in interaction with childhood trauma or other early adverse events. Male carriers of the low-expressing variant (MAOA-L) with childhood trauma or other early adverse events seem to be more aggressive, whereas female carriers with the high-expressing variant (MAOA-H) with childhood trauma or other early adverse events may be more aggressive. We further investigated the effects of MAOA genotype and its interaction with sex and childhood trauma or other early adverse events on aggression in a young adult sample. We hypothesized that the association between genotype, childhood trauma, and aggression would be different for men and women. We also explored whether this association is different for dispositional (trait) aggression versus aggression in the context of dysphoric mood. In all, 432 Western European students (332 women, 100 men; mean age 20.2) were genotyped for the MAOA gene. They completed measures of childhood trauma, state and trait measures of aggression-related behaviors (STAXI), and cognitive reactivity to sad mood (LEIDS-R), including aggression reactivity. Women with the MAOA-H had higher aggression reactivity scores than women with the MAOA-L. This effect was not observed in men, although the nonsignificant findings in men may be a result of low power. Effects on the STAXI were not observed, nor were there gene by environment interactions on any of the aggression measures. A protective effect of the low-expression variant in women on aggression reactivity is consistent with previous observations in adolescent girls. In females, the MAOA-H may predispose to aggression-related problems during sad mood.

Prediction of longer-term outcome of treatment-resistant depression in tertiary care

BACKGROUND

Systematic studies on the outcome of treatment-resistant depression are scarce.

AIMS

To describe the longer-term outcome and predictors of outcome in treatment-resistant depression.

METHOD

Out of 150 patients approached, 118 participants with confirmed treatment-resistant depression (unipolar, n = 77; bipolar, n = 27; secondary, n = 14) treated in a specialist in-patient centre were followed-up for between 8 and 84 months (mean = 39, s.d. = 22).

RESULTS

The majority of participants attained full remission (60.2%), most of whom (48.3% of total sample) showed sustained recovery (full remission for at least 6 months). A substantial minority had persistent subsyndromal depression (19.5%) or persistent depressive episode (20.3%). Diagnosis of bipolar treatment-resistant depression and poorer social support were associated with early relapse, whereas strong social support, higher educational status and milder level of treatment resistance measured with the Maudsley Staging Method were associated with achieving quicker remission. Exploratory analysis of treatment found positive associations between treatment with a monoamine oxidase inhibitor (MAOI) in unipolar treatment-resistant depression and attaining remission at discharge and at final follow-up, and duloxetine use predicted attainment of remission at final follow-up.

CONCLUSIONS

Although many patients with treatment-resistant depression experience persistent symptomatology even after intensive, specialist treatment, most can achieve remission. The choice of treatment and presence of good social support may affect remission rates, whereas those with low social support and a bipolar diathesis should be considered at higher risk of early relapse. We suggest that future work to improve the long-term outcome in this disabling form of depression might focus on social interventions to improve support, and the role of neglected pharmacological interventions such as MAOIs.

Kinetics of Inhibition of Monoamine Oxidase Using Cymbopogon martinii (Roxb.) Wats.: A Potential Antidepressant Herbal Ingredient with Antioxidant Activity

The study was designed to evaluate the antioxidant activity and effect of Cymbopogon martinii (Roxb.) Wats. (Poaceae) leaves on the activity of monoamine oxidase and kinetics of enzyme inhibition. Ethanol extract of C. martinii and rat brain mitochondrial monoamine oxidase preparation ware used to study the kinetics of enzyme inhibition using double reciprocal Lineweaver-Burk plot. The DPPH was used as a source of free radical to evaluate antioxidant potential. It is observed that, the ethanolic extract of C. martinii inhibits the monoamine oxidase activity with competitive mode of inhibition. The V(max) (0.01 mM/min) remained constant while, K(m) varied from 21.00 ± 1.1, 43.33 ± 1.5 and 83.33 ± 1.4 mM for 100-500 μg/ml concentration of C. martinii. The K(i) values were calculated to be 90.00 ± 0.87, 75.00 ± 0.69, 68.18 ± 0.68 μg for 100-500 μg/ml concentration of C. martini. It also shows a significant DPPH (1,1-diphenyl-2-picryl hydrazine) radical scavenging (IC(50) = 0.34 ± 0.05 mg/ml) and reducing activity (IC(50) = 0.70 ± 0.22 mg/ml). The C. martini can be considered as a possible source of MAO inhibitor used in the treatment of depression and other neurological disorders.

MAO-inhibitors in Parkinson's Disease

Monoamine oxidase inhibitors (MAO-I) belong to the earliest drugs tried in Parkinson's disease (PD). They have been used with or without levodopa (L-DOPA). Non-selective MAO-I due to their side-effect/adverse reaction profile, like tranylcypromine have limited use in the treatment of depression in PD, while selective, reversible MAO-A inhibitors are recommended due to their easier clinical handling. For the treatment of akinesia and motor fluctuations selective irreversible MAO-B inhibitors selegiline and rasagiline are recommended. They are safe and well tolerated at the recommended daily doses. Their main differences are related to (1) metabolism, (2) interaction with CYP-enzymes and (3) quantitative properties at the molecular biological/genetic level. Rasagiline is more potent in clinical practise and has a hypothesis driven more favourable side effect/adverse reaction profile due to its metabolism to aminoindan. Both selegiline and rasagiline have a neuroprotective and neurorestaurative potential. A head-to head clinical trial would be of utmost interest from both the clinical outcome and a hypothesis-driven point of view. Selegiline is available as tablet and melting tablet for PD and as transdermal selegiline for depression, while rasagiline is marketed as tablet for PD. In general, the clinical use of MAO-I nowadays is underestimated. There should be more efforts to evaluate their clinical potency as antidepressants and antidementive drugs in addition to the final proof of their disease-modifying potential. In line with this are recent innovative developments of MAO-I plus inhibition of acetylcholine esterase for Alzheimer's disease as well as combined MAO-I and iron chelation for PD.

The role of monoamine oxidase inhibitors in current psychiatric practice

The use of monoamine oxidase inhibitors (MAOIs) by psychiatrists has declined over the past several decades with the expansion of psychiatrists' pharmacologic armamentarium. This trend has also been driven by concern about food and drug interactions and side effects, as well as waning physician experience with these medications. Many psychiatrists, in fact, never prescribe MAOIs. Recent research has liberalized the MAOI diet and identified symptom presentations more likely to respond to these medications. Thus, clinicians must continue to familiarize themselves with the properties of and indications for prescribing MAOIs.

Australian and New Zealand clinical practice guidelines for the treatment of depression

BACKGROUND

The Royal Australian and New Zealand College of Psychiatrists (RANZCP) is co-ordinating the development of clinical practice guidelines (CPGs) in psychiatry, funded under the National Mental Health Strategy (Australia) and the New Zealand Ministry of Health.

METHOD

The CPG team reviewed the treatment outcome literature, consulted with practitioners and patients and conducted meta-analyses of outcome research.

TREATMENT RECOMMENDATIONS

Establish an effective therapeutic relationship; provide the patient with information about the condition, the rationale for treatment, the likelihood of a positive response and the expected timeframe; consider the patient's strengths, life stresses and supports. Treatment choice depends on the clinician's skills and the patient's circumstances and preferences, and should be guided but not determined by these guidelines. In moderately severe depression, all recognized antidepressants, cognitive behavioural therapy (CBT) and interpersonal psychotherapy (IPT) are equally effective; clinicians should consider treatment burdens as well as benefits, including side-effects and toxicity. In severe depression, antidepressant treatment should precede psychological therapy. For depression with psychosis, electroconvulsive therapy (ECT) or a tricyclic combined with an antipsychotic are equally helpful. Treatments for other subtypes are discussed. Caution is necessary in people on other medication or with medical conditions. If response to an adequate trial of a first-line treatment is poor, another evidence-based treatment should be used. Second opinions are useful. Depression has a high rate of recurrence and efforts to reduce this are crucial.

Interactions between psychotropics, anaesthetics and electroconvulsive therapy: implications for drug choice and patient management

Despite many predictions that electroconvulsive therapy (ECT) would be replaced by pharmacotherapy, ECT has remained an invaluable adjunct in the management of severe psychiatric disease. Both pharmacotherapy and ECT continue to be used extensively, and will frequently be administered concurrently. The majority of patients requiring ECT will need anaesthesia; therefore, interactions could conceivably occur between the psychotropic drugs, ECT and the anaesthetic agents utilised. In managing an anaesthetic for ECT the effects of the anaesthetic agents and other medications on seizure intensity are important determinants influencing outcome. With regard to the antidepressants, tricyclic antidepressants (TCAs) and ECT can be combined safely and beneficially. More care is required when ECT is administered in the setting of a monoamine oxidase inhibitor (MAOI), especially the older irreversible varieties and in patients recently placed on MAOI therapy. Of the anticonvulsants and mood stabilisers, lithium and ECT given concurrently add significant risk of delirium and/or organic syndromes developing. Possible concerns with valproate, carbamazepine, lamotrigine, gabapentin and topiramate are that they may inhibit seizure activity. Additionally, carbamazepine may prolong the action of suxamethonium (succinylcholine). The combination of antipsychotics and ECT is well tolerated, and may in fact be beneficial. As regards the anxiolytics, benzodiazepines have anticonvulsant properties that might interfere with the therapeutic efficacy of ECT. CNS stimulants on the other hand may prolong seizures as well as produce dysrhythmias and elevate blood pressure. Calcium channel antagonists should be used with great care to avoid significant cardiovascular depression. The anaesthesiologist should therefore remain vigilant at all times, as untoward responses during ECT might occur suddenly due to interactions between psychotropics, anaesthetic agents and/or ECT.

Monoamine oxidase inhibitors. An update on drug interactions

After initial enthusiasm, the use of monoamine oxidase inhibitors (MAOIs) has been limited by the wide range of MAOI-drug and MAOI-food interactions that are possible, particularly with sympathomimetic medications or tyramine-containing foods, resulting in hypertensive reactions. Despite their clinical benefits, this has led to a reduction in use of such medications. Discovery of the 2 main subgroups of monoamine oxidase, types A and B, led to the synthesis of MAOIs selective for one or other of these isoenzymes. Consequently, selegiline (deprenyl), a selective MAO-B inhibitor, was developed for the treatment of idiopathic Parkinson's disease. This drug is useful in the treatment of the early stages of the disease and later on as an adjunct to other drug therapies. Although the selective MAO-A inhibitor, clorgiline (clorgyline), was found to be effective in the treatment of depression, it still retained the potential to cause hypertensive reactions. Recently, agents that are not only selective, but reversible in their inhibition of MAO-A (RIMAs) have been synthesised (e.g. moclobemide and toloxatone), and have proven antidepressant efficacy. Whilst they are less likely to induce hypertensive reactions with the concomitant administration of sympathomimetic drugs or with tyramine-rich foodstuffs, it still seems wise to advocate care in co-prescribing potentially interacting medications and to advise a degree of caution with regard to the dietary intake of foodstuffs likely to contain a high tyramine content. Although these newer drugs represent an advance in safety, their use has, as yet, only been established in the treatment of depression. RIMAs also retain a potential for adverse interaction with other drugs. Concomitant prescription of serotonin-enhancing drugs should only be undertaken with caution for patients on moclobemide, toloxatone or selegiline. Coprescription of sympathomimetic drugs should also be avoided with these newer MAOIs and patients should be advised against purchasing over-the-counter preparations that may contain sympathomimetic drugs.

Pharmacodynamics and pharmacokinetics of two dose regimens of befloxatone, a new reversible and selective monoamine oxidase inhibitor, at steady state in healthy volunteers

The pharmacodynamic equipotency of 2 dose regimens (5 mg twice daily versus 10 mg once daily) of befloxatone, a new reversible and selective monoamine oxidase A (MAO-A) inhibitor, after single and multiple doses for 6 days was examined in a randomized, double-blind, three-way crossover, placebo-controlled trial of 12 healthy volunteers. Plasma levels of the deaminated metabolite 3-4 dihydroxyphenylglycol (DHPG), as measured by high-performance liquid chromatography (HPLC) with coulometric electrochemical detection, were used as an index of MAO inhibition. A single dose of befloxatone produced a significant dose-related reduction in plasma DHPG levels, as shown by the decrease in the 24-hour area under the concentration-time curve (AUC0-24) of DHPG, which peaked 2 hours after administration and persisted over 24 hours. Both dose regimens provided equipotent extent and duration of MAO-A inhibition at steady state, suggesting a once daily dosage should be sufficient for most patients. The pharmacokinetic bioavailability at steady state of both dose regimens was also similar. The concentration-time effect curve after a single dose revealed a hysteresis corresponding to the delay necessary to elicit MAO inhibition and/or elimination of DHPG. The relationship between plasma levels of DHPG and/or elimination of plasma concentrations of DHPG and befloxatone after a single dose can be modeled using the Emax model with a mean EC50 of 4.75 ng/mL, and suggests the presence of a maximal response from the single dose. This model permits prediction of steady-state levels of DHPG.

Pressor effect of oral tyramine during treatment with befloxatone, a new reversible monoamine oxidase-A inhibitor, in healthy subjects

The interaction between tyramine and befloxatone, a new selective, reversible monoamine oxidase-A (MAO-A) inhibitor, was studied in a single-blind, parallel-group study in 30 healthy male volunteers whose fasting tyramine 30 dose (Tyr30) was 400 or 600 mg. Each subject completed a placebo run-in period followed by a befloxatone period. Befloxatone was given in repeated doses according to one of three regimens: befloxatone 20 mg once daily at the end of a meal rich in tyramine or befloxatone 10 or 20 mg twice daily 2 hours before a meal rich in tyramine. Subjects were given increasing daily doses of tyramine mixed with the meal, until a systolic blood pressure increase of at least 30 mm Hg was achieved (Tyr30). The mean Tyr30 decreased from 1220 mg (range, 600-1800 mg) during placebo to 290 mg (range, 150-500 mg) during befloxatone 20 mg once daily, 250 mg (range, 100-300) during befloxatone 10 mg twice daily, and 155 mg (range, 100-250 mg) during befloxatone 20 mg twice daily; corresponding to a potentiation factor of 5.2-, 6.5-, and 7.9-fold, respectively. The extent and the duration of the systolic blood pressure increase did not significantly differ between the placebo and the befloxatone regimens, except for a longer duration with the 20-mg twice daily regimen. These results are similar to those reported with the therapeutic dosage of other selective MAO-A inhibitors. They suggest that there would be little risk of hypertensive crisis in patients treated in clinical studies with befloxatone, and thus dietary restrictions appear to be unnecessary when the drug is given in a regimen of up to 20-mg once daily after meals.

Pseudo-phaeochromocytoma after multiple drug interactions involving the selective monoamine oxidase inhibitor selegiline

A patient presented with paroxysmal hypertension and typical clinical features of phaeochromocytoma, but with a normal adrenal computed tomographic scan and much higher plasma noradrenaline than adrenaline concentrations. Urinary vanillylmandelic acid concentrations were only moderately elevated. This syndrome probably arose as a consequence of an interaction between the monoamine oxidase inhibitor selegiline, the sympathomimetic agent ephedrine, and a tricyclic antidepressant. The mechanism of the interaction is thought to be related to increased sympathetic release of noradrenaline by ephedrine, inhibition of catabolism by selegiline, and inhibition of reuptake of noradrenaline by the tricyclic. Although newer selective monoamine oxidase inhibitors are considered to be safer than earlier non-selective inhibitors, they can also contribute to drug interactions mimicking phaeochromocytoma.

Interaction of MAO inhibitors and dietary tyramine: a new experimental model in the conscious rat

The aim of this study was to assess a new model for tyramine-induced pressor effects in the rat. The predictivity of the test is improved by simulating the real clinical situations where tyramine is ingested with food and beverages containing the amine. The pressor effect was investigated after oral administration of tyramine in a feed preparation or in a water solution by continuously recording blood pressure just above the aorta junction via a left-carotid catheter. The response was quantified by measurement of peak systolic blood pressure and as the percentage of tyramine-sensitive rats (TSR) in which the maximal pressor response to the amine was higher than 30 mm Hg (clinical risk threshold). Tyramine elicited, after oral administration (by gavage), a statistically significant dose-dependent increase in blood pressure from the dose of 10 mg/kg in solution (i.e. 23 +/- 3 mm Hg, N = 36) and 40 mg/kg in feed preparation (i.e., 20 +/- 2 mm Hg, N = 26). Almost all rats showed a systolic blood pressor increase higher than 30 mm Hg after oral administration of tyramine at a dose of 80 mg/kg p.o. in solution (TSR = 96%). Administration of tyramine in food (80 mg/kg) significantly delayed the time of the peak blood pressure (13 +/- 2 min instead of 7 +/- 0.5 min in solution, p < .001). Under these conditions, the tyramine threshold dose of TYR 30 (dose inducing an average response equivalent to the clinical risk threshold) was 14 mg/kg p.o. in solution and 67 mg/kg p.o. in feed preparation, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Brofaromine in endogenous depression

1. Recently, a new generation of monoamine oxidase (MAO) inhibitors has been developed which selectively and reversibly inhibit MAO-A activity. 2. One of these compounds, called brofaromine, has been administered in subjects suffering from endogenous depression, revealing antidepressive efficacy in a majority of them without inducing serious adverse events. 3. The results obtained so far suggest that brofaromine might be effective in endogenous depressed patients who failed to respond to tricyclic antidepressants.

Spontaneous hypertensive reactions with monoamine oxidase inhibitors

Despite long-standing concerns over hypertensive reactions, monoamine oxidase inhibitors (MAOIs) have grown in popularity and are now used in a variety of psychiatric disorders. The risk of hypertensive episodes is less than 1%. This is most likely the result of careful dietary instructions and prudent prescribing of concomitant medications. The possibility exists of spontaneous or unprovoked hypertensive crises in patients receiving MAOIs. In this report, we review the literature on spontaneous hypertensive episodes and present a case report. There has been a total of 11 cases described in six separate reports. We discuss the possible mechanism, risk factors, treatment, and safety of rechallenging the patients with the MAOI. Further research is needed to clarify this reaction. For now, it remains a rare but worrisome phenomenon. It should stand as an additional source of concern for clinicians who are already well aware of the risk of hypertensive episodes in patients receiving MAOIs.

An Australian multicentre study of moclobemide versus amitriptyline in the treatment of depression

This paper reports the results of a multicentre study of the new monoamine oxidase inhibitor, moclobemide, in the treatment of major depression. Moclobemide is a specific monoamine oxidase-A inhibitor which does not bind irreversibly to the enzyme, unlike the currently available MAOIs. Recent studies would suggest that in subjects taking moclobemide blood pressure elevation caused by tyramine is significantly less than that induced by the irreversible MAOIs, particularly when tyramine is administered in an oral form. Forty-eight patients with major depression were randomly allocated to treatment with either moclobemide or amitriptyline for 4 weeks in a double-blind comparison. There were no statistically significant differences between the two groups on measures of efficacy. Patients taking amitriptyline reported a greater number of side-effects and more patients in the amitriptyline group dropped out because of these. There were no reports of interactions with tyramine-containing foods.

Liquid chromatographic estimation of tranylcypromine in human plasma

A simple, selective and quantitative estimation of tranylcypromine using liquid chromatography and electrochemical detection with apomorphine as internal standard in human plasma is described. Sample preparation is done by liquid-liquid extraction. The absolute mean recovery of apomorphine is 95%, the recovery of tranylcypromine is 81%. This method gives a simple estimation method to assay plasma concentrations of tranylcypromine in the therapeutic range (5-200 ng/ml) with good reproducibility and linearity.

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.

Antidepressants: uses and attitudes among consultant psychiatrists – A questionnaire study

An audit of Consultant Psychiatrists' views on and uses of antidepressant drugs is reported. At present senior prescribers largely opt for the older tricyclic antidepressants despite a knowledge of their shortcomings. MAOIs are less popular and newer drugs are viewed cautiously and apprehensively. Lofepramine is largely viewed as an alternative to dothiepin and amitriptyline. Non-drug strategies in the management of depression consist largely of support, environmental manipulation and electroconvulsive therapy. The relatively novel treatment, cognitive therapy, has a strong minority following.

Tolerability and antidepressive effect of brofaromine, a short-acting reversible MAO inhibitor--an open study

The tolerability and antidepressive effect of brofaromine, a selective MAO-A inhibitor was tested in 14 depressive patients. None of the patients showed blood pressure or pulse frequency changes after ingesting tyramine-enriched meals. Four instances of agitation were observed as side effects. In two of these cases, the appearance of paranoid thinking and suicidal tendencies led to premature termination of the study. In 3 cases sleep disturbances, in particular difficulties in falling asleep, were observed. In the test of antidepressive effectiveness (measured on the HAMD-scale) significant improvement was observed from day 14 onwards.

Are the monamine oxidase inhibitors facing extinction?

The use of monoamine oxidase inhibitors (MAOIs) in the province of Saskatchewan was compared for two years, 1978 and 1986, using the Saskatchewan Prescription Drug Plan data base. The percentage of the adult population receiving an MAOI decreased from 0.17% in 1978 to 0.07% in 1986. The use of both tricyclic antidepressants and the new generation antidepressants increased during the same period. Physicians appear to have selectively avoided using MAOIs for the elderly. Physicians who are not psychiatrists showed the greatest reduction in their use of the MAOIs. The data indicate an increasing reluctance to prescribe the MAOIs despite the recent resurgence of interest in these agents and the positive literature concerning their safety and efficacy.

Clinical pharmacology of moclobemide, a new reversible monoamine oxidase inhibitor

The clinical pharmacology of the new reversible monoamine oxidase (MAO) inhibitor, moclobemide, was examined in three separate studies in healthy male volunteers. In a single oral dose study, moclobemide (25-150 mg) was rapidly absorbed from the gastrointestinal tract and had a relatively short plasma half-life (mean 1.3 h after 150 mg). A decrease in the plasma concentrations of the noradrenaline metabolite 4- hydroxy-3-methoxyphenylglycol (HMPG), however, indicated a longer time to peak pharmacodynamic effect and longer duration of activity. Assay of platelet MAO activity did not reveal any evidence of irreversible inhibition of the B form of the isoenzyme. Single oral doses of moclobemide (150 and 300 mg) significantly lowered the threshold to the cardiovascular effects ('cheese reaction') of intravenous tyramine. However, after repeated administration of 100 mg three times daily for over 2 weeks, moclobemide caused significantly less potentiation than did phenelzine (15 mg three times per day) on the cardiovascular effects of oral tyramine, a clinically more relevant model. The MAO-B inhibitor, selegiline (5 mg once daily), also lowered the oral tyramine threshold significantly. Moclobemide was generally well tolerated by these healthy volunteers.

Current issues in monoamine oxidase inhibitor treatment

Interest in the monoamine oxidase (MAO) inhibitors has been revived over the past fifteen years since the publication of studies and reviews which argue their relative safety and efficacy in certain patient subgroups. The authors conclude that there is a continuing role for the MAO inhibitors in treating atypical depressive illness and panic disorders. Careful selection of patients to be commenced on MAO inhibitor treatment is advised. When prescribed alone or in combination with lithium there is evidence to support a usefulness for MAO inhibitors in depression resistant to the tricyclic antidepressants. Their efficacy in the depressed phase of bipolar affective disorder or in combination with the tricyclic antidepressants remains unproven. The risk of anaesthesia while a patient is receiving MAO inhibitor treatment may be less than heretofore believed. There is realistic hope of finding among the short-acting selective MAO inhibitors an effective antidepressant which is also free from tyramine related effects. With the increasing difficulties of evaluating new drugs on account of ethical and governmental constraints, it may however be some time before the preliminary hopeful findings can be substantiated in larger groups of patients.

Hypotensive action and weak potentiation of tyramine effect by moclobemide in rats

Moclobemide belongs to a new class of reversible, selective monoamine oxidase-A (MAO-A) inhibitors; it is clinically well tolerated and has little liability to potentiate tyramine pressor effects. Measurement of blood pressure and heart rate in conscious, freely moving rats showed only a slight, nonsignificant decrease in mean arterial pressure in normotensive animals. However, in spontaneously hypertensive rats, moclobemide significantly decreased blood pressure by 20 mmHg within 30 min of oral intake of 30 mg/kg. In the same animals, heart rate was decreased by 20%; normal values returned after 2-3 h. Tyramine alone in oral doses up to 15 mg/kg had no effect on blood pressure in normotensive rats, and after treatment with 30 mg/kg moclobemide, tyramine at 5 mg/kg did not alter mean arterial pressure, whereas there was a significant increase after doses of tranylcypromine, toloxatone and brofaromine. Higher doses of tyramine (10-20 mg/kg) following moclobemide led to a rise of 30-40 mmHg in pressure, but this had disappeared within 20 min. This effect was almost completely eliminated by desipramine, suggesting that coadministration of a norepinephrine uptake inhibitor with a reversible MAO inhibitor is likely to reduce the risk of tyramine-induced hypertensive crisis. Thus, the authors conclude that moclobemide exerts only a slight hypotensive action in hypertensive rats, and differs from other MAO inhibitors in potentiating the pressor effect of tyramine only weakly.

Some basic aspects of reversible inhibitors of monoamine oxidase-A

A novel class of antidepressants is emerging with considerable therapeutic potential: reversible inhibitors of monoamine oxidase type A (RIMA). Moclobemide (Aurorix) is a representative RIMA. It is a fully and rapidly reversible inhibitor of MAO-A with a correspondingly intermediate duration of action in vivo. It is free of hepatotoxicity and produces a much weaker potentiation of the tyramine pressor effect than the classical irreversible MAO inhibitors. Interaction of MAO inhibitors and monoamine reuptake inhibitors with tyramine is discussed on the basis of experiments in conscious rats. The issue of tyramine content of foods and beverages has been reinvestigated and its relevance for treatment with RIMA antidepressants is discussed. Recently observed antihypoxic (neuroprotective) effects of moclobemide suggest new indications for this compound.

Clinical, biochemical and psychometric findings with the new MAO-A-inhibitors moclobemide and brofaromine in patients with major depressive disorder

N = 53 inpatients with major depressive disorder have been treated with the reversible, selective MAO-A-inhibitors moclobemide (double-blind versus maprotiline) and brofaromine (open study), respectively. Clinically, significant improvement of depression and an activating profile of action could be observed, typical side effects were sleep disturbances, agitation and weight loss. The neurobiochemical data showed an increase of noradrenaline plasma concentrations under treatment with moclobemide. Visual reaction times improved with antidepressant treatment. MAO-A inhibitors proved to be effective antidepressants in the treatment of hospitalized patients with predominantly endogenous depressions.

The psychopharmacological era: notes toward a history

Cultural and economic influences on the psychopharmacological era are reviewed, in an attempt to bring into focus what has been happening in psychopharmacology for the past thirty years. It is argued that the belief that clinical advances are made through the heroic achievements of disinterested scientists is a simplistic view that may militate against future significant discoveries. Such discoveries, it is argued, still come about for the most part serendipitously, despite a widespread belief that psychopharmacology has become a rational science.

The pharmacology of human anxiety

The human pharmacology of anxiety disorders, including panic disorder, is detailed. The major theories center around the role of benzodiazepine receptor, noradrenergic and serotonergic dysfunction. The contribution that challenge tests with lactate, hyper- and hypocapnia, beta- and alpha-2-adrenoceptor agonists, peptides, pentylenetetrazol, and caffeine make to our understanding of the biological basis of anxiety and these major theories are described and discussed.

Efficacy of combined antidepressant therapy in resistant neurotic disorder

A 35-year-old woman with persistent affective and phobic symptoms responded dramatically to a combination of isocarboxazid and amitriptyline, and this improvement was maintained over the next three-and-a-half years. Isocarboxazid was replaced by placebo, using double-blind procedure. The change to placebo was accompanied by a marked increase in anxiety and depressive symptoms, which resolved when active isocarboxazid was reintroduced. It is suggested that combined antidepressant therapy still has a place in the treatment of resistant neurotic disorder.

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).

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.

Treatment strategy in depression. II. MAO inhibitors in depression resistant to cyclic antidepressants: two controlled crossover studies with tranylcypromine versus L-5-hydroxytryptophan and nomifensine

Antidepressants are ineffective in about 30% of the patients with major depression. Besides electroconvulsive therapy (ECT) and lithium, MAO inhibitors have been suggested as an alternative in such patients. In 2 controlled, partial crossover studies involving 47 patients with major depression who had already been treated unsuccessfully with at least 2 cyclic antidepressants, the effect of the MAO inhibitor tranylcypromine was studied. The first study was an open comparison with L-5-hydroxytryptophan (L-5HTP), the second study a double-blind comparison with nomifensine. Neither the patients treated with L-5HTP nor the patients treated with nomifensine, except one, improved. In contrast, tranylcypromine was effective in 50% of the patients. The depressions of the responders to tranylcypromine appeared to be more endogenous (according Newcastle Scale II) and of shorter duration than those of the non-responders. It is concluded that MAO inhibitors such as tranylcypromine are an effective alternative to ECT and lithium in patients with major depression who have failed to respond to cyclic antidepressants.