Risk-benefit assessment of newer versus older monoamine oxidase (MAO) inhibitors

The first generation of monoamine oxidase (MAO) inhibitors fell into disuse because of poor efficacy in major depression with melancholia and/or endogenous depression, and because of poor tolerability (drug interactions and the 'cheese' effect). New MAO inhibitors, reversible inhibitors of MAO-A (RIMAs), are able to induce a reversible and specific inhibition of MAO-A. Consequently, the inhibition of MAO is quicker and the dose-response relationship improved, such that dosage adjustment is easier. Also, no carry-over effect once treatment is terminated is observed. The frequency and severity of drug interactions with RIMAs is reduced, although coadministration with pethidine (meperidine) or dextromethorphan should still be avoided. No specific subgroup of patients with depression has shown a better or worse response to RIMAs. The presence of melancholia in major depression, or the existence of endogenous depression, are not predictive of reduced efficacy compared with tricyclic antidepressant (TCA) reference compounds. Dysthymic patients have shown a good response to both RIMAs and TCAs independent of the co-existence of a major depressive episode. Older MAO inhibitors are more effective than TCAs in the treatment of atypical depression, and further studies are needed to confirm if this is true for RIMAs. Long term studies to evaluate the effects of RIMAs on disease recurrence are also required. RIMAs are better tolerated than older MAO inhibitors, including use in subgroups particularly at risk of adverse effects such as the elderly. Overall, RIMAs appear to represent therapeutic progress in the treatment of depression in terms of both efficacy and tolerability.