GUWS Medical

Antidepressants MAOI group

MAOIs (monoamine oxidase inhibitors) increase brain concentrations of monoamine neurotransmitters by inhibiting the enzymes concerned in their breakdown. They are effective for depression, anxiety, and phobic states, and sometimes achieve dramatic responses in patients who have failed to respond to tricyclics.

They may have a particular place in so-called atypical depression 'with reversed biological features, e.g. increased sleep, increased appetite, mood reactivity, and rejection sensitivity' (Butler et al., 2006). The BNF recommends that 'MAOIs should be tried in any patients who are refractory to treatment with other anti-depressants as there is occasionally a dramatic response' (http://www.bnf.org/ bnf/bnf/51/3341.htm?q=%22maois%22), although this advice is, sadly, seldom followed in practice.

In addition to their anticholinergic side-effects (similar to those described above for the tricyclics), MAOIs may cause potentially dangerous interactions with sympathomimetic drugs (including common-cold remedies) and tyramine-containing foods (Box 23.5), which must therefore be avoided. Such interactions produce headache and palpitations; rarely, they can produce a hypertensive crisis that may lead to stroke or sudden death. In order to do so, however, the departure from the advice above must be very gross and repeated. A single indiscretion would usually not produce any adverse effect.

Patients on MAOIs should be given a card listing the items to avoid. It is probable that the risks have been overestimated, and that these effective drugs have been underused as a result. The most recently introduced MAOI, moclobe-mide, is less prone to cause food and drug interactions because it is selective for the MAO-A isoform, which is found in the liver as opposed to the gut. It can be used on a trial basis: patients who respond somewhat to it can then be tried on a 'proper', full-strength MAOI.

Box 23.5 Interactions with MAOI

Foods Cheese (strong), red wine (especially Chianti), beer (strong), game, yeast, smoked fish, Marmite, Bovril. Drugs SSRIs, amphetamines, L-dopa, fenfluramine, local anaesthetics, ephedrine, triptans

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