Like other monoamine oxidase inhibitors, Isocarboxazid potentiates the action of a number of drugs and foods. Patients being treated with a monoamine oxidase inhibitor should not receive indirectly-acting sympathomimetic agents such as amphetamines, metaraminol, fenfluramine or similar anorectic agents, ephedrine or phenylpropanolamine (contained in many proprietary 'cold-cure' medications), dopamine or levodopa. Patients should also be warned to avoid foodstuffs and beverages with a high tyramine content: mature cheeses (including processed cheeses), hydrolysed yeast or meat extracts, alcoholic beverages, particularly heavy red wines such as Chianti, non-alcoholic beers, lagers and wines, and other foods which are not fresh and are fermented, pickled, 'hung', 'matured' or otherwise subject to protein degradation before consumption. Broad bean pods (which contain levodopa) and banana skins may also present a hazard. In extreme cases interactions may result in severe hypertensive episodes. Isocarboxazid should therefore be discontinued immediately upon the occurrence of palpitations or frequent headaches.
Pethidine should not be given to patients receiving monoamine oxidase inhibitors as serious, potentially fatal reactions, including central excitation, muscle rigidity, hyperpyrexia, circulatory collapse, respiratory depression and coma, can result. Such reactions are less likely with morphine, but experience of the interaction of Isocarboxazid with narcotic analgesics other than pethidine is limited and extreme caution is therefore necessary when administering morphine to patients undergoing therapy with Isocarboxazid.
Isocarboxazid should not be administered together with other monoamine oxidase inhibitors, selective serotonin reuptake inhibitors (SSRIs) or most tricyclic antidepressants (clomipramine, desipramine, imipramine, butriptyline, nortriptyline or protriptyline). Although there is no proof that combined therapy will be effective, refractory cases of depression may be treated with Isocarboxazid in combination with amitriptyline or trimipramine, provided appropriate care is taken. Hypotensive and other adverse reactions are likely to be increased.
An interval of 1 - 2 weeks should be allowed after treatment with Isocarboxazid before the administration of antidepressants with a different mode of action or any other drug which may interact. A similar interval is recommended before administration of Isocarboxazid when another antidepressant has been used; in the case of drugs with a very long half-life (such as fluoxetine), it may be advisable to extend this interval.
Isocarboxazid should be discontinued for at least 2 weeks prior to elective surgery requiring general anaesthesia. The anaesthetist should be warned that a patient is being treated with Isocarboxazid, in the event of emergency surgery being necessary. Concurrent administration of Isocarboxazid with other central nervous system depressants (especially barbiturates and phenothiazines), stimulants, local anaesthetics, ganglion-blocking agents and other hypotensives (including methyl-dopa and reserpine), diuretics, vasopressors, anticholinergic drugs and hypoglycaemic agents may lead to potentiation of their effects. This should be borne in mind if dentistry, surgery or a change in treatment of a patient becomes necessary during treatment with Isocarboxazid.
All patients taking Isocarboxazid should be warned against self-medication with proprietary 'cold-cure' preparations and nasal decongestants and advised of the dietary restrictions listed under 'warnings'.
With Isocarboxazid, as with other drugs acting on the central nervous system, patients should be instructed to avoid alcohol while under treatment, since the individual response cannot be foreseen.