- Tranylcypromine and fenelzine are irreversible MAO inhibitors for MAO-A and MAO-B. Fenelzine has higher affinity for MAO-A, whereas tranylcypromine has higher affinity for MAO-B. Side effects could occur during a switch. Known side effect for tranylcypromine are sleeping problems, agitation and orthostatic hypotension. Known side effects in fenelzine are oedema and/or increased liver enzyme levels. In addition, monitoring of sodium levels is adviced.[1]