PSEUDO-PHEOCHROMOCYTOMA 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 tomo graphic scan and much higher plasma noradrenaline than adrenaline conc entrations. Urinary vanillylmandelic acid concentrations were only mod erately elevated. This syndrome probably arose as a consequence of an interaction between the monoamine oxidase inhibitor selegiline, the sy mpathomimetic agent ephedrine, and a tricyclic antidepressant. The mec hanism of the interaction is thought to be related to increased sympat hetic release of noradrenaline by ephedrine, inhibition of catabolism by selegiline, and inhibition of reuptake of noradrenaline by the tric yclic. Although newer selective monoamine oxidase inhibitors are consi dered to be safer than earlier non-selective inhibitors, they can also contribute to drug interactions mimicking phaeochromocytoma.