Catastrophic drug-drug interactions in psychopharmacology

Drug interactions may reflect pharmacokinetic processes, pharmacodynamic processes, or both. Some interactions are classified as idiosyncratic, as their mechanisms are not yet understood. Drug interactions involving psychotropic medications are ubiquitous; they typically result in changes in drug levels and/or drug effects. Fortunately, most drug interactions in psychiatry do not result in serious harm. Some drug interactions, however, are potentially catastrophic. The focus of this review is on the principal mechanisms of drug interactions and on potentially serious and life-threatening adverse consequences (eg, serotonin syndrome, hypertensive crises, arrhythmias, anticholinergic toxicity, seizures, dermatologic emergencies, bleeding, respiratory depression) of drug interactions in psychiatry. Patients with refractory psychiatric disorders, as well as medical comorbidity, often require treatment with complex drug regimens. The risk of catastrophic drug interactions involving psychotropic medications may be minimized by knowledge of the mechanisms of drug interactions and by familiarity with the rare, yet potentially life-threatening drug interactions that involve psychotropic medications.