Potentiated CNS depressant effects w/ CNS depression-producing medications. Adrenergic crisis, collapse, coma, dizziness, excitation HTN, hyperpyrexia, intracerebral bleeding, lethargy, nausea, psychotic behavior, spasm & tremors w/ MAOIs eg, furazolidone, phenelzine, procarbazine, selegiline, tranylcypromine. Increased dextromethorphan serum conc w/ amiodarone, fluoxetine, quinidine. Increased serotonergic effects w/ sibutramine.