Fluoxetine-induced bradycardia and syncope in two patients.

Fluoxetine appears to cause a low incidence of adverse cardiac effects. An uncommon but potentially hazardous effect of fluoxetine therapy, however, is bradycardia accompanied by faintness or syncope. The authors report two cases in which this adverse effect occurred. They hypothesize that the mechanism of bradycardia in these cases represents a direct central nervous system effect of increased serotonin on medullary cardiovascular regulation.