Trazodone can lower the seizure threshold. Patients may require increased concentrations of anticonvulsants to achieve equivalent effects if trazodone is added. Trazodone metabolism can be inhibited by cimetidine or ranitidine, resulting in increased plasma levels of trazodone that could lead to toxicity. Patients should be closely observed for toxic effects such as orthostatic hypotension or sedation. Trazodone may have an increased risk of causing toxicity if used with oral contraceptives, fluoxetine, erythromycin, or methylphenidate because of the inhibition of hepatic metabolism.
Priapism occasionally results in permanent impairment of erectile function or impotence.
Patients should be warned of the possibility and to discontinue the drug at once and consult with the physician if this reaction occurs. Careful consideration should be given before administering the drug to postpubescent male patients. Hypotension, including orthostatic hypotension, can occur during therapy with trazodone and is dose-related. Patients taking antihypertensive drugs may require a reduction in the dosage. Cardiac arrhythmias, eg. ventricular tachycardia, are not as common during therapy with trazodone as with tricyclic antidepressants, but they have occurred in patients with or without preexisting cardiac disease.