GUANETHIDINE AND TRICYCLICS

The antihypertensive effects of guanethidine are reduced or abolished by amitripty- line, desipramine, imipramine, nortriptyline and protriptyline. Doxepin in doses of 300 mg or more daily interacts similarly, but in smaller doses appears not to do so, although one case is reported with doxepin 100 mg daily.
Not every combination of guanethidine and a tricyclic antidepressant has been studied but all are expected to interact similarly. Concurrent use should be avoided unless the effects are very closely monitored and the interaction balanced by raising the dosage of the antihypertensive.