Trimipramine Diltiazem

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Diltiazem and verapamil can increase plasma imipramine levels, possibly accompanied by undesirable ECG changes. Two isolated reports describe increased nortriptyline and trimipramine levels in two patients given diltiazem. 

A depressed woman taking trimipramine 125 mg daily developed high plasma levels of 546 micrograms/L while taking diltiazem 60 mg three times daily. Two weeks later they reached 708 micrograms/L, despite a reduction in the trimipramine dosage to 75 mg daily. She showed no toxicity and her ECG was normal. ... 

It has been suggested that diltiazem and verapamil increase the bioavailability of imipramine by decreasing its clearance. The ECG changes appear to result from the increased imipramine levels and the additive effects of both drugs on the atrioventricular conduction time. Diltiazem may similarly affect nortriptyline and trimipramine. 

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