Diltiazem overdose: pharmacokinetics of diltiazem and its metabolites and effect of multiple dose charcoal therapy. We describe a 38 year-old female who ingested 900 mg of diltiazem. She experienced hypotension, bradycardia and heart block but responded well to supportive care that included normal saline infusion and vasopressors. Calcium administration was not beneficial. Serial plasma concentrations of diltiazem, N-demethyldiltiazem and desacetyldiltiazem were quantified. By comparing the elimination half-life for diltiazem with historical controls, it is concluded that multiple dose charcoal therapy was not beneficial for our patient. 