The authors report the case of a serious cardiovascular complication due to naftidrofuryl overdosage following its intravenous administration. Other similar complications have already been reported in the literature and in experimental animal studies (particularly involving the conduction system of the heart). Since naftidrofuryl belongs to the class of local anesthetics and is pharmacologically related to procainamide, certain precautions must be closely followed if it is administered intravenously: avoidance of rapid injection directly into the vein, limiting the infusion to 200 to 400 mg given over a 3 hour period using preferably a constant infusion syringe pump or an infusion pump, and using caution when associated with other medications, particularly antiarrhythmic agents which could affect atrioventricular or intraventricular conduction.