Arterial vasodilator and antihypertensive effects of diltiazem

The arterial vasodilator properties of the calcium antagonist diltiazem were investigated by measurement of changes of forearm blood flow during brachial artery infusions of eight dosages of diltiazem in eight hypertensive patients. Forearm blood flow increased and calculated forearm vascular resistance decreased dose-dependently (maximum decrease of 83.5 +/- 8.6%). When comparing the effects of calcium influx inhibition by diltiazem with stimulation of the vascular cyclic guanosine monophosphate (GMP) system by sodium nitroprusside, the vasodilation by diltiazem was approximately 1.6 times greater, attesting to its potent arterial vasodilator activity. The clinical efficacy and feasibility of diltiazem monotherapy was evaluated in 40 patients with mild to moderate essential hypertension treated with a slow-release formulation of diltiazem, 90 mg twice daily over 8 weeks, and in a subgroup of 21 patients with two tablets of 90 mg once daily in the morning over a period of 2 weeks. Blood pressure was lowered significantly and to a similar extent by either twice- or once-daily administration of diltiazem. This effect was maintained during open long-term therapy over a mean of 11 months. Heart rate and body weight did not change. Thus, the vasodilator properties of diltiazem can be utilized for effective long-term treatment of hypertension. The possibility of once-daily dosing may prove useful with respect to drug compliance in the long-term treatment of a generally asymptomatic disease such as hypertension.