Hypotensive effects of diltiazem to normals and essential hypertensives

The hypotensive effect of acute and long-term, intravenous and oral administration of the calcium antagonist, diltiazem, was investigated in 8 normotensive volunteers and 55 patients with essential hypertension. Diltiazem i.v. infusion of 45 mg/h (0.5 mg/min, then 1.0 mg/min, each for 30 min rapidly decreased both blood pressure (BP) from 164±22/98±8 to 144±15/86±9 mmHg (mean±SD) and total peripheral resistance from 32.6±8.4 to 25.3±5.4 mmHg/l/min (p<0.001), and increased stroke volume from 58.2±9.5 to 64.2±8.6 ml/beat (p<0.05). It altered neither heart rate nor cardiac output in the hypertensives (n=10). Oral diltiazem 60 mg rapidly decreased BP from 155±10/103±6 to 142±12/90±8 mmHg after 3 hours (p<0.01/p<0.001) in hypertensives (n=8), but not in normotensives (n=8). Diltiazem 90 mg p.o. decreased BP from 157±15/102±9 to 129±13/83±8 mmHg (p<0.01) in hypertensives (n=15), and reduced the heart rate from 71±8 to 65±8 beats/min (p<0.01). The drug did not change plasma renin activity either in normotensives or hypertensives. The fall in diastolic BP was correlated with the plasma diltiazem concentration (r=0.910, n=6, p<0.05). Long-term treatment with diltiazem 30mg t.d.s. decreased BP from 163±12/104±8 to 145±9/88±9 mmHg (p<0.001, n=13), and 60mg t.d.s. decreased BP from 169±15/102±6 to 148±13/87±8 mmHg (p<0.001, n=8), and significantly reduced the heart rate (p<0.01) in hypertensives. Thus, the hypotensive action of diltiazem, which is due to arterial dilatation, is effective, either on intravenous or oral administration, during acute and long-term treatment of essential hypertension.