A comparison of the acute hypotensive effects of two different doses of nifedipine

Abstract

To determine whether a dose of 5 mg of nifedipine would be useful in the treatment of hypertensive emergencies, we compared the acute hypotensive effects of two different doses of nifedipine, 5 mg and 10 mg, in patients with severe hypertension. In this prospective, randomized, double-blind study, 30 consecutive black patients with diastolic blood pressure that was equal to or greater than 115 mm Hg received either a 5 mg or 10 mg nifedipine capsule and a placebo capsule, which matched that of the alternative strength. Patients were asked to bite the capsules and swallow the contents. Blood pressure response over 4 hours and adverse effects were monitored. Mean systolic blood pressure was reduced from 191.7 mm Hg (95% confidence interval 170.8 to 212.7 mm Hg) to 157.9 mm Hg (137.0 to 178.9 mm Hg) and 206.1 mm Hg (185.1 to 227.0 mm Hg) to 153.7 mm Hg (132.8 to 174.7 mm Hg) in patients who were given 5 mg and 10 mg doses of nifedipine, respectively. Mean diastolic blood pressure in the group of patients that reveived 5 mg doses of nifedipine decreased from 128.2 mm Hg (115.6 to 140.7 mm Hg) to 105.2 mm Hg (92.7 to 117.7 mm Hg); the corresponding values in the group that received 10 mg doses of nifedipine were 129.9 mm Hg (117.4 to 142.5 mm Hg) and 97.5 mm Hg (85.0 to 110.1 mm Hg), respectively. The minimum mean systolic blood pressures occurred 20 and 25 minutes after administration of the 5 mg and 10 mg capsules, respectively; the minimum diastolic blood pressures were reached after 20 and 30 minutes, respectively. The mean basal and maximal post-treatment heart rates in patients who were given the 5 mg and 10 mg capsules were 65.5 beats/min (95% confidence intervals; 56.6 to 74.3 beats/min) and 71.6 beats/min (62.7 to 80.5 beats/min), and 66.5 beats/min (57.7 to 75.4 beats/min) and 72 beats/min (63 to 80 beats/min), respectively. One patient who had fallen asleep between blood pressure measurements woke up restless and mildly agitated 25 minutes after he had been given 10 mg of nifedipine; he settled down after reassurance was provided. There were no other adverse effects. These data indicate that both the 5 mg and the 10 mg doses of nifedipine, which were given in capsule form by the bite and swallow method, would be useful in the treatment of hypertensive emergencies. To avoid profound hypotension, it is advisable to use the lower dose (i.e., 5 mg of nifedipine). If a satisfactory response is not obtained, the dose may be repeated when the blood pressure has reached its nadir (usually within an hour). Thereafter, maintenance antihypertensive therapy will be needed and should be started 2 hours after patients have received 5 mg of nifedipine and 4 hours after they have received 10 mg of nifedipine.