A total of 152 patients with essential hypertension (World Health Organization 
classification I/II) entered a multicenter randomized study to assess the safety 
and efficacy of isradipine compared with, and in combination with, the 
beta-blocker atenolol. After a three-week placebo treatment period, patients 
received either isradipine (2.5, 5, 7.5, or 10 mg twice daily) or atenolol (50 
or 100 mg once daily) for seven weeks. Patients who did not have an adequate 
response (diastolic blood pressure less than 90 mm Hg) with the maximal doses of 
single-drug therapy were given a combination of both drugs for a further seven 
weeks. Both drugs resulted in significant and clinically relevant reductions in 
blood pressures. Although the reduction in diastolic blood pressure was the same 
for patients receiving the two drugs, there was a statistically significant 
greater reduction in systolic blood pressure in the isradipine group, suggesting 
that this drug has a more favorable effect on vascular impedance. Of the 14 
patients who did not attain normal blood pressure levels (sitting diastolic 
blood pressure less than 90 mm Hg) receiving monotherapy, 12 patients reached 
this goal with a combination of the two drugs.