Comparison of effects of enalapril and captopril on serum potassium concentration in the treatment of malignant hypertension.

To compare the effects of enalapril and captopril on blood pressure, serum creatinine (S-Cr), and potassium (S-K) levels, patients with malignant hypertension treated with either 5-10 mg of enalapril (eight cases) or 75-400 mg of captopril (eight cases) were investigated retrospectively. After 2 weeks of treatment, the average blood pressure fell from 214/138 to 132/89 mmHg on enalapril and from 240/145 to 147/95 mmHg on captopril. The percent change in mean blood pressure during the 2 weeks of treatment with enalapril (-35.6 +/- 4.0 SE%) was similar to that with captopril (-35.8 +/- 2.8%). S-Cr did not change in both groups, while S-K increased significantly from 3.9 +/- 0.2 to 5.2 +/- 0.2 mEq/l on enalapril and from 3.6 +/- 0.2 to 4.2 +/- 0.1 mEq/l on captopril. S-K at the second week was significantly higher in the enalapril than in the captopril group. The maximum S-Cr concentration during the treatment was correlated with the corresponding S-K concentration similarly in both groups. These results indicate that both enalapril and captopril increase S-K without deterioration of renal function in patients with malignant hypertension and that the way these drugs are used in clinical practice may be more likely to result in elevated S-K with enalapril.