Objective: To investigate the possibility and utility of metformin alone or in combination with fosinopril to reduce blood pressure in patients with essential hypertension.
Methods: A total of 140 cases of non-diabetic essential hypertension with hyperinsulinemia were recruited and randomly assigned to two groups: a group of 68 treated with metformin 500 mg tid and a group of 72 treated with fosinopril 10 mg qd. The duration of the treatment was 8 weeks. Combination therapy with the two drugs was used after 4 weeks of treatment if needed. If the target goals of systolic blood pressure (SBP) < 140 mm Hg (1 mm Hg = 0.133 kPa) and/or diastolic blood pressure (DBP) < 90 mm Hg were not attained 4 weeks, combination therapy with two drugs was used in either group in the next 4 weeks. The changes of blood pressure and insulin sensitivity of the two groups were observed before and after treatment.
Results: (1) After 4 weeks of treatment, SBP in metformin group and fosinopril group decreased by (13.0 +/- 1.2) mm Hg and (15.4 +/- 1.4) mm Hg, and DBP decreased by (9.0 +/- 1.0) mm Hg and (10.4 +/- 1.1) mm Hg respectively. After 8 weeks of treatment, SBP in metformin group and fosinopril group decreased by (17.8 +/- 1.5) mm Hg and (20.9 +/- 1.5) mm Hg, and DBP decreased by (13.2 +/- 0.9) mm Hg and (15.3 +/- 1.1) mm Hg respectively. There was no significant difference in the decline of blood pressure between the two groups (P > 0.05). The rates of combination therapy were both 54% in the two groups. (2) Fasting insulin as well as 30 min and 120 min insulin levels after oral glucose tolerance test and insulin area under the curve in the metformin group were significantly reduced after 4 and 8 weeks of treatment as compared with those of baseline (P < 0.05 and P < 0.01). In the fosinopril group, however, they decreased only after 8 weeks treatment (P < 0.05). The insulin action index in the metformin group was higher than that in the fosinopril group after 4 weeks of treatment (P < 0.05), but there was no significant difference between the two groups after 8 weeks of treatment (P > 0.05).
Conclusion: Metformin and fosinopril have similar antihypertensive effect and a good synergy in essential hypertension with hyperinsulinemia.