Ramipril Dose-dependently Increases Nitric Oxide Availability in the Radial Artery of Essential Hypertension Patients

Design And Participants: A double-blind, crossover, randomized study was designed to evaluate the effect of 3-month treatment with a lower versus a higher antihypertensive dosage of ramipril (5 or 10 mg/day) on nitric oxide (NO)-dependent vasodilation in 46 untreated patients with essential hypertension. Radial artery flow-mediated dilation (FMD), before and after the intra-arterial infusion of NG-monomethyl-L-arginine (L-NMMA), to block NO synthase, and the response to sublingual glyceril trinitrate (GTN, 25 microg) were measured at baseline and after the two treatment periods as a change in artery diameter (computerized system from ultrasound scans). Plasma angiotensin II and oxidative stress markers were also assessed.

Results: FMD was significantly (P < 0.01) lower in hypertensive patients (4.6 +/- 1.8%) than in normotensive subjects (7.1 +/- 2.6%), whereas the response to GTN was similar. L-NMMA significantly (P < 0.001) inhibited FMD in normotensive but not in hypertensive subjects. Mean 24-h ambulatory blood pressure, plasma angiotensin II and oxidative stress marker levels were similarly reduced at the end of the two treatment periods. Both dosages of ramipril significantly (P < 0.001) increased FMD (5 mg: 5.9 +/- 2.1%; 10 mg: 6.3 +/- 2.4%) without modifying the response to GTN. However, compared with baseline (11 +/- 19%), the inhibiting effect of L-NMMA on FMD (NO-dependent FMD) was significantly (P < 0.01) greater with ramipril 10 mg (49 +/- 12%) than 5 mg per day (38 +/- 15%). The improvement in FMD and NO-dependent FMD was not related to changes in plasma levels of angiotensin II or markers of oxidative stress.

Conclusion: Treatment with ramipril at a higher dosage induced a greater improvement in NO-dependent vasodilation compared with the lower antihypertensive dosage in hypertensive patients.