Comparative Efficacy, Safety, and Kinetics of Immediate-and Slow-Release Verapamil in Hispanic Patients with Essential Hypertension

We assessed the pharmacokinetics and pharmacodynamics of immediate-release (IR) and slow-release (SR) verapamil in Hispanic patients with mild to moderate essential hypertension. Area under the curve and Cmax increased linearly with the dose of IR and SR. Plasma levels showed a more gradual increase and were maintained elevated for longer periods with SR. Both IR and SR reduced blood pressure (BP) significantly. Peak BP reduction with 240 mg q.i.d. SR (6 h postdose) or 80 mg t.i.d. IR (4 h postdose) averaged 28/18 and 23/20 mm Hg, respectively. Morning predose BP levels were reduced 16/5 mm Hg by SR and 5/6 mm Hg by IR. Peak PR prolongation averaged 43 ms for SR and 56 ms with IR. Heart rate was not modified. With 480 mg/day there was a greater BP reduction with no relevant changes in HR and no further increases in PR intervals. However, incidence of side effects (headaches, dizziness) was enhanced with 480 mg/day IR but not with SR. These results suggest that Hispanic patients have a good response to verapamil. The pharmacokinetic characteristics of SR verapamil account for its more favorable side-effect profile observed with this formulation. SR is considered advantageous to IR for the chronic treatment of hypertensive patients.