Comparison of Antihypertensive Effect and Pharmacokinetics of Conventional and Extended Release Felodipine Tablets in Patients with Arterial Hypertension

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Abstract
In 2 separate double-blind, placebo-controlled, crossover studies, the antihypertensive effect and felodipine plasma concentrations were studied after 2 different formulations of felodipine. Both trials studied patients who had previously responded unsatisfactorily to conventional triple therapy (β-adrenergic blocker, diuretic and vasodilator). Felodipine or corresponding placebo was added to the pre-existing β-adrenergic blocker/diuretic combination. Both tablet formulations significantly lowered blood pressure. In patients taking plain felodipine tablets, 10mg bid for 10 days, the blood pressure reduction was evident for 12 hours but not 24 hours after each dose. At steady state, the maximal felodipine plasma concentration was 25.2 ± 1.5 nmol/L and occurred 1.3 ± 0.2 (range 1 to 3) hours after drug intake. When an extended release formulation of felodipine (20mg once every morning) was used, a more even plasma concentration curve was achieved. After 2 weeks’ treatment, the maximal felodipine plasma concentration was 23.3 ± 2.7 nmol/L and was reached 4.4 ± 0.5 (range 3 to 7) hours after each dose. Systolic as well as diastolic blood pressure at steady state were reduced over 24 hours. No disturbing side effects were noted on either felodipine formulation. From these studies we conclude that oral felodipine lowers blood pressure in patients with moderate to severe hypertension when added to a β-adrenergic blocker/diuretic combination. The extended release formulation given in a once-daily long term regimen produced a significant and equally satisfactorily controlled blood pressure reduction over 24 hours compared with the plain tablets but has the advantage of once-daily rather than twice-daily administration.