Comparison of felodipine extended release and conventional tablets in essential hypertension using ambulatory blood pressure monitoring

Two formulations of felodipine, conventional and extended release (ER) tablets, were compared in a double-blind, crossover study of patients whose blood pressure was not being controlled using metoprolol 100mg once daily. Nineteen patients with a supine diastolic blood pressure ⩾95 mmHg after 4 weeks of taking metoprolol and placebo were randomly assigned to felodipine conventional (5 mg twice a day) or ER (10 mg once daily) for 4 weeks. A 2-week washout period was then followed by 4 weeks of treatment with the alternative formulation. Metoprolol once daily was taken concomitantly throughout the study. Clinic blood pressure was measured at Oh (i.e.t2h after the last dose of conventional, and 24h after the last ER felodipine dose), and then 2 and 5h after the following dose had been taken. Ambulatory blood pressure and the heart rate were monitored over 24h using an Accutracker (Suntech Medical Instruments, Raleigh, North Carolina, USA). During the final treatment, both felodipine formulations caused similar substantial falls in supine blood pressure compared with pressures prior to randomized treatment. The falls in clinic blood pressures (systolic/diastolic) were similar with the conventional and ER formulations at all time points, i.e. Oh (21/13; 19/11 mmHg), 2h (39/18; 36/18mmHg) and 5h (30/12; 35/11 mmHg) after the morning dose was taken. Both formulations also produced similar falls in blood pressures over 24h and during the daytime (21/12; 20/12mmHg). The mean overnight (2300-0800h) blood pressures were slightly but significantly lower (P < 0.05) during treatment with conventional (134 ± 20/78 ± 16 mmHg, mean ± s.d.) than with ER tablets (139 ± 20/81 ± 14 mmHg). However, it is unlikely that this difference is of clinical significance. We conclude that felodipine ER is an effective antihypertensive drug which can be administered on a once-daily basis.