Conversion from sustained-release to immediate-release calcium entry blockers: outcome in patients with...

We evaluated 110 patients with mild-to-moderate hypertension (diastolic blood pressure 95 to 110 mmHg) whose blood pressure was initially controlled on monotherapy with once-daily sustained-release calcium entry blockers; these patients were then switched to their respective immediate-release formulations TID. The study group consisted of 35 patients on diltiazem controlled delivery (CD) switched to immediate-release diltiazem, 41 patients on nifedipine gastrointestinal therapeutic system (GITS) switched to immediate-release nifedipine, and 34 patients on verapamil sustained-release (SR) switched to immediate-release verapamil. Outcome evaluation included a pair-wise comparison of the following during treatment with both formulations: blood pressure control, need for additional hypertensive agents, side effects, compliance, and cost of therapy. Blood pressure was controlled in 94% of patients switched from diltiazem CD to immediate-release diltiazem; 6% of patients required additional antihypertensive agents. Side effects and compliance were not significantly different between groups. Blood pressure was controlled in 78% of patients switched from nifedipine GITS to immediate-release nifedipine; 22% of patients required additional antihypertensive agents. Side effects, compliance, and cost of therapy were significantly different between groups. Side effects increased from 32% on nifedipine GITS to 58% on immediate-release nifedipine; and compliance decreased from 93% on nifedipine GITS to 76% on immediate-release nifedipine (P < 0.05). Blood pressure was controlled in 91% of patients switched from verapamil SR to verapamil immediate release; 9% of patients required additional antihypertensive agents. Side effects and compliance were not significantly different between groups, but immediate-release verapamil was significantly less expensive than verapamil SR.(ABSTRACT TRUNCATED AT 250 WORDS)