Comparison of bioavailability and pharmacodynamics of diltiazem from two pharmaceutical preparations

Diltiazem, a calcium channel blocker, is used in multiple divided doses daily, due to its short elimination half-life. Hence, administration as a modified release (MR) formulation is suggested. In this double blind cross-over trial, the pharmacokinetics and pharmacodynamics of diltiazem was studied in eight healthy Indian adults. Diltiazem was administered as single dose (60 mg) of the two formulations viz immediate release (IR) and MR. Venous blood samples, for estimation of diltiazem by HPLC, were collected at frequent intervals and BP, HR and ECG were monitored during the 12h study period. With MR formulation, plasma half-life was significantly (P < 0.05) prolonged (6.25 +/- 1.2 h vs. 2.69 +/- 0.2 h), the extent of alterations in BP, HR and PR interval was significantly less, while the duration of prolongation of PR interval was significantly more as compared to IR formulation. Therefore, MR formulation of diltiazem has better pharmacokinetic and pharmacodynamic profile as compared to IR formulation.