PHARMACOKINETICS AND PHARMACODYNAMICS OF A SLOW-RELEASE FORMULATION OF DILTIAZEM AFTER THE ADMINISTRATION OF A SINGLE AND REPEATED DOSES TOHEALTHY-VOLUNTEERS

Diltiazem is a calcium antagonist used in angina pectoris and hyperten sion. There is little information concerning the slow-release (SR) for mulation in the literature. The pharmacokinetics of diltiazem SR (120 mg) have been assessed over a 36 h period in healthy volunteers after single- (SD) and multiple-dose (MD) administrations. C-max, AUC(0-36), and AUC(0-infinity) were significantly increased at steady state comp ared to the extrapolated SD values, suggesting accumulation of the dru g. Renal and cardiovascular parameters have also been assessed at inte rvals of 3-6 h during baseline (B) and following single and multiple d oses of diltiazem SR. Diuresis over a 24 h period was increased, but n ot significantly, by the administration of diltiazem SR i.e. 1782 ml ( MD) and 1915 ml (SD), versus 1626 ml (B). Natriuresis and creatinine c learance were slightly decreased by diltiazem SR, compared to B values ; this might be due to the relatively short period over which steady s tate was maintained (five days) and the effects of norepinephrine and angiotensine II on renal vasculature and the pharmacokinetics of dilti azem SR. No increase in the systolic blood pressure occurred after the administration of diltiazem SR; diastolic blood pressure and PR inter val were decreased and increased respectively by diltiazem SR. These r esults do not appear to be clinically significant. Finally, no relatio n was found between the pharmacokinetics and pharmacodynamics of dilti azem. This may be attributed to the absence of clinically significant effects in healthy volunteers, the presence of active metabolites, the pharmacokinetics of the SR formulation and/or the accumulation of the drug at steady state.