Bioequivalence of a slow-release and a non-retard formulation of isradipine.

Pharmacokinetic studies were carried out in 48 healthy male volunteers to determine the pharmacokinetic properties of a new modified-release formulation of isradipine (SRO) and to compare these with the pharmacokinetic properties of the nonretard form of isradipine (NR). Studies were carried out in the fasting state and also following a light meal. The time required to reach maximum plasma concentration (tmax) was extended from approximately 1.5 h with NR to 5 to 7 h with SRO, and the maximum plasma concentration [Cp(tmax)] was reduced by around 50%. The bioavailability of SRO was increased by less than 20% compared with the same daily dose given as NR, indicating that the two forms are bioequivalent and that no adjustment in the total daily dose of isradipine is necessary when switching from one form to the other. Administration with a light meal altered the pharmacokinetic parameters by less than 20% compared with administration without food.