Bioavailability and pharmacokinetics of isradipine after oral and intravenous administration: half-life shorter than expected?

Pharmacology & toxicology

PubMedID: 10815751

Christensen HR, Antonsen K, Simonsen K, Lindekaer A, Bonde J, Angelo HR, Kampmann JP. Bioavailability and pharmacokinetics of isradipine after oral and intravenous administration: half-life shorter than expected?. Pharmacol Toxicol. 2000;86(4):178-82.
Isradipine is a calcium channel-blocking agent of the dihydropyridine type, used in the treatment of hypertension. A terminal half-life of 8-9 hr has been reported, in several pharmacokinetic studies after oral administration of isradipine. In a yet unpublished study a much shorter half-life was observed, and the present trial was therefore conducted in order to estimate the half-life after intravenous administration of isradipine. The bioavailability was estimated as well. In a randomised cross-over design ten healthy young volunteers were given either isradipine orally or an intravenous infusion. The two study periods were separated by at least 3 days. Blood samples for measurement of isradipine concentration were collected for 10-12 hr after administration and half-life and bioavailability were estimated. Mean terminal half-life after intravenous administration was calculated to be 2. 8 hr, and the bioavailability to be 0. 28. None of the 10 subjects suffered from side effects. In the present intravenous study the half-life of isradipine seems to be of much shorter than demonstrated in previous oral studies.