2006 Volume 37 Issue 3 Pages 127-133
There are many reports on grapefruit juice (GFJ) increasing the apparent oral bioavailability of several clinically important drugs metabolized by the most abundant isoform of cytochrome P450, i. e. CYP 3A4. Azelnidipine (Calblock ®) is a long-lasting 1, 4-dihydropyridine calcium antagonist currently used in the treatment of hypertension in Japan. In a drug interaction study using human liver microsomes, several CYP3A4 inhibitors and substrates inhibited the oxidative metabolism of azelnidipine to the same extent as nifedipine and felodipine. In order to evaluate the possible interaction of azelnidipine with GFJ in humans, a randomized, two-way crossover study was conducted in eight Japanese healthy volunteers.
A single oral dose of 8mg azelnidipine was administered orally with either 250mL water or GFJ after overnight fasting. Blood samples were drawn periodically up to 24hours after dosing. Plasma concentrations of azelnidipine were measured by liquid chromatography-tandem mass spectrometry (LC/APCI-MS/MS).
Concomitant administration of azelnidipine with GFJ increased the mean Cmax of azelnidipine by 2.5-fold and the AUC by 3.3-fold compared with water; moreover, the time to reach Cmax (tmax) and the mean residence time (MRT) were slightly delayed. No serious adverse events were observed except one subject described mild symptoms of drug-related headache and flushing accompanied with orthostatic hypotension at 4hrs after administration in the GFJ phase.
The results demonstrated the pharmacokinetic interaction between azelnidipine and a single glass of GFJ.
