Effect of grapefruit juice on pharmacokinetics of microemulsion cyclosporine in African American subjects compared with Caucasian subjects: Does ethnic difference matter?

This study aims to determine the effect of grapefruit juice (GJ) on microem ulsion cyclosporine (CsA) in 11 African American subjects, and it was compa red to those in Il Caucasian subjects. Each subject received two oral doses of CsA with water(W) or GJ as well as IV CsA. Regardless of race, GJ signi ficantly increased the peak concentration (C-max) and area under the time-c urve (AUC) of CsA; however, the magnitude of GJ effects was different betwe en African American subjects and Caucasian subjects (p = 0.0003). GJ increa sed peak concentration of CsA by 39% in African American subjects, while th e difference in Caucasian subjects was only 8 % (p > 0.05). GJ also increas ed AUC of CsA in African American subjects by 60%, while GJ increased that in Caucasian subjects by 44% (p = 0.0001). The absolute bioavailability of CsA was 21% lower in African American subjects compared with Caucasian subj ects when it was given with water(p = 0.048), but these differences disappe ared when it was given with GJ (p = 0.6). These findings suggest that concu rrent administration of GJ increases the bioavailability of CsA in African American subjects in greater magnitude compared with Caucasian subjects. Jo urnal of Clinical Pharmacology, 2001;41:317-323 (C) 2001 the American Colle ge of Clinical Pharmacology.