ABCB1 haplotypes were determined in 534 healthy Finnish volunteers, of whom 24 participated in a pharmacokinetic study on simvastatin and atorvastatin. The frequencies of occurrence of haplotypes c.1236T-c.2677T-c.3435T and c.1236C-c.2677G-c.3435C were 42.7 and 34.4%, respectively. The simvastatin acid AUC(0-12h) was 60% larger, the atorvastatin AUC(0-infinity) 55% larger, and the atorvastatin half-life 24% longer in subjects with the ABCB1 TTT/TTT genotype (n = 12) than in those with the CGC/CGC genotype (n = 12) (P < 0.05), but there were no differences between the two genotypes with respect to the pharmacokinetics of the lactones of these drugs.
This study investigated the effect of terbinafine and voriconazole on the pharmacokinetics of venlafaxine in healthy volunteers. Plasma concentrations of venlafaxine and O-desmethylvenlafaxine (ODV) were measured after ingestion of 75 mg venlafaxine without pretreatment (control), after terbinafine pretreatment, or after voriconazole pretreatment. During the terbinafine phase, the area under the plasma concentration-time curve (AUC(0-infinity)) of venlafaxine was on average 490% (P<0.001) and that of ODV 57% (P<0.001) of the corresponding control value. Terbinafine decreased the AUC(0-infinity) ratio of ODV over venlafaxine by 82% (P<0.001). Voriconazole slightly increased the sum of AUC(0-infinity) of venlafaxine plus AUC(0-infinity) of ODV (active moiety) by 31% (P<0.001). The most likely mechanism for the interaction between terbinafine and venlafaxine is the inhibition of CYP2D6-mediated O-demethylation of venlafaxine, whereas the minor effects of voriconazole are probably due to the inhibition of CYP3A4-, CYP2C9-, or CYP2C19-mediated metabolism of venlafaxine.
This study investigated the effect of voriconazole, an inhibitor of cytochrome P450 2C9 (CYP2C9) and CYP3A4, and itraconazole, an inhibitor of CYP3A4, on the pharmacokinetics and pharmacodynamics of meloxicam. Twelve healthy volunteers in a crossover study ingested 15 mg of meloxicam without pretreatment (control), after voriconazole pretreatment, and after itraconazole pretreatment. The plasma concentrations of meloxicam, voriconazole, itraconazole, and thromboxane B 2 (TxB 2 ) generation were monitored. Compared to the control phase, voriconazole increased the mean area under the plasma concentration-time curve from 0 to 72 h (AUC 0-72 ) of meloxicam by 47% (P < 0.001) and prolonged its mean half-life (t 1/2 ) by 51% (P < 0.01), without affecting its mean peak concentration (C max ). In contrast, itraconazole decreased the mean AUC 0-72 and C max of meloxicam by 37% (P < 0.001) and by 64% (P < 0.001), respectively, and prolonged its t 1/2 and time to C max . The plasma protein unbound fraction of meloxicam was unchanged by voriconazole and itraconazole. Lowered plasma meloxicam concentrations during the itraconazole phase were associated with decreased pharmacodymic effects of meloxicam, as observed by weaker inhibition of TxB 2 synthesis compared to the control and voriconazole phases. Voriconazole increases plasma concentrations of meloxicam, whereas itraconazole, unexpectedly, decreases plasma meloxicam concentrations, possibly by impairing its absorption.Meloxicam is a nonsteroidal anti-inflammatory drug (NSAID) of the oxicam class with selectivity toward cyclo-oxygenase 2 (COX-2) compared to 19). It is widely used in the treatment of osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, and other rheumatological conditions. Meloxicam has an oral bioavailability of 89%, and its maximum plasma concentrations (C max ) are achieved within 4 to 11 h (10, 26). It is extensively bound to plasma proteins (Ͼ99%), mainly to albumin (24). The elimination half-life (t 1/2 ) of meloxicam ranges from 13 to 20 h, and it is suitable for once-daily dosing (24,26). Meloxicam is extensively metabolized in the liver, primarily by polymorphic cytochrome P450 2C9 (CYP2C9) enzyme, and to a minor extent by CYP3A4 enzyme, to four pharmacologically inactive metabolites (6, 24). Only negligible amounts of the parent drug are found in urine and in feces (24). The effect of different genotypes on the pharmacokinetics of meloxicam is not known.Voriconazole is a triazole antifungal agent used both intravenously and orally to treat invasive fungal infections. Voriconazole undergoes extensive oxidative metabolism involving CYP enzymes CYP2C19, CYP2C9, and CYP3A4 (13). Voriconazole is also an inhibitor of CYP2C9, CYP3A4, and CYP2C19 catalyzed reactions both in vitro and in vivo (17,21,23,25). Another triazole antifungal, itraconazole, is a potent inhibitor of CYP3A4 (18, 28), but it is without effect on CYP2C9 in humans (15,27).Because both voriconazole and itraconazole inhibit CYP enzymes involved in the metabolism of meloxicam, ...
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