RESUMO
The effect of rifampin on the in vivo metabolism of the antiretroviral drug efavirenz was evaluated in healthy volunteers. In a cross-over placebo control trial, healthy subjects (n = 20) were administered a single 600 mg oral dose of efavirenz after pretreatment with placebo or rifampin (600 mg/day for 10 days). Plasma and urine concentrations of efavirenz, 8-hydroxyefavirenz and 8,14-dihydroxyefavirenz were measured by LC-MS/MS. Compared to placebo treatment, rifampin increased the oral clearance (by â¼2.5-fold) and decreased maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC0-∞) of efavirenz (by â¼1.6- and â¼2.5-fold respectively) (p < 0.001). Rifampin treatment substantially increased the Cmax and AUC0-12h of 8-hydroxyefavirenz and 8,14-dihydroxyefavirenz, metabolic ratio (AUC0-72h of metabolites to AUC0-72h efavirenz) and the amount of metabolites excreted in urine (Ae0-12hr) (all, p < 0.01). Female subjects had longer elimination half-life (1.6-2.2-fold) and larger weight-adjusted distribution volume (1.6-1.9-fold) of efavirenz than male subjects (p < 0.05) in placebo and rifampin treated groups respectively. In conclusion, rifampin enhances CYP2B6-mediated efavirenz 8-hydroxylation in vivo. The metabolism of a single oral dose of efavirenz may be a suitable in vivo marker of CYP2B6 activity to evaluate induction drug interactions involving this enzyme.
Assuntos
Antirretrovirais/metabolismo , Benzoxazinas/metabolismo , Indutores do Citocromo P-450 CYP2B6/farmacologia , Citocromo P-450 CYP2B6/metabolismo , Rifampina/farmacologia , Adolescente , Adulto , Antirretrovirais/sangue , Antirretrovirais/farmacocinética , Benzoxazinas/sangue , Benzoxazinas/farmacocinética , Estudos Cross-Over , Feminino , Voluntários Saudáveis , Humanos , Hidroxilação/efeitos dos fármacos , Masculino , Pessoa de Meia-Idade , Adulto JovemAssuntos
Adenocarcinoma/tratamento farmacológico , Amenorreia/induzido quimicamente , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Neoplasias da Mama/tratamento farmacológico , Sistema Enzimático do Citocromo P-450/genética , Insuficiência Ovariana Primária/induzido quimicamente , Adolescente , Adulto , Fatores Etários , Amenorreia/genética , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Ciclofosfamida/administração & dosagem , Ciclofosfamida/efeitos adversos , Doxorrubicina/administração & dosagem , Doxorrubicina/efeitos adversos , Feminino , Frequência do Gene , Humanos , Pessoa de Meia-Idade , Projetos Piloto , Polimorfismo de Nucleotídeo Único , Insuficiência Ovariana Primária/genética , Adulto JovemRESUMO
We tested the hypothesis that the stable isotope [(13)C]pantoprazole is O-demethylated by cytochrome P450 CYP2C19 and that the (13)CO(2) produced and exhaled in breath as a result can serve as a safe, rapid, and noninvasive phenotyping marker of CYP2C19 activity in vivo. Healthy volunteers who had been genotyped for the CYP2C19(*)2, CYP2C19(*)3, and CYP2C19(*)17 alleles were administered a single oral dose of [(13)C]pantoprazole sodium-sesquihydrate (100 mg) with 2.1 g of sodium bicarbonate. Exhaled (13)CO(2) and (12)CO(2) were measured by IR spectroscopy before (baseline) and 2.5 to 120 min after dosing. Ratios of (13)CO(2)/(12)CO(2) after [(13)C]pantoprazole relative to (13)CO(2)/(12)CO(2) at baseline were expressed as change over baseline (DOB). Maximal DOB, DOB(15) to DOB(120), and area under the DOB versus time curve (AUC(0-120) and AUC(0-infinity)) were significantly different among three genotype groups (CYP2C19(*)1/(*)1, n = 10; CYP2C19(*)1/(*)2 or CYP2C19(*)1/(*)3, n = 10; and CYP2C19(*)2/(*)2, n = 5) with predicted extensive metabolizers (EMs), intermediate metabolizers (IMs), and poor metabolizers (PMs) of CYP2C19, respectively (Kruskal-Wallis test, p < 0.01); linear regression analysis indicated a gene-dose effect relationship (r(2) ranged between 0.236 and 0.522; all p < 0.05). These breath test indices were significantly lower in PMs than IMs (p < 0.05) or EMs (p < 0.01) of CYP2C19. [(13)C]Pantoprazole plasma exposure showed significant inverse correlation with breath test indices in the respective subjects (Pearson r = -0.74; p = 0.038). These feasibility data suggest that the [(13)C]pantoprazole breath test is a reliable, rapid, and noninvasive probe of CYP2C19 and seems to be a useful tool to optimize drug therapy metabolized by CYP2C19.