Gender differences in concentration of itraconazole and hydroxyitraconazole

Abstract

Introduction: Itraconazole is an antifungal drug belonging to the triazole group. After oral application, it is rapidly absorbed, but its bioavailability is reduced due to an intensive first-pass through the liver metabolism effect. A large number of metabolites (the most important of which is hydroxyitraconazole) are produced by isoform CYP3A4 of cytochrome P450. The variability of itraconazole pharmacokinetics is the result of numerous factors that have not yet been fully clarified. Our study aimed to investigate the influence of gender on itraconazole and hydroxyitraconazole plasma concentrations in healthy adults after an oral application of a single dose of itraconazole. Methods: Pharmacokinetic analysis was performed after oral administration of itraconazole in a single dose of 100 mg to 22 male and 16 female healthy volunteers. Blood samples were collected before taking the drug and at appropriate time intervals up to 72 hours later. Itraconazole and hydroxyitraconazole concentrations were determined using a validated liquid chromatography method with mass spectrometric detection (LC-MS/MS) and their pharmacokinetic parameters were calculated by using the Kinetica programme, version 5.0: Cmax, Tmax, PIK (0-72), PIK (0-∞), T1/2, and Ke. Results: The median values of both itraconazole and hydroxyitraconazole were lower in women in comparison to men during the whole period of observation. Moreover, median values of Cmax, PIK(0-72) and PIK(0-∞) parameters were also significantly lower in women, concerning both itraconazole (p=0.005, 0.036 and 0.036, respectively) and its metabolite (p=0.004, 0.010 and 0.044, respectively). Elimination parameters - T1/2 and Ke did not differ between genders. Conclusion: Women were less exposed to itraconazole and its active metabolite than men following an oral application of the drug, possibly as a result of lower bioavailability due to a more intense pre-systemic metabolism, as a result of a higher expression and/or activity of the isoform enzyme, which metabolises itraconazole, and which would need to be confirmed by pharmacogenomic analysis.