Drug interactions of itraconazole in patients under treatment for different mycoses

Abstract

Some studies have reported an increasing number of clinically significant interactions of itraconazole in patients receiving drugs known to have profound effects on the cytochrome P-450 enzyme system. With the purpose of determining the epidemiological, pharmacological and clinical characteristics of drug interactions in patients under therapy with itraconazole, twenty-one patients with clinical and laboratory information suspicious of interaction were included in this transversal retrospective study undertaken during the period of 199441997, Six patients presented paracoccidioidomycosis, five chromoblastomycosis, four histoplasmosis, four cryptococcosis and two aspergillosis. Most of patients had either an underlying or concurrent illness like AlDS or tuberculosis. The average dose of itraconazole was 223.8 mglday, the mean duration of therapy was 23.1 weeks and each patients received around 2.6 drugs simultaneously administered with itraconazole. Drug interaction (undetectable or non-therapeutic serum concentrations of itraconazole) was found in 18 patients and rifampin, H, blockers, antiacids and phenytoin were the most common drugs implicated. According to some published articles, the concurrent administration of these drugs and itraconazole disturbed the absorption and metabolism of this antifungal, subsequently decreased its serum concentration and provoked therapeutic failure. This study is an initial approach that will allow to establish clues for the management of patient under therapy with itraconazole and other therapies and at risk of developing drug interactions.