In fact, these drugs are primarily metabolized in the liver through cytochrome P450 (CYP450) enzymes, mainly CYP3A4 and CYP3A5, which are inhibited by several drugs concomitantly administered to CF patients such as triazole antifungal agents, antivirals and macrolide antibiotics (i.e., clarithromycin and erythromycin) [12,22]. The gene discussed is CYP3A5; the disease is cystic fibrosis.