CYP3A4 and asthma: Corticosteroids are also a standard therapy for ABPA but there are now numerous reports of toxicity using corticosteroid in combination with itraconazole resulting in adrenal suppression in both asthma and cystic fibrosis (CF) patients with ABPA, owing to itraconazole inhibition of the hepatic cytochrome P450 3A4, which is responsible for metabolic clearance of corticosteroid [28,29].