n. an antifungal agent that has been suggested as a treatment for depression resistant to conventional drugs, due to its ability to inhibit the biosynthesis of steroids. No large-scale clinical data support this. Ketoconazole is a potent inhibitor of numerous cytochrome P450 enzymes (particularly CYP3A4) and has significant interactions with psychotropic drugs that utilize this metabolic path. Its numerous interactions and propensity to cause liver damage limit its use. U.S. trade name: Nizoral.