Fundamental Concepts of Azole Compounds and Triazole Antifungals: A Beginner’s Review

Abstract

Azoles are the most widely used drugs in antifungal therapy. They have a wide spectrum of activity against pathogenic fungi that are clinically relevant. However, they have been associated with adverse reactions and toxicity, both of which can be significant in patients. Compared to diazoles, triazoles discriminate better between their intended molecular target, the fungal CYP51 enzyme, and several enzymes of the human CYP450 system. Over the years, this superior discrimination has led to the favoring of triazoles over diazoles in the treatment of systemic mycoses. Nevertheless, despite their being better able to discriminate between the fungal CYP51 and host CYP450 enzymes, they are still capable of inducing significant toxicity and adverse reactions in the host, especially when taken concomitantly with other therapeutic drugs by patients with compromised immune systems. In this writing, we review some of the fundamental concepts regarding the chemistry and mechanisms of action of azole compounds, as well as the spectrum of activity, pharmacokinetics, and adverse effects of triazole antifungals. In addition, we discuss some of the mechanisms that pathogenic fungi have developed to overcome the cytotoxic effects of therapeutic drugs, with an emphasis on triazoles.