Therapeutic drug monitoring in dermatophytosis: Time to reconsider itraconazole and terbinafine exposure targets

Superficial fungal infections affect nearly one-quarter of the global population and are now a major clinical and public health challenge in South Asia. Dermatophytosis, once a nuisance infection, has become chronic, widespread, and increasingly resistant to therapy. The rise of Trichophyton indotineae and terbinafine (TBF) resistance exceeding 70% in some centers has left dermatologists struggling with high relapse rates and limited effective options. Much of this crisis reflects the gap between prescribed dose and achieved drug exposure. Itraconazole (ITZ) absorption is highly variable, influenced by gastric acidity, diet, and formulation quality, while TBF’s reliability is undermined by genetic resistance. These pharmacological realities explain why standard regimens often fail in practice. Therapeutic drug monitoring (TDM), already standard for triazoles in invasive fungal disease, has untapped value in dermatology. Measuring early ITZ levels can identify underexposed patients, guide use of newer super-bioavailable formulations, and avoid unnecessary treatment failure. TBF monitoring is less often required but can help distinguish poor absorption from true resistance. Newer tools, such as finger-prick microsampling, may make drug level testing practical even in routine dermatology clinics. Reframing dermatophytosis as a disorder of drug exposure as well as resistance highlights the need for precision therapy. Incorporating TDM into dermatology practice could improve cure rates, reduce relapse, and restore confidence in systemic antifungal therapy in the face of rising resistance.