Treatment Tips
To address any resistant dermatophyte, Elewski recommended getting comfortable with itraconazole. For decades, she said, dermatologists have avoided itraconazole because terbinafine typically costs patients $10 for 3 months. “Itraconazole could be $200 per month,” said Elewski. Because of potential drug-drug interactions and absorption issues — and a boxed warning regarding congestive heart failure — physicians historically reserved itraconazole for severe fungal infections.
Itraconazole labeled dosing for onychomycosis is 200 mg daily for 12 weeks. Elewski favors a two-pronged attack, often combining an -azole antifungal with topical ciclopirox.
Another element that emerging tinea pathogens share is slower response to treatment. For T indotineae, reports appearing in the Journal of the American Academy of Dermatology in 2022 and 2024 suggest duration from 6-8 weeks up to 20 weeks.
To avoid recurrences of resistant T rubrum, Elewski treats for a year. However, she has problems getting itraconazole approved, when often it is the only agent that works. “I’ve written more letters than I like to insurance companies” to document terbinafine failure, she said.
Rarely, said Gold, dermatophyte infections resist both terbinafine and itraconazole. Next-line agents such as voriconazole, which some dermatologists have used for resistant T indotineae, can be much harder to tolerate, with more drug interactions, he said.
And because itraconazole, voriconazole, and posaconazole are all triazoles, added Elewski, the latter two might not work better than the former. But because these drugs might outperform itraconazole in selected cases, she said, “that’s when you want to do fungal susceptibility testing.”
TMVII is so new, said Caplan, that optimal therapy duration remains unclear. “One of the challenges with TMVII is when it gets into the genital skin, it’s a hair-bearing area. And based on various grooming practices, there’s an opportunity for the tinea to get deeper into the hair follicle and dermis. That may also be true of T indotineae.”
Anemic Arsenal
Unfortunately, said Gold, the arsenal of antifungals available in the United States remains limited. “Depending on how you count, there are only three to four classes of antifungal drugs designed to treat severe or invasive infections. So whenever we hear about a new fungal pathogen that’s causing resistant infections, it causes public health concern.”
Promising drugs in development include olorofim (F2G) and fosmanogepix (Basilea), according to Gold. However, he said, the development of these drugs to date has targeted invasive fungal infections such as aspergillosis. In June 2023, the Food and Drug Administration rejected the new drug application for olorofim, requesting additional data and analyses. Regarding fosmanogepix, a double-blinded noninferiority phase 3 trial in invasive yeast infections was recently launched, according to a September 24 press release.
Gold, Caplan, and Elewski reported no relevant financial disclosures. Freeman is a COVID-19 co-author for UpToDate and chair of the AAD Emerging Diseases Task Force.
A version of this article appeared on Medscape.com.