Topical antifungal prescribing could be boosting rise of resistant skin infections

Antifungal cream

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A study led by Centers for Disease Control and Prevention (CDC) researchers suggests the high volume of topical antifungal prescribing could be feeding the emergence and spread of antifungal-resistant infections.

Published yesterday in Morbidity and Mortality Weekly Report, the study found that 6.5 million topical antifungal prescriptions valued at $231 million were filled for Medicare Part D beneficiaries in 2021, nearly half of which were written by high-volume prescribers. And many of these prescriptions could be inappropriate.

"In the setting of emerging antimicrobial resistance, these findings highlight the importance of expanding efforts to understand current prescribing practices while encouraging judicious prescribing by clinicians and providing patient education about proper use," the study authors wrote.

Antifungal-resistant ringworm

The authors, from the CDC and Weill Cornell Medicine, say the findings are a concern because of the emergence and spread of antimicrobial-resistant superficial fungal infections like ringworm.

"This emergence and spread are likely exacerbated by the overuse and misuse of topical antifungals, particularly antifungal-corticosteroid combination creams," they wrote, adding that many prescriptions for these creams are written based on visual diagnosis of superficial fungal infections, with confirmatory diagnostic testing rarely performed.

They note that antifungal-resistant ringworm has been detected in 11 US states to date and has also caused outbreaks of extensive, recalcitrant skin infections in South Asia that don't respond to first-line antifungal treatment.

In an August 25, 2023,clinicians outreach message, the CDC warned that dermatologists in New York City have reported cases of severe ringworm caused by Trichophyton indotineae, a frequently resistant fungus, along with fungal nail infections resistant to terbafine. The message urged clinicians to consider antifungal-resistant ringworm in patients with widespread ringworm lesions that don't improve with first-line topical antifungal agents.

In the setting of emerging antimicrobial resistance, these findings highlight the importance of expanding efforts to understand current prescribing practices while encouraging judicious prescribing by clinicians and providing patient education about proper use.

To understand topical antifungal prescribing patterns and identify those who prescribe a disproportionate volume, the researchers analyzed data from the CMS Medicare Part D Prescribers by Provider and Drug data set, assessing the number of prescriptions of topical antifungals and topical antifungal-corticosteroids and total and average costs. High-volume prescribers were defined as those within the top 10th percentile of prescribers.

Of the 6.5 million topical antifungal prescriptions filled in 2021 (approximately one for every eight Medicare Part D beneficiaries), the most common were for ketoconazole (2.4 million), nystatin (1.9 million), and clotrimazole-betamethasone (0.9 million). The total cost for all antifungal prescriptions was $231 million.

Among more than 1 million unique prescribers, 12.8% prescribed topical antifungals. The highest percentage of prescriptions were written by primary care physicians (40%), followed by nurse practitioners or physician assistants (21.4%), dermatologists (17.6%), and podiatrists (14.1%). High-volume prescribers wrote 44.2% of all topical antifungal prescriptions.

Topical antifungal use likely higher

The authors say the large volume of clotrimazole-betamethasone prescribing is a concern because it's a potential driver of resistant ringworm. They also note that the actual volume of topical antifungal use in the study population is likely higher since most topical antifungal creams can be bought over the counter.

"The large volume of topical antifungals used in the United States warrants increased attention given the infrequent use of confirmatory testing, inaccuracy of diagnosis made by physical examination alone, and the recent emergence of severe and antimicrobial-resistant superficial skin infections," they wrote.

The authors suggest high-volume prescribers should be prioritized for antimicrobial stewardship efforts. In addition, they urge the use of confirmatory diagnostic testing whenever possible by healthcare providers, along with efforts to educate patients on the correct use of topical antifungals, to help promote appropriate prescribing and help control the emergence and spread of antimicrobial-resistant superficial skin infections.

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