Severe, antifungal-resistant dermatomycoses have emerged globally,¹ necessitating increased scrutiny of topical antifungal use and diagnostic testing.² Data are lacking in general outpatient populations on topical antifungal prescribing. We estimated outpatient topical antifungal prescribing rates and evaluated potentially unnecessary prescribing by specialty.

Using Merative MarketScan Commercial and Medicare data, we identified outpatients prescribed topical antifungals during 2023. By specialty seen, we examined patients whose topical antifungal prescription was potentially unnecessary, defined as those who did not have an associated fungal infection diagnostic code and also did not have associated diagnostic testing (Supplementary Material, available via Mendeley at https://data.mendeley.com/datasets/9w9pgcpn4x/1).

Among ~15,700,000 outpatients, 568,715 were prescribed a topical antifungal (rate: 36.2/1000 outpatients) (Table I). Among those, the median age was 47.0 years (interquartile range: 28–61). Most were female (60.8%) and Southern (46.5%) or Midwestern (22.1%) residents. Prescribing rates ( per 1000 outpatients) were highest for patients ≥65 years (73.4), females (40.4), and Northeasterners (45.0). Ketoconazole had the highest prescribing rate (10.2), then clotrimazole-betamethasone (7.3), nystatin (6.4), and nystatin-triamcinolone (2.7). Overall, 16.0% of patients prescribed a topical antifungal received a diagnostic test; this percentage was <25.0% across age groups, sexes, regions, and most topical antifungals.

For over half (51.6%) of patients prescribed a topical antifungal, the prescription was categorized as potentially unnecessary (Table II). This percentage was highest for patients prescribed clotrimazole-betamethasone (73.0%) and nystatin-triamcinolone (60.3%); lowest for those prescribed allylamines (35.6%) and onychomycosis treatments (38.1%); highest for those seen by primary care physicians (49.5%), pediatricians (52.5%), and other or unknown specialty types (73.5%); and lowest for those seen by podiatrists (16.4%) and dermatologists (26.0%). For patients seen by dermatologists, >50% of prescriptions for polyenes, clotrimazole-betamethasone, and nystatin-triamcinolone were potentially unnecessary.

We estimated that topical antifungal prescriptions might have been unnecessary for over half of the >560,000 patients prescribed these medications in 2023. The highest rates of potentially unnecessary prescribing were for antifungal-corticosteroids (clotrimazole-betamethasone and nystatin-triamcinolone), which were among the most frequently prescribed topical antifungals in general, including for dermatologist-associated prescriptions. Antifungal-corticosteroid combination prescribing likely indicates physicians’ attempts to cover both fungal and nonfungal skin rashes when the diagnosis is not confirmed.^3,4 However, clotrimazole-betamethasone and nystatin-triamcinolone can cause systemic side effects and skin damage due to their potent steroid components; further, they may be associated with greater cost and lower cure rates compared with antifungal monotherapy.⁴ Clinicians can consider selecting antifungal monotherapy for fungal infections or dermatology referral in instances of diagnostic uncertainty.³ Diagnostic testing, which can help ensure proper diagnosis and treatment, was infrequent, potentially reflecting barriers to in-office microscopy (eg, lack of time or clinical experience, Clinical Laboratory Improvement Amendments-related restrictions), or low reimbursement.³

Study limitations include lack of information on over-the-counter topical antifungals, patient adherence, treatment outcomes, testing results, and non–commercially-insured populations, as well as potential undercoding and disease misclassification.

Our study found that a substantial proportion of topical antifungal prescriptions were not associated with a fungal diagnosis or diagnostic testing, highlighting potential opportunities to improve clinical practice in an era of emerging antifungal-resistant fungal skin infections.