Prescribing and costs of topical antifungals for onychomycosis by podiatrists in Medicare Part D

INTRODUCTION

Onychomycosis is a chronic fungal infection of the nail plate and nail bed caused mainly by dermatophytes, with yeasts and non-dermatophyte molds contributing in specific populations.(1) It affects roughly one in ten adults in community-based estimates, and its prevalence rises with age, diabetes, immunosuppression and peripheral vascular disease. Tinea pedis frequently coexists with and precedes nail involvement, so the two conditions are often managed together.(2) The infection is more than a cosmetic problem: it causes nail discoloration and thickening, can produce pain on ambulation, and, in people with diabetes, predisposes to secondary bacterial infection, ulceration and potentially serious limb complications.(3) The burden also extends to children and adolescents, in whom dermatophyte onychomycosis is increasingly recognized.(4) Because the condition is common, chronic and recurrent, and because many patients remain untreated or receive repeated courses of therapy, the volume and cost of its pharmacological treatment are relevant to payers and to the clinicians who manage the nail on a routine basis.

Topical antifungals occupy a defined place in that treatment armamentarium. They avoid the systemic drug interactions and hepatic monitoring associated with oral terbinafine and the azoles, which is particularly valuable in older adults and in patients with diabetes who receive multiple medications.(5) Ciclopirox 8% nail lacquer was for years the only widely available topical option, although its mycological cure rates are modest and its effectiveness depends on regular debridement.(6) The approval of efinaconazole 10% solution and tavaborole 5% solution in 2014 expanded the topical armamentarium. Efinaconazole in particular penetrates the nail plate more effectively than ciclopirox and achieves higher mycological cure rates.(7,8) Post hoc analyses of the phase 3 trials and a pooled analysis in white, Black and Asian participants have confirmed the efficacy and safety of efinaconazole in older adults and across racial groups.(9,10) In vitro and ex vivo studies likewise document antifungal activity and nail penetration for the topical agents used in clinical practice.(11)

Despite this evidence, topical antifungal prescribing in the United States has been described as simultaneously insufficient and excessive, depending on the measure examined. An analysis of the National Ambulatory Medical Care Survey found that treatment was prescribed at only about one fifth of onychomycosis visits.(12) In contrast, studies of commercial insurance claims reported opportunities to improve guideline adherence in diagnosis and treatment and identified high rates of potentially unnecessary topical antifungal prescriptions.(13,14) A registry-based cohort described patient characteristics, diagnostic testing utilization and antifungal prescribing patterns for onychomycosis in the United States between 2016 and 2022, and found that diagnostic confirmation is obtained in only a minority of treated patients.(15) In Medicare Part D, specialty medications account for a large and rising share of dermatologic drug spending, but the specific contribution of podiatrist prescribing of topical antifungals has not been quantified.(16) The public release of prescriber-level Part D records makes such quantification feasible, because the files combine prescriber specialty, drug identity, annual volume and cost in a single national source that is updated each year.

Podiatrists are frequent first-contact providers for nail disorders and are therefore central to how topical antifungals are actually used in everyday practice. They perform nail debridement, obtain mycological samples and initiate or renew topical prescriptions, yet national data describing their prescribing behavior are scarce. It is not known how the adoption of efinaconazole and tavaborole has progressed among podiatrists since 2014, whether the older generic ciclopirox has been displaced, or how drug costs for these three products vary across states. Answering these questions requires a data source that identifies the specialty of the prescriber together with the specific drug, which is precisely the structure of the Medicare Part D Prescribers by Provider and Drug files. Such information is directly relevant to prescribing stewardship, to formulary decisions and to the training and continuing professional education of podiatric clinicians who treat nail disease in ambulatory practice.

This study aimed to describe the evolution of topical antifungal prescribing by podiatrists in Medicare Part D between 2014 and 2024 and to quantify between-state variation in drug costs. We tested three hypotheses. H1: the annual volume of topical antifungal prescribing by podiatrists increased over the study period. H2: the combined share of claims for efinaconazole and tavaborole rose over the period, although ciclopirox remained the most prescribed agent. H3: per-beneficiary drug costs varied substantially across states and were positively associated with the state-level share of branded agents.

METHODS

RESULTS

Between 2014 and 2024 the analysis included 46,239 prescriber-drug records contributed by 9,834 distinct podiatrists across the fifty states, the District of Columbia and United States territories. Cumulatively the records represented 2,294,272 claims, 2,467,254 30-day fills and 265.2 million United States dollars in drug costs. The annual number of contributing prescribers grew in every year of the series.

H2. Prescribing shifted toward branded agents while ciclopirox remained dominant

Efinaconazole and tavaborole entered the market in 2014, and their combined share of claims rose from 0.1% that year to 14.3% in 2024 (Table 2; Figure 1). In 2024 efinaconazole accounted for 35,417 claims and 41,573,180 United States dollars in drug costs, tavaborole for 14,261 claims and 7,510,001 United States dollars, and ciclopirox for 298,365 claims and 9,010,878 United States dollars. The branded share of claims was 14.3%, composed of 10.2% for efinaconazole and 4.1% for tavaborole, whereas ciclopirox retained 85.7% of claims. The distribution of spending differed from the distribution of claims: efinaconazole represented 10.2% of claims and 71.6% of drug costs, whereas ciclopirox represented 85.7% of claims and 15.5% of costs. In terms of 30-day fills, the corresponding volumes were 38,748 for efinaconazole, 17,225 for tavaborole and 322,937 for ciclopirox. The Cochran-Armitage test confirmed a monotonic increase in the branded share over the period (z = 237.2; p <0.001), and the exact binomial confidence interval for the 2024 share was 14.2-14.4%. Ciclopirox nevertheless remained the dominant agent in every year of the period. H2 was confirmed.

Year	Efinaconazole (claims)	Tavaborole (claims)	Ciclopirox (claims)	Branded share (%)
2014	134	0	133983	0.1
2015	4849	1343	148565	4.0
2016	4767	2362	154817	4.4
2017	4639	1927	158954	4.0
2018	6592	1027	177057	4.1
2019	8796	1234	196670	4.9
2020	8230	1188	168543	5.3
2021	10783	5491	194676	7.7
2022	15170	12516	224961	11.0
2023	23881	15574	257500	13.3
2024	35417	14261	298365	14.3

Note: Branded agents comprise efinaconazole and tavaborole; ciclopirox is the generic comparator. Source: Elaborated from the CMS Medicare Part D Prescribers - by Provider and Drug public use files (data.cms.gov).

H3. Per-beneficiary costs varied widely across states

In 2024 the cross-state analysis included 50 jurisdictions after the exclusion of South Dakota, which reported no beneficiary counts (Table 3; Figure 2). Per-beneficiary drug cost ranged from 42.1 United States dollars in ID to 1,307.0 in NY, with a median of 164.8. The coefficient of variation was 103.8%, the interquartile range 225.4 United States dollars and the ratio between the 90th and 10th percentiles 9.7. The branded share of claims also varied across jurisdictions, from 0.0% to a maximum of 55.8% in OR. Per-beneficiary cost was strongly associated with the state branded share of claims (Pearson r = 0.94; p <0.001), and the Spearman correlation was similar (rho = 0.95; p <0.001). H3 was confirmed.

State	Claims (n)	Beneficiaries (n)	Cost per beneficiary (USD)	Branded share (%)
NY	62399	21636	1307.0	40.9
DC	854	326	1076.0	33.1
OR	3025	1372	1045.4	55.8
MA	4768	1858	675.6	24.1
CT	4915	1989	597.2	20.1
NJ	22726	8119	596.1	16.2
CO	1448	540	490.1	14.6
NE	156	37	466.9	7.1
MD	5086	2243	463.9	19.0
AK	148	54	442.2	10.1
RI	811	301	423.9	17.1
KS	511	198	362.6	12.1
VT	186	79	321.9	8.1
CA	45628	19822	315.1	14.9
UT	616	292	252.0	11.4
HI	316	143	243.1	8.2
VA	6028	2813	242.3	10.6
AL	2993	1481	219.4	8.5
WI	3563	1644	207.4	5.9
MO	3381	1508	200.1	9.1
TX	27234	13343	192.9	7.3
AZ	5041	2390	191.6	6.6
OK	1550	742	186.0	5.5
DE	1348	583	177.7	5.6
IN	2719	1291	170.3	6.1
TN	3018	1535	159.2	5.3
ME	153	26	154.2	0.0
SC	4365	2203	153.7	4.9
PA	13540	5504	151.1	4.4
NC	7946	3860	141.0	3.9
FL	47640	22115	132.8	3.3
MS	1818	884	127.8	5.2
IL	8414	4037	116.5	3.2
NV	1821	872	109.5	2.8
LA	5479	2747	107.6	2.6
OH	10180	4764	105.1	2.2
WA	2057	825	103.7	2.2
IA	756	269	91.8	0.0
NH	322	129	81.8	0.0
GA	9618	4881	78.5	1.4
WY	61	22	78.2	0.0
MI	5866	2847	73.9	1.9
AR	818	439	63.8	0.0
NM	1282	589	62.5	0.0
KY	2042	1014	61.8	1.2
MT	246	93	60.3	0.0
WV	964	457	56.4	0.0
MN	1825	908	55.8	0.7
ND	38	19	52.6	0.0
ID	227	130	42.1	0.0

Note: States ordered by cost per beneficiary; South Dakota was excluded because no beneficiary counts were reported. USD = United States dollars. Source: Elaborated from the CMS Medicare Part D Prescribers - by Provider and Drug public use files (data.cms.gov).

DISCUSSION

The principal finding of this study is that podiatrist prescribing of topical antifungals for onychomycosis in Medicare Part D expanded steadily over eleven years, that spending grew faster than prescribing volume because of a modest shift toward branded agents, and that per-beneficiary costs differed more than ninefold across states in line with the local share of those branded agents.

These estimates describe a Medicare population that is older, more heavily treated and more comorbid than the commercially insured population examined in most prior studies of onychomycosis prescribing.(3,5) The findings are therefore best interpreted as the behavior of clinicians who manage the disease in exactly the group in which topical therapy is most attractive, namely older adults with polypharmacy and, frequently, diabetes. Generalization to younger, commercially insured patients should be made with caution, although the underlying drivers of prescribing, such as price, familiarity and efficacy expectations, are unlikely to be unique to Medicare. The analysis also captures prescriptions only for beneficiaries enrolled in Part D, so uninsured patients and those covered by other plans are not represented, and the state-level differences cannot be attributed to any single formulary or benefit design.

The growth in prescribing volume is consistent with the broader expansion of prescription drug spending in fee-for-service Medicare and with the rising concentration of that spending in specialty products.(22,23) Within dermatology, specialty medications now account for a substantial and increasing share of Medicare Part D expenditures, which places a drug class such as the topical onychomycosis agents within a larger spending trend.(16) The interruption observed in 2020 coincides with the sharp reduction in ambulatory care during the COVID-19 pandemic, and the subsequent recovery indicates that the pre-pandemic trajectory resumed rather than changed. Consistent with that interpretation, the annual volume of prescribing and the number of active prescribers both rose in every year after 2020. The increase in the number of distinct podiatrist prescribers, from roughly 2,600 to 5,600, further suggests that adoption, rather than intensification by a fixed group of prescribers, accounted for much of the growth.

The composition of prescribing, with ciclopirox retaining a dominant share despite the documented efficacy advantage of efinaconazole, deserves interpretation. Efinaconazole has superior nail penetration and higher mycological cure rates than ciclopirox, as shown in phase 3 trials and in pooled and post hoc analyses.(7,9,10) The relatively low share of the branded agents therefore does not reflect a lack of efficacy. In line with this, the persistence of ciclopirox is better explained by its long market presence, generic availability and low unit cost, and by its continued use in combination with oral therapy.(6) The modest uptake of the branded agents parallels the under-treatment reported in ambulatory surveys and the high frequency of potentially unnecessary topical prescriptions in commercial claims, findings that together indicate prescribing decisions are influenced by factors other than efficacy alone.(12,14) Guideline-adherence analyses reach a similar conclusion for diagnosis and treatment selection.(13) The acceleration of efinaconazole claims in the final years of the period is consistent with growing familiarity, long-term and maintenance regimens, and individualized use in diverse patient groups.(24,25) Tavaborole remained a smaller share than efinaconazole throughout, a pattern that parallels its narrower evidence base and less consistent adoption in clinical practice. The concentration of spending is nonetheless striking: efinaconazole alone accounted for most of the drug cost despite representing a small minority of claims, which explains why spending rose much faster than the number of prescriptions.

The clinical meaning of this composition is twofold. On one hand, the continued dominance of a generic with modest cure rates suggests that many treated patients receive a product with limited mycological efficacy, which may contribute to recurrence and repeated courses of care. On the other hand, the growth of efinaconazole use, particularly in its later years, indicates that a subset of prescribers adopted the more effective agent and that the barrier to broader use is more likely economic than scientific. The heterogeneity of topical response itself, which depends on nail thickness, the number of affected nails and the duration of disease, means that no single agent is appropriate for every patient and that treatment selection should be individualized rather than driven by default.(26-28)

These findings also bear on the interpretation of prescribing quality. The observation that treatment is prescribed at a minority of onychomycosis visits, together with the frequency of potentially unnecessary topical prescriptions identified in claims data, has been used to argue that both under-treatment and over-treatment coexist.(12,14) The present national series adds a third dimension: among podiatrists who do prescribe, the default choice is often the least effective topical, while the most effective and most costly agent is concentrated in a minority of states. Prescribing quality improvement therefore has to address not only whether a topical antifungal is given, but which one, and for whom.

The marked between-state variation in per-beneficiary cost and its strong correlation with the branded share indicate that drug mix, rather than volume alone, drives geographic differences in spending. This pattern is consistent with evidence that physician migration propagates prescribing styles across regions and with the substantial heterogeneity documented within Medicare Part D more generally.(29,30) It also mirrors specialty-level analyses of Medicare Part D that described national trends and geographic concentration in dentist prescribing of opioids and antibiotics.(31,32) In the present data, the states with the highest per-beneficiary costs were those in which branded agents represented the largest share of claims, whereas the lowest-cost states relied almost exclusively on ciclopirox. Because branded topical antifungals carry higher out-of-pocket costs for beneficiaries, this geographic pattern also implies unequal financial burden for otherwise similar patients depending on where they receive care, a consideration that is relevant to benefit design and to the transparency of prescribing choices.

The methodological approach adopted here mirrors a growing body of specialty-level analyses built on the same Medicare Part D public use files. Studies of dentist prescribing of opioids and of antibiotics used identical records to describe national trends and geographic concentration and found, as in the present analysis, that a specific drug mix and a limited set of states accounted for a disproportionate share of prescribing and spending.(31,32) The consistency across specialties suggests that the framework is generalizable and that the present findings reflect structural features of Part D prescribing rather than an idiosyncrasy of podiatry.

Several mechanisms plausibly account for these results. Spending grew faster than volume because the per-claim price of efinaconazole and tavaborole is substantially higher than that of ciclopirox, and that price gradient concentrates spending where branded adoption is greatest, in keeping with the role of specialty drugs in rising Part D drug prices.(33) The preference for topical therapy in older adults and in people with diabetes, driven by the avoidance of drug-drug interactions, sustains demand for these agents in the population most likely to use Medicare Part D.(5) Concerns about antifungal resistance and emerging dermatophyte issues may also favor topical options in selected patients.(34-37) The detection of squalene epoxidase mutations in United States patients with onychomycosis indicates that resistance to oral terbinafine is no longer a theoretical concern, which reinforces the clinical role of effective topical agents in patients who cannot take or fail oral therapy.(36) Finally, the clinical response to topical therapy is heterogeneous and depends on nail thickness, the number of affected nails and individual patient factors, which may contribute to the variability of use across prescribers and regions.(26-28)

The study has several strengths. It used a complete national census of Medicare Part D prescriber records over eleven years, restricted the analysis to a single specialty to isolate podiatrist behavior, and relied on open data with a documented and reproducible query, so the results can be independently recalculated. The use of three drugs within a single therapeutic class also limits the influence of indications unrelated to onychomycosis. The analytical plan was specified before the data were inspected, with three hypotheses defined in advance, each with a stated measure and decision criterion, which reduces the risk of selective reporting. Finally, the temporal coverage from the launch year of the branded agents to the most recent release provides the longest possible national view of adoption among podiatrists.

From a practical standpoint, the wide and drug-mix-driven variation in per-beneficiary costs points to opportunities for formulary management and for stewardship of topical antifungal prescribing, especially in view of the documented frequency of unnecessary topical prescriptions. For podiatrists, the sustained dominance of ciclopirox despite its lower efficacy, and the modest uptake of more effective branded agents, suggest that treatment selection in nail care pathways merits review. The results also provide a baseline against which the effect of generic efinaconazole entry and of Medicare drug price negotiation can be monitored in subsequent reporting years.

For payers and policymakers, the concentration of spending in a single branded product that accounts for a minority of prescriptions illustrates, on a small scale, the broader dynamics of specialty drug costs within Medicare Part D.(16,33) Because the three agents are close therapeutic substitutes within a single class, the observed interstate variation cannot be explained by differences in disease burden alone and is more plausibly driven by local prescribing culture, detailing, formularies and out-of-pocket design. Benchmarking state-level prescribing against the mix of the lowest-cost jurisdictions could therefore identify savings without reducing access, and the public availability of the underlying data makes such monitoring inexpensive and reproducible.(18)

For podiatric education and professional practice, the results suggest concrete content for continuing education and for clinical pathways in nail care. Clinicians should be familiar with the comparative efficacy of the three agents, with the predictors of poor topical response such as nail thickness and the number of affected nails, and with the circumstances under which a more expensive branded agent is justified by a higher likelihood of cure rather than by habit.(26,27) Because podiatrists are often the clinicians who establish the initial diagnosis and treatment plan, their choices shape both the clinical course and the cost borne by the Medicare program and by beneficiaries.

CONCLUSIONS

Topical antifungal prescribing by podiatrists in Medicare Part D increased substantially between 2014 and 2024 in claims, 30-day fills and drug spending, with spending growing faster than volume. The composition of prescribing shifted from ciclopirox toward efinaconazole and tavaborole, although ciclopirox remained the most prescribed agent throughout the period. Per-beneficiary drug costs varied widely across states and were strongly associated with the state share of branded agents, indicating that drug mix, rather than disease burden alone, is the main driver of geographic differences in spending and a target for stewardship and formulary policy.

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