Onychomycosis Treatment in the United States

Discussion

Onychomycosis is a common progressive infection of the nails that is more prevalent in older age groups, with equal prevalence in both genders and a higher prevalence in males. The NAMCS data showed higher rates of onychomycosis visits among older age groups, which is in agreement with results from prior studies.^16,17 In the current study, we observed a higher prevalence of onychomycosis visits among females as well as white and Hispanic patients. These results may be due to a higher prevalence of onychomycosis in these populations or simply a result of difference in socioeconomic level or importance of aesthetics. Although there are limited data regarding the prevalence of onychomycosis among different races and ethnicities in the United States, a high incidence of onychomycosis has been reported in Mexico.¹⁸

Repeated trauma to the great toenail from ill-fitting shoes is a predisposing factor for onychomycosis.¹⁶ In the current study, ingrown nails were among the most common comorbidities found in onychomycosis patients. Although nail dystrophy caused by onychomycosis may lead to ingrown nails, it also is possible that both conditions may be caused by trauma.

Patients with immunodeficiencies (eg, diabetes) may be predisposed to onychomycosis as well as its associated complications and morbidities (eg, cellulitis).^16,19 Diabetes affects 4% to 22% of patients with onychomycosis in different populations, including Denmark, Mexico, and India.^18,20,21 In our study, diabetes was among the most common recorded comorbidities reported during onychomycosis visits, with a prevalence of 3.4%. It is likely that many more visits involved patients with diabetes that had not been diagnosed or reported. With the increased risk for complications with diabetes, it is important for physicians to treat these patients when they have a nail infection.

The available systemic therapies for treatment of onychomycosis include griseofulvin, allylamines, and imidazoles. Comparison of griseofulvin with newer systemic antifungal agents such as terbinafine and itraconazole suggests that griseofulvin has lower efficacy and therefore is not a first-line treatment of onychomycosis.¹ Terbinafine is the most active of the currently available antidermatophyte drugs both in vitro and in vivo, with synergistic effects with imidazoles and ciclopirox.^1,22-27 A combination of topical and systemic therapies may improve cure rates of onychomycosis or possibly shorten the duration of therapy with the systemic agent.^1,2 Treatment strategies can vary according to the specialty of the treating physician, with general practitioners often preferring monotherapies and dermatologists preferring combination therapies.²⁸ In Europe, the most commonly prescribed medication for onychomycosis was topical amorolfine followed by systemic terbinafine and itraconazole.²⁸ In the current study, we could not separate data for topical versus systemic terbinafine because the NAMCS uses similar names for reporting the drug; however, the rates of prescription for allylamines and imidazoles were nearly equal (Figure 5), with terbinafine showing an increased use over time as opposed to a decreased use of imidazoles. Although fluconazole is not approved by the US Food and Drug Administration for treatment of onychomycosis, oral fluconazole was the second most common treatment prescribed in our study. Griseofulvin, which is not considered as a drug of choice in onychomycosis,¹ was prescribed in a small fraction of the visits, with a decreasing trend of usage over time.

Conclusion

Our analysis of the NAMCS data revealed that the treatment of onychomycosis in the United States is in accordance with recommendations in current guidelines. An encouraging finding was the notable downward trend in use of griseofulvin, suggesting that health care providers are changing practice to meet standard of care. Increased efforts must be made to uniformly modify practices in compliance with evidence-based recommendations and to minimize unnecessary risk and cost associated with use of drugs with lower efficacy.