Onychomycosis Treatment: Are Topical Therapies Worthwhile?

Topical therapies are generally the least effective treatment option for nail bed fungal infections, also known as onychomycosis.

Onychomycosis is notoriously difficult to treat and cosmetically distressing. One in 4 patients don’t respond to therapy, and up to half of patients will experience relapse.

Beyond efficacy issues, treatment options for onychomycosis come with certain risks. A 3- to 6-month regimen of oral antifungals comes with hepatotoxicity risk and a host of drug interaction possibilities. Most notably, the azole antifungals inhibit the most prevalent and critical hepatic enzyme (CYP3A4) in drug metabolism.

Despite these interaction risks, oral therapy is more effective and takes up to 75% less time to complete than topical therapy. Cure rates for oral therapy fall between 45% to 70%, and total remission occurs for 35% to 80% of patients.

Topical therapy doesn’t come with the numerous drug-drug interactions of oral azole therapy. Adverse effects are limited to localized redness, swelling, and rashes. Most patients don’t experience relief from topical treatments, and the small subset of patients that do usually need courses as long as 12 months to see relief.

Another major disadvantage of topical therapy for onychomycosis is that only 0.1% of the drug is able to diffuse through the nail to the nail bed. However, penetration and cure can be aided by mechanical and chemical means.

Available topical agents include 8% ciclopirox and 25% undecylenic acid nail lacquers, 13% undecylenic acid cream, and 10% efinaconazole solution (Jublia by prescription only). Ciclopirox completely cures about 7% of patients and mycologically cures 29% to 36% of patients. Meanwhile, efinaconazole accomplishes complete cure for 15% to 18% of patients and mycologic cure for 54% of patients.

Mechanical methods, including nail abrasion and removal, reduce or eliminate the nail absorption barrier and remove fungal debris. Nail avulsion can be accomplished in a clinic setting with local anesthesia and urea or salicylic acid to soften the nail plate. These chemical nail softeners and organic solvents like ethanol, propylene glycol, and polyethylene glycol improve drug penetration through nails, as well.

Clinicians should advise patients to abide by the following recommendations from the Mayo Clinic to prevent infection, relapse, or reinfection of nail beds:

· Washing infected hands and/or feet regularly with soapy water, then drying thoroughly

· Keeping nails short, filed straight across, and without nail polish

· Wearing correctly-sized shoes and sweat-absorbing socks (eg, cotton, not nylon)

· Avoiding or wearing water-proof footwear in high-risk environments like public showers and around swimming pool