Podiatrist Shares Onychomycosis Treatment Tips

LAS VEGAS — Onychomycosis, a stubborn fungal infection of the nail bed, is responsible for half of all nail diseases and presents a tricky challenge when it comes to both diagnosis and treatment.

According to Tracey C. Vlahovic, DPM, a professor at the Samuel Merritt University College of Podiatric Medicine, Oakland, California, most cases of onychomycosis are caused by the dermatophytes Trichophyton rubrum and Trichophyton mentagrophytes,although the causecan also be a mixed infection. “Dermatophytes are going to impact the nails first, and molds may come in and join the party later,” she said at the Society of Dermatology Physician Associates (SDPA) 22nd Annual Fall Dermatology Conference.

“The distal subungual onychomycosis (DSO) type is still the most common, but don’t forget that onychomycosis and nail psoriasis can happen at the same time. What we can’t lose sight of is that onychomycosis is a disease of the nail bed, which ultimately affects the nail plate; it’s not a disease of the nail plate first.”

Her diagnostic approach combines periodic acid-Schiff (PAS) staining with fungal culture “because I like to know the speciation,” she said. “PAS doesn’t give me the speciation; fungal cultures should. PCR can be expensive, but that can give me speciation.”

How Does This Happen?

DSO fungal onychomycosis occurs because of exposure to a dermatophyte, which can be as simple as tinea pedis. “Perhaps it’s the environment in the shoe,” said Vlahovic, one of the authors of a textbook on onychomycosis. “That’s something I’m always concentrating on with the patient. What is your foot hygiene like? What’s your shoe and sock wear? What’s your level of physical activity? You can have trauma to the hyponychium, where the skin and the nail meet. Maybe they trim their nails too close to the skin, or maybe there’s another skin condition like psoriasis.”

The dermatophyte, she continued, enters and invades the nail at the hyponychium and uses the keratinase enzyme to digest keratin in the nail bed. Mild inflammation develops, and pH changes cause focal parakeratosis and subungual hyperkeratosis in the form of onycholysis and subungual debris. “Hyphae then invades the lamina of the nail plate, which causes brittle nails,” she said. “The compromised hyponychium creates a reservoir for molds and bacteria.”

FDA-Approved Therapies

Therapies approved by the US Food and Drug Administration (FDA) for onychomycosis include the topical agents efinaconazole, tavaborole, and ciclopirox; the oral agents terbinafine and itraconazole; and laser therapy. Off-label, Vlahovic said that she sometimes uses oral fluconazole, pulsed dosing for terbinafine, and booster doses of terbinafine or any approved oral antifungal agent. Pulse dosing for itraconazole is FDA-approved for fingernails but not for toenails, she noted.

“We don’t have any oral antifungals that are approved for children, but we do have weight-based dosing,” she noted. Other off-label treatments for onychomycosis that patients may come across while browsing the internet but do not penetrate the nail plate, include products containing tolnaftate, tree oil, and undecylenic acid, “which is a very long-chain antifungal,” Vlahovic said. “It’s so huge that it can’t get through the nail plate. These products must get through the nail plate into the nail bed where the infection is.”

According to therapeutic recommendations for the treatment of toenail onychomycosis in the United States, published in 2021, terbinafine is the primary choice for oral treatment and efinaconazole 10% for topical treatment. There are no current treatment recommendations for pregnant or lactating patients. “I always defer to the obstetrician,” said Vlahovic, a co-author of the recommendations. For pediatric patients, she said, there are approved topical medications: Efinaconazole and tavaborole for ages 6 and up and ciclopirox for ages 12 years or older.

Treatment recommendations for adults vary based on clinical presentation and patient characteristics. Questions to consider: Are they older? Do they have diabetes? Are they able to reach their feet to apply medication? What other medications are they taking? Are there any kidney or liver issues that are cause for concern?

Another question to consider is whether they have concurrent nail psoriasis. “When I have those patients, I often treat the onychomycosis first and the nail psoriasis second,” she said.

Evidence for Lasers Weak

Though laser therapy is FDA-approved for the temporary increase of clear nails in onychomycosis, Vlahovic is underwhelmed by the evidence of its use for onychomycosis. According to a systematic review of 261 studies, only one reported treatment success as 16.7%, and clinical cures ranged from 13% to 16%. “Many of the existing studies were so poorly done in terms of protocols; it was frustrating,” she said. “No study has reported complete cure. There’s a lack of standardization across laser companies and a lack of standardization across protocols.”

Before starting oral antifungal therapy, Vlahovic uses the Onychomycosis Severity Index to determine the number of nails involved and the proportion of nails that are affected. She also wants to know if the patient is taking any medication that might interfere with an oral antifungal and gets baseline liver function tests (LFTs) to document results in the chart. “You want to discuss the pros and cons of oral antifungal therapy, and you want to set realistic expectations,” she added. “These medications are not cosmetic products; they are meant to kill fungus. Sometimes patients lose sight of that.”

Vlahovic routinely offers pulse dosing of terbinafine, which is FDA-approved at a dose of 250 mg/d for 90 days. Pulse dosing involves taking terbinafine 250 mg twice a day for 1 week, followed by a 3-week break. This cycle is repeated three or four times. A clinical trial found no significant difference in outcome between patients who received pulsed vs continuous terbinafine dosing for the treatment of dermatophyte onychomycosis.

What About Oral Antifungal Safety?

For patients who ask about the safety of oral antifungals, Vlahovic characterized them as “well tolerated and safe in an immunocompetent population.” In a meta-analysis of 122 studies of about 22,000 patients, the pooled risk for treatment discontinuation because of adverse events was 3.4% for terbinafine 250 mg/d and 4.21% for itraconazole 200 mg/d. The risk for liver injury requiring termination of treatment and the risk of having symptomatic elevation of LFTs were less than 2% for all regimens.

According to the best available published evidence, Vlahovic said, the onychomycosis recurrence rate ranges from 6% to 40%. “That’s a wild number,” she said. “We really have no idea what the true recurrence rate is, and that’s a problem.”

Vlahovic disclosed having been a consultant to and an investigator for Ortho Dermatologics and Sagis Diagnostics.