Onychomycosis Treatment Guidelines

First-Line Oral Treatments

The British Journal of Dermatology recommends terbinafine as the first-line treatment for onychomycosis due to its superior efficacy, fungicidal properties, and favorable cost-effectiveness profile, with a strength of recommendation A and level of evidence 1+, and a dosage of 250 mg daily for 6 weeks for fingernails or 12 weeks for toenails 1, 2, 3
Terbinafine has a mechanism of action that inhibits squalene epoxidase, depleting ergosterol and accumulating squalene, which is directly fungicidal, and has side effects including headache, taste disturbance, gastrointestinal upset, and can aggravate psoriasis and cause lupus-like syndrome, with a contraindication of hepatic impairment 1, 2
Itraconazole is considered an alternative first-line treatment, with a dosage of 200 mg twice daily for 1 week per month, and two pulses for fingernails and three for toenails, and has better absorption with food and acidic pH, and contraindications including heart failure and hepatotoxicity 2, 3, 4

Griseofulvin is the least effective oral agent, with a mycological cure rate of 30-40%, and is only indicated when other agents are unavailable or contraindicated, and requires a longer treatment duration of 6-9 months for fingernails and 12-18 months for toenails 1, 4

Amorolfine 5% nail lacquer is effective in approximately 50% of cases when infection is limited to the distal portion of the nail, and has side effects including local burning, pruritus, and erythema 4, 1
Ciclopirox 8% nail lacquer has mycological cure rates of 34% vs 10% with placebo, and requires monthly removal of unattached, infected nail by a healthcare professional 1

The British Journal of Dermatology recommends terbinafine as the preferred treatment for diabetic patients due to its lower risk of drug interactions and hypoglycemia, and onychomycosis is a significant predictor for foot ulcers in diabetics 6
In immunosuppressed patients, most cases are due to T. rubrum, and terbinafine and fluconazole are preferred due to their lower risk of interactions with antiretrovirals 6, 7

Onychomycosis has high recurrence rates of 40-70%, and prevention strategies include wearing protective footwear in public facilities, using absorbent powders and antifungal powders in shoes, keeping nails short, avoiding sharing nail clippers, and considering discarding contaminated footwear or treating with naphthalene mothballs 7

Treatment failure may occur due to dense white lesions requiring mechanical removal, thick nails, severe onycholysis, and slow outgrowth, and poor compliance with lengthy treatment regimens 7, 5
Mycological resistance is a concern, with treatment failure in 25-40% of patients, and in vitro testing shows terbinafine and voriconazole are most potent against dermatophytes, and itraconazole and voriconazole are most active against yeast species 5