What are the causes and treatments of onychomycosis (fungal infection of the fingernails)?

From the Guidelines

Fingernail fungus, medically known as onychomycosis, is best treated with oral prescription medications such as terbinafine (Lamisil) 250mg daily for 6 weeks, as it has been shown to be more effective than itraconazole in treating dermatophyte onychomycosis 1. When considering treatment options, it's essential to weigh the effectiveness, potential side effects, and patient-specific factors.

• For mild cases, topical antifungal solutions like Ciclopirox (Penlac) nail lacquer or over-the-counter options containing undecylenic acid or tea tree oil can be applied daily to clean, dry nails for several months.
• For more severe infections, oral prescription medications such as terbinafine (Lamisil) 250mg daily for 6-12 weeks or itraconazole (Sporanox) 200mg twice daily for one week per month, for 2-3 months, are more effective as they reach the nail bed through the bloodstream. While treating the infection, it's crucial to keep nails short, dry, and clean, wear breathable footwear, and avoid sharing nail tools.
• Treatment requires patience as complete nail regrowth takes 6-12 months for fingernails.
• The fungus thrives in warm, moist environments and enters through tiny cracks in the nail or surrounding skin, with the infection gradually causing nails to become discolored, thickened, brittle, and sometimes painful. People with diabetes or compromised immune systems should consult a doctor promptly as they face higher risks of complications 1. According to the British Association of Dermatologists' guidelines for the management of onychomycosis 2014, terbinafine is generally preferred over itraconazole due to its higher efficacy and lower risk of side effects 1. It's also important to note that topical therapy, such as amorolfine (Loceryl) nail lacquer, can be effective in around 50% of cases of both fingernail and toenail infection, but its use is limited to infections of the distal portion of the nail 1. Overall, the choice of treatment should be based on the severity of the infection, patient-specific factors, and the potential risks and benefits of each treatment option 1.

From the FDA Drug Label

Terbinafine tablets, USP are indicated for the treatment of onychomycosis of the toenail or fingernail due to dermatophytes (tinea unguium). Ciclopirox Topical Solution, 8%, (Nail Lacquer), as a component of a comprehensive management program, is indicated as topical treatment in immunocompetent patients with mild to moderate onychomycosis of fingernails and toenails without lunula involvement, due to Trichophyton rubrum

Treatment Options for Fingernails Fungus:

• Terbinafine (PO): indicated for the treatment of onychomycosis of the fingernail due to dermatophytes 2
• Ciclopirox (TOP): indicated as topical treatment for mild to moderate onychomycosis of fingernails without lunula involvement, due to Trichophyton rubrum 3

From the Research

Fingernails Fungus Overview

• Fingernails fungus, also known as onychomycosis, is a common fungal infection of the nail unit, accounting for roughly 50% of all nail disease 4.
• Approximately 90% of toenail and 75% of fingernail onychomycosis are caused by dermatophytes, notably Trichophyton mentagrophytes and Trichophyton rubrum 5.

Diagnosis and Treatment

• The diagnosis of onychomycosis can be confirmed by direct microscopic examination with a potassium hydroxide wet-mount preparation, histopathologic examination of the trimmed affected nail plate with a periodic-acid-Schiff stain, fungal culture, or polymerase chain reaction assays 5.
• Oral terbinafine is the treatment of choice, followed by oral itraconazole, while topical monotherapy can be considered for mild to moderate onychomycosis 5.
• Combining oral and topical antifungal drugs is associated with higher success rates, and additive or synergistic modes of action are expected to enhance treatment success rates 6.

Treatment Options

• Oral antifungal therapies, such as terbinafine and itraconazole, are effective but may have significant adverse effects 5, 7.
• Topical antifungal therapies have minimal adverse events but are less effective due to poor nail penetration 5.
• Combination therapy and device-based treatments may enhance cure rates, and further study is required 4.
• The use of oral antifungal agents, such as terbinafine, in immunocompromised patients is supported by limited data, and these agents appear to be safe, with a relatively low potential for drug-drug interactions 7.