Treatment options for onychomycosis

Onychomycosis is a common fungal infection of the nail and affects up to 8% of the general population. Therapy for infected nails takes months and is often ineffective or shows high recurrence rates. Current treatment options include: topical antifungal treatment, sometimes in addition to mechanical and chemical methods; systemic antifungal therapy; and device-based treatments. Topical creams like Ciclopirox 8% are ineffective for nails, although applied as a nail lacquer low cure rates can be achieved and they are safe for use. Systemic treatments, especially oral terbinafine, is effective but is in limited use owing to its interaction with other medications and liver toxicity. Laser irradiation of affected nails shows promising results, but needs to be further investigated on the best parameters related to type of fungus, nail involvement, and recurrence rates.

Onychomycosis is a chronic fungal infection of the toe or fingernail and is present in 50% of all nail disease cases¹. This condition affects 2–14% of the general population^2,3, and the number rises to 28% in populations above 60 years of age ⁴. Factors such as older age, psoriasis ⁵, immune system deficiency ⁶, diabetes ⁷, and smoking ⁸ predispose to nail fungal infections. Dermatophytes are responsible for 68% of onychomycosis cases, with the two most common species being Trichophyton rubrum and Trichophyton mentagrophytes ⁹. Fingernail fungal infection is more commonly associated with yeast infection ¹⁰.

Onychomycosis classification has evolved within the past year. Hay and Baran distinguish the following types ¹¹:

• Distal/lateral subungual onychomycosis (DLSO)
• Superficial white onychomycosis (SWO)
• Endonyx onychomycosis (EO)
• Proximal subungual onychomycosis (PSO)
• Mixed pattern onychomycosis (MPO)
• Total dystrophic onychomycosis (TDO)
• Secondary onychomycosis.

Onychomycosis reduces quality of life, with depression, anxiety, and avoidance of intimate relationships commonly reported¹². As many as 75% of patients report being embarrassed of their nails¹³. Low cure rates, high recurrence rates, and side-effects and limited indications of currently available systemic treatments push researchers to look for alternative therapies. These treatments need to be less expensive, safer, show improved response-to-treatment rates, and provide better patient compliance. Preliminary studies suggest that laser treatments might be an alternative.

As onychomycosis is hard to treat, it is paramount that physicians define ‘cure’. Scher et al defined the criteria for cure in onychomycosis as a 100% absence of clinical signs of onychomycosis or negative mycological laboratory results with less than 10% of visibly altered nail plate¹⁴.

However, other definitions include:

• Mycological cure = negative mycological test results
• Clinical cure = absence of visible nail plate lesions
• Complete cure = complete absence of infection and clinically and negative mycological laboratory results.

Such methodological inconsistencies make it difficult to compare results of clinical trials. In addition, any nail fungus therapy requires at least 6 months for the effects to be visible owing to nail regrowth (toenails need twice as much time). Studies have to monitor patients for a long time, which makes patient compliance difficult. It also makes the documentation of recurrence rates challenging, so at present no such data can be found.