A very common, although not a life-threatening fungal infection of the nail, Onychomycosis is regarded as a serious health problem because of increasing global prevalence.
According to a study by P. Dyanne et al, Onychomycosis occurs in 10% of the general population but is more common in older adults; the prevalence is 20% in those older than 60 years and 50% in those older than 70 years. The increased prevalence in older adults is related to peripheral vascular disease, immunologic disorders, and diabetes mellitus.
Men are more affected by Onychomycosis as compared to women, according to a study titled ‘Onychomycosis: Diagnosis and management’.
Onychomycosis Therapeutic landscape
A patient suffering from Onychomycosis is a walking reservoir of the infection. There is always a risk of spreading the infection from untreated patients.
Upon diagnosis of Onychomycosis, a broad spectrum anti-fungal drug is prescribed which works to eliminate the fungus and keeping the patient safe. The drug is known to produce high cure rates with limited drug interactions and minimal to no side effects at economical rates.
In the onychomycosis treatment, the desired endpoints are a mycological, clinical, and complete cure. Onychomycosis treatment can be either topical, systemic, or a combination of both.
Oral antifungals used to treat onychomycosis include griseofulvin, azoles including ketoconazole, itraconazole and fluconazole, and allylamine terbinafine. However, the duration of the administration of the medication and the extent of the associated side effects prove to be a setback.
Talking about terbinafine (Lamisil), the drug is taken daily for 8 weeks for fingernail fungus and for 12 weeks for toenail fungus. Traconazole (Sporanox) is often prescribed in “pulse doses” one week per month for 2 or 3 months. It can interact with some commonly used drugs such as the antibiotic erythromycin or certain asthma medications. Griseofulvin (Fulvicin, Gifulvin, and Gris-Peg) has been the mainstay of oral antifungal therapy for many years. Although this drug is safe, it is not very effective against toenail fungus.
Despite the proven efficacy of oral antifungals, clinical outcomes are often far from satisfactory. In an attempt to improve the cure rate and reduce relapse, the use of combination therapy has become necessary.
Majority of the patients used to prefer oral drugs for onychomycosis. The onychomycosis therapeutics market is mainly dominated by terbinafine, however, due to lower efficacy, the use was limited. Talking about older onychomycosis patients with diabetes or peripheral neuropathy, they were more comfortable with itraconazole.
The combination of oral and topical drugs may allow a reduction in oral dosing resulting in increased patient tolerance and compliance while improving efficacy and reducing relapse. Itraconazole and amorolfine lacquer; oral terbinafine (transungual solution by polichem currently under Phase III trial for onychomycosis in various countries) and amorolfine lacquer were shown to be effective.
A new medicated nail lacquer has been approved to treat finger or toenail fungus that does not involve the white portion of the nail (lunula) in persons with normal immune systems. Currently used topical antifungals include ciclopirox 8% and amorolfine 5% lacquers. Both have a broad action spectrum against yeasts, dermatophytes, and NDM. Lacquers are specialized transungual drug delivery systems that produce a nonwater soluble film following application and evaporation of solvent which remains in contact with the nail for long. Kerydin (tavaborole) by Anacor Pharmaceuticals and (efinaconazole) by Valeant Pharmaceuticals are also approved for topical use.
However, Topical therapy should not be used if nail penetration is expected to be sub-optimal. Creams and other topical medications are usually not effective against nail fungus. This is because nails are too hard for external applications to penetrate.