Rapid Treatment of Subungual Onychomycosis Using Controlled Micro Nail Penetration and Terbinafine Solution
August 2016 | Volume 15 | Issue 8 | Original Article | 974 | Copyright © August 2016
Ivan Bristow PhD,a Robert Baran MD,b and Michelle Score BSc (Hons)c
aFaculty of Health Sciences, University of Southampton, UK
bNail Disease Centre, Cannes, France
cThe Chiropody Surgery, Lymington, UK
Onychomycosis continues to be a common and intractable problem in adults, often responding poorly to topical treatment due to limited drug penetration of the nail plate. Improving penetration has been attempted previously by chemical and physical means with some success. The authors present three cases of toenail onychomycosis treated topical terbinafine 1% solution using controlled micro-penetration of the nail using a novel intelligent nail drill system which is able to drill nail plate without penetrating the delicate nail bed beneath. The cases illustrate how the device has been successfully employed to deliver the anti-fungal drug directly and rapidly to the site of infection with minimal side effects or complications, whilst maintaining the nail integrity. J Drugs Dermatol
Onychomycosis continues to be a common and intractable problem in adults, often responding poorly to drug treatment. Toenails are most frequently affected by the infection, particularly the hallux.1 Studies suggest its prevalence to be around 29% across Europe,2 showing an increase in prevalence with age3 and in countries with longer winters. The causative agents are typically the dermatophyte species of fungi which spread from plantar skin over many months to invade the nails through a distal and lateral subungual route producing the characteristic discolouration of the nail plate.4 Over many months, complete invasion of the nail may lead to total dystrophy. Onychomycosis is often trivialised as a cosmetic condition but studies have confirmed its effect on the patient’s wellbeing and quality of life.5-7 Moreover, the presence of fungus on the foot is a risk factor for the development of lower limb cellulitis8 – a particular risk for patients with peripheral vascular disease and diabetes who have an increased propensity for the disease.9
Management of the condition to date has proved challenging. Oral systemic agents such as terbinafine and itraconazole have shown good mycological cure rates when taken over a number of months.10 However, potential side effects, drug interactions and reluctance from some patients to oral medications remains a limitation. Exploring new techniques, the use of lasers has been suggested and reported as a less invasive and safer technology to destroy the subungual infection by rapid heating of the infected area. However, results have suggested that it has little evidence to date to support their widespread use in onychomycosis.11
Topical treatments, applied directly to the nail plate, have also been used widely but consistently have been shown to be less effective than the systemic drug regimes. The nail plate is naturally a barrier to drug penetration,12 effectively shielding the subungual area so the underlying infection remains protected. In addition, patients are expected to apply the medicament to the nail for many months. Studies of topical medicament usage have shown that compliance decreases the longer the treatment continues,13 which may result in a treatment failure.
Measures designed to enhance topical drug delivery have been trialled with some success. Chemical penetration enhancers have been developed and incorporated into many topical drugs to boost delivery of the active ingredient through the nail. Combination therapy – utilising a dual approach using concurrent topical and oral antifungals medications – has also been shown to improve overall cure rates.14
Topically, nail reduction by mechanical thinning of the nail has shown to modestly improve the clinical response to antifungal agents.15 Recently, researchers have employed the use of fractional lasers to penetrate the full thickness of nail plate to create a porous structure, thus allowing the easier passage of any applied antifungal.16 Fractional lasers concentrate power to a very small area, thus reducing the risks of thermal damage to peripheral tissue. This work is ongoing, with potential promise, but the expense of such systems is still prohibitive for general podiatric use. In addition, as with most “hot” lasers, pain appears to be a commonly reported side effect of the treatment with a risk of damage to the delicate subungual tissues.