Treating Tinea Pedis In Patients With Diabetes

Lisa Matricciani, RN, and Sara Jones, PhD, MSc, BA, DipAppSci

Patients with diabetes face a higher risk of tinea pedis, which can lead to complications, and research is scarce on the efficacy of medications in diabetic patients with the fungal condition. Accordingly, these authors provide a closer look at treatment and prevention strategies for tinea pedis, which often occurs in concert with onychomycosis.

   Tinea pedis is a contagious fungal infection that affects the feet of approximately 15 to 20 percent of the population, similar to onychomycosis.1-3 In comparison to otherwise healthy individuals, people with diabetes are at an increased risk of developing antifungal infection and are also more likely to face adverse complications including secondary bacterial infections, foot ulcers, paronychias, cellulitis, osteomyelitis, gangrene and lower limb amputation.4-8 Safe and effective treatment of tinea pedis is therefore imperative for people with diabetes.

   Tinea pedis commonly presents as red, itchy scales on the skin in between the toes and/or the soles of the feet. Often, but not always, tinea pedis presents alongside onychomycosis, causing the toenails to become thick, yellow and brittle. Since these conditions are contagious, without proper treatment, the infection may spread to both feet and all toenails.

   While tinea pedis can be uncomfortable and cosmetically displeasing, it is unlikely to cause any serious adverse complications in otherwise healthy individuals. For people with diabetes, however, the presence of this infection can lead to secondary bacterial infections, foot ulceration, paronychia, cellulitis, osteomyelitis, gangrene and possible lower limb amputation.4-8

   Tinea pedis may lead to foot ulceration through the development of skin fissures in the plantar and/or interdigital skin. Onychomycosis, on the other hand, may lead to foot ulceration as a result of a thick, sharp, brittle piece of nail piercing the skin or as a result of vascular compromise arising from increased subungual pressure due to enlarged nails. In both cases, injury creates a portal of entry for pathogens, which promotes the development of further complications.

   Unlike otherwise healthy individuals, people with diabetes are at an increased risk of developing these complications as they often present with some degree of peripheral neuropathy, retinopathy, obesity, elevated blood sugar levels and/or impaired immune function, which prevents them from recognizing, responding and recovering from injuries.9-12

   Accordingly, while people with diabetes are already at an increased risk of foot ulceration, infection and lower limb amputation, the presence of tinea pedis and/or onychomycosis may further increase their risk of developing such complications. Indeed, studies have shown that people with diabetes and onychomycosis have a significantly higher rate of foot ulceration, gangrene and a combination of foot ulcer and gangrene in comparison to people with diabetes but without onychomycosis.12,13

Key Treatment Considerations

In a Cochrane Review, Bell-Syer and colleagues sought to assess the effects and costs of oral treatment interventions for tinea pedis in otherwise healthy individuals.14 They found that terbinafine (Lamisil, Novartis) is more effective than griseofulvin (Grifulvin, Pedinol Pharmacal) therapy. They also noted no significant differences in efficacy between oral itraconazole (Sporanox, Janssen Pharmaceuticals) and oral terbinafine.

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