Treating Tinea Pedis In Patients With Diabetes
Can Topical Therapies Have An Impact?
Given the potential drug interactions and side effects of oral itraconazole and oral terbinafine, topical therapies are sometimes preferable over these oral antifungal agents, especially for people with diabetes. Since topical ointments act locally, have low systemic absorption and any drug that the body absorbs metabolizes rapidly, there is less potential for adverse side effects and drug interactions.27,28 Furthermore, since many topical treatments (such as ciclopirox 8%) metabolize by glucuronidation, interactions with medications that metabolize via the P-450 system are unlikely.27,29
Another benefit of topical therapy is that many topical agents have broad spectrum antimicrobial properties and research has shown them to be effective against dermatophytes, yeasts and non-dermatophyte molds.30
Assessing The Shortcomings In The Literature
While there are many antifungal treatment options available, many of which have undergone study in otherwise healthy people, few studies have been conducted to determine the safety and efficacy of these treatment interventions in people with diabetes.
A recent systematic literature review that aimed to determine the safety and/or efficacy of treatment interventions for tinea pedis and onychomycosis in people with diabetes identified only six different studies.31 From these studies, only three treatment interventions (oral itraconazole, oral terbinafine, topical ciclopirox 8%) underwent scrutiny and all were for the treatment of onychomycosis. Currently, there does not appear to be any evidence for the safety and efficacy of treatment interventions for tinea pedis in people with diabetes.
Current evidence suggests both oral terbinafine and oral itraconazole therapy are superior (in terms of safety and efficacy) to topical ciclopirox 8% therapy for the treatment of onychomycosis in people with diabetes.31 There is also good (level II) evidence to suggest that oral terbinafine is as safe and effective as oral itraconazole for the treatment of onychomycosis in people with diabetes.20
However, we cannot generalize the results of these studies to all people with diabetes as studies included in this review were limited by a small sample size and had threats to external validity. Some participants, for example, were not taking any medications known to interact with antifungal agents. Thus, clinical judgment remains critical when prescribing medications.
Pertinent Insights On Combination Therapy
Complete cure of tinea pedis is a lengthy process for people both with and without diabetes. According to studies that examine treatment interventions for people with diabetes, complete cure only occurs for 7 to 50 percent of people after approximately 48 weeks since the beginning of treatment with oral itraconazole or oral terbinafine.31 This is a considerable length of time for a patient who may be at an increased risk of developing a foot ulcer.
There is also a significant number of patients who are never cured during this period of time but still have the expense of treatment and have also possibly incurred the side effects of the medications.