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Tinea Pedis Natural History & Clinical Trials

Tinea Pedis Natural History & Clinical Trials. Joseph Porres, M.D., Ph.D. Medical Officer, DDDDP. Part I: Natural History. Tinea pedis subtypes Causative organisms Dermatomycosis syndrome Predisposing factors Complicating factors & Complications Epidemiology & recurrence Diagnosis

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Tinea Pedis Natural History & Clinical Trials

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  1. Tinea PedisNatural History&Clinical Trials Joseph Porres, M.D., Ph.D. Medical Officer, DDDDP

  2. Part I: Natural History • Tinea pedis subtypes • Causative organisms • Dermatomycosis syndrome • Predisposing factors • Complicating factors & Complications • Epidemiology & recurrence • Diagnosis • Treatment

  3. Tinea Pedis Subtypes • Interdigital: pruritus, erythema, scaling, fissuring, maceration • Plantar: • Moccasin: scaling, pruritus, erythema • Vesicobullous: pruritus, vesicles, scaling, erythema • Combinations of interdigital and plantar • Athlete’s foot is the layman’s term and can be found in reference to any of these forms

  4. Causative Organisms • Trichophyton rubrum (60-80%) • Plantar, mocassin • Plantar small vesicles, may also affect distal subungual nail, other body sites • Trichophyton mentagrophytes (10-20%), • Peri-plantar large vesicles, and may spread to white superficial nail • Epidermophyton floccosum (3-10%)

  5. Tinea Pedis Interdigitalis Dermatlas, JHMI.EDU

  6. Tinea Pedis Plantaris Rebell, G. & Zaias, N. Cutis 2001, 67, 5S, 6-17

  7. Tinea Pedis Plantaris, Vesicular Dermatlas, JHMI.EDU

  8. Tinea Pedis Plantaris, Moccasin Rebell, G. & Zaias, N. Cutis 2001, 67, 5S, 6-17

  9. Rebell, G. & Zaias, N. Cutis 2001, 67, 5S, 6-17

  10. Predisposing Factors • Closed communities: army barracks, boarding schools • Public baths, swimming pools • Local trauma on dermatophyte carrying individual • Occlusive footgear • Immersion • Warm weather • Exposure to hair of infected animals (rats in Vietnam) • Infected family members (~17% in one study) • Familial predisposition

  11. Complicating Factors: • Immunosuppression • Atopy • Diabetes • Compromised circulation • Localized trauma • Geriatric population

  12. Complications: Cellulitis • Tinea pedis unrecognized • Treatment not given • Treatment is inadequate • Reinfection from the nail

  13. Epidemiology • 15-70 % of population at large • 40 % of patients attending a general clinic • Those seeking help often have nail involvement • Many undiagnosed cases • Dermatophytes isolated from: • 2-40% “normal feet” • Public showers • Swimming pools • Shoes and Socks

  14. Recurrence Topical terbinafine and clotrimazole in interdigital tinea pedis: A multicenter comparison of cure and relapse rates with 1- and 4- week treatment regimens. Bergstresser PR et al, JAAD 1993; 28: 648-51 Long-term outcome of patients with interdigital tinea pedis treated with terbinafine or clotrimazole. Elewski, B. et al. JAAD 1995; 32:290-2

  15. Study Details • 193 evaluable patients with interdigital tinea pedis • Treatment twice daily with: • terbinafine cr or clotrimazole cr • 1 or 4 weeks Observation for up to 18 months [Elewski] • Mycology “Cure”

  16. Study Results

  17. Diagnosis • Clinical: by clinical signs and symptoms • Mycology: KOH (direct examination) and culture. • Mycology [KOH] helps confirm diagnosis and avoid: • Delay of indicated treatment • Prescribing inappropriate treatment

  18. Treatment. Efficacy rates reported*: * Treatment of Skin Disease. Lebohl, M. et al, Mosby. 2003

  19. Part II: Clinical Trials • Dose ranging studies • Clinical trials for safety and efficacy

  20. Dose Ranging Studies For Tinea Pedis • Dose ranging studies for topical antifungals often recommended by FDA but usually not conducted • Dose ranging studies for topical antifungals to select the best safety/efficacy dose: • Drug strength • Frequency of application • Duration of treatment

  21. Clinical Safety and Efficacy Trials • Assessment • Outcomes

  22. Assessment • Mycology: • Direct microscopic examination (KOH) • Mycology culture • Clinical. Signs and symptoms: • Erythema • Scaling • Pruritus, etc.

  23. Outcomes • Mycology “Cure” (MC): • Negative KOH and negative culture • Effective treatment: • MC, no symptoms, only residual signs • Complete Cure: • MC, and no signs or symptoms

  24. Clinical Safety and Efficay Studies Inclusion/exclusion criteriaoften do not mimic the populations expected to actually use the product • Include: healthy patients with interdigital tinea pedis • Exclude harder cases: • Onychomycosis • Mocassin type, keratotic feet • Diabetic • Immunosuppressed • Compromised circulation

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