Tinea Pedis Natural History

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Tinea PedisNatural HistoryClinical Trials

• Joseph Porres, M.D., Ph.D.
• Medical Officer, DDDDP

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Part I Natural History

• Tinea pedis subtypes
• Causative organisms
• Dermatomycosis syndrome
• Predisposing factors
• Complicating factors Complications
• Epidemiology recurrence
• Diagnosis
• Treatment

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Tinea Pedis Subtypes

• Interdigital pruritus, erythema, scaling,
  fissuring, maceration
• Plantar
• Moccasin scaling, pruritus, erythema
• Vesicobullous pruritus, vesicles, scaling,
  erythema
• Combinations of interdigital and plantar
• Athletes foot is the laymans term and can be
  found in reference to any of these forms

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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)

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Tinea Pedis Interdigitalis
Dermatlas, JHMI.EDU
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Tinea Pedis Plantaris
Rebell, G. Zaias, N. Cutis 2001, 67, 5S, 6-17
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Tinea Pedis Plantaris, Vesicular
Dermatlas, JHMI.EDU
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Tinea Pedis Plantaris, Moccasin
Rebell, G. Zaias, N. Cutis 2001, 67, 5S, 6-17
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Rebell, G. Zaias, N. Cutis 2001, 67, 5S, 6-17
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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

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Complicating Factors

• Immunosuppression
• Atopy
• Diabetes
• Compromised circulation
• Localized trauma
• Geriatric population

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Complications Cellulitis

• Tinea pedis unrecognized
• Treatment not given
• Treatment is inadequate
• Reinfection from the nail

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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

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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 32290-2

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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

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Study Results
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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

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Treatment. Efficacy rates reported
Treatment of Skin Disease. Lebohl, M. et al,
Mosby. 2003
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Part II Clinical Trials

• Dose ranging studies
• Clinical trials for safety and efficacy

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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

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Clinical Safety and Efficacy Trials

• Assessment
• Outcomes

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Assessment

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

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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

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Clinical Safety and Efficay Studies

• Inclusion/exclusion criteria often 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