Chapter 053. Eczema and Dermatitis (Part 11)

Dermatophytosis: Treatment Both topical and systemic therapies may be used to treat dermatophyte infections. Treatment depends on the site involved and the type of infection. Topical therapy is generally effective for uncomplicated tinea corporis, tinea cruris, and limited tinea pedis. It is not effective as a monotherapy for tinea capitis or onychomycosis. Topical imidazoles, triazoles, and allylamines may be effective therapies for dermatophyte infections, but nystatin is not active against dermatophytes. Topicals are generally applied twice daily, and treatment should continue 1 week beyond clinical resolution of the infection. Tinea pedis oftenrequires longer treatment courses and frequently relapses. Oral...
Nội dung trích xuất từ tài liệu:
Chapter 053. Eczema and Dermatitis (Part 11) Chapter 053. Eczema and Dermatitis (Part 11) Dermatophytosis: Treatment Both topical and systemic therapies may be used to treat dermatophyteinfections. Treatment depends on the site involved and the type of infection.Topical therapy is generally effective for uncomplicated tinea corporis, tineacruris, and limited tinea pedis. It is not effective as a monotherapy for tinea capitisor onychomycosis. Topical imidazoles, triazoles, and allylamines may be effectivetherapies for dermatophyte infections, but nystatin is not active againstdermatophytes. Topicals are generally applied twice daily, and treatment shouldcontinue 1 week beyond clinical resolution of the infection. Tinea pedis oftenrequires longer treatment courses and frequently relapses. Oral antifungal agentsmay be required for recalcitrant tinea pedis or tinea corporis. Oral antifungal agents are required for dermatophyte infections involvingthe hair and nails and for other infections unresponsive to topical therapy. Afungal etiology should be confirmed by direct microscopic examination or byculture prior to prescribing oral antifungal agents. All of the oral agents may causehepatotoxicity and should not be used in women who are pregnant or breast-feeding. Griseofulvin is the only oral agent approved in the United States fordermatophyte infections involving the skin, hair, or nails. When griseofulvin isused, a daily dose of 500 mg microsized or 375 mg ultramicrosized griseofulvinadministered with a fatty meal is an adequate dose for most dermatophyteinfections. Higher doses are required for some cases of tinea pedis and tineacapitis. The usual adult dose of griseofulvin for tinea capitis is 1 g microsized or0.5 g ultramicrosized given daily. Markedly inflammatory tinea capitis may resultin scarring and hair loss, and systemic or topical glucocorticoids may be helpful inpreventing these sequelae. The duration of therapy may be 2 weeks foruncomplicated tinea corporis, 8–12 weeks for tinea capitis, or as long as 6–18months for nail infections. Due to high relapse rates, griseofulvin is seldom usedfor nail infections. Common side effects of griseofulvin include gastrointestinaldistress, headache, and urticaria. Oral itraconazole and terbinafine are approved for onychomycosis.Itraconazole is given as either continuous daily therapy (200 mg/d) or pulses (200mg bid for 1 week per month) administered with food. Fingernails require 2months of continuous therapy or two pulses. Toenails require 3 months ofcontinuous therapy or three pulses. Itraconazole has the potential for seriousinteractions with other drugs requiring the P450 enzyme system for metabolism.Terbinafine (250 mg/d) is also effective for onychomycosis. Therapy withterbinafine is continued for 6 weeks for fingernail infections and 12 weeks fortoenail infections. Terbinafine has fewer drug-drug interactions, but cautionshould be used when patients are on multiple medications. Tinea Versicolor Tinea versicolor is caused by a non-dermatophyte, dimorphic fungus,Malassezia furfur, a normal inhabitant of the skin. The expression of infection ispromoted by heat and humidity. The typical lesions consist of oval scaly macules,papules, and patches concentrated on the chest, shoulders, and back but only rarelyon the face or distal extremities. On dark skin, they often appear ashypopigmented areas, while on light skin, they are slightly erythematous orhyperpigmented. A KOH preparation from scaling lesions will demonstrate aconfluence of short hyphae and round spores (spaghetti and meatballs). Lotionsor shampoos containing sulfur, salicylic acid, or selenium sulfide will clear theinfection if used daily for 1–2 weeks and then weekly thereafter. Thesepreparations are irritating if left on the skin for more than 10 min; thus, theyshould be washed off completely. Treatment with some oral antifungal agents isalso effective, but they do not provide lasting results, and they are not FDA-approved for this indication. Ketoconazole has been used as a single 400-mg dose;the patient waits 1 h, exercises to the point of sweating, then lets the skin dry.Itraconazole and fluconazole have also been used at various doses and frequencies.Griseofulvin is not effective, and terbenifine is not reliably effective for tineaversicolor. Candidiasis Candidiasis is a fungal infection caused by a related group of yeasts, whosemanifestations may be localized to the skin, or rarely, may be systemic and life-threatening. The causative organism is usually Candida albicans, but may also beC. tropicalis, C. parapsilosis, or C. krusei. These organisms are normalsaprophytic inhabitants of the gast ...