Onychomycosis is caused most commonly by Trichophyton rubrum or T. mentagrophytes. About 10% of all persons worldwide and 40% of those ≥60 years old are believed to have the disease. Risk factors include older age, diabetes, poor peripheral circulation, smoking, HIV infection, psoriasis, and immunosuppression. Left untreated, onychomycosis can cause nail plate destruction, ingrown nails, and (particularly in patients with diabetes) secondary infections. Guidelines on treatment of onychomycosis have been published.

The FDA has approved a buccal tablet formulation of miconazole (Oravig – Strativa) for local treatment of oropharyngeal candidiasis in adults. Miconazole has been available for many years in topical formulations for treatment of superficial fungal infections and vulvovaginal candidiasis.

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Rifabutin (formerly ansamycin; Mycobutin - Adria), a rifamycin antibiotic similar to rifampin (Rifadin, Rimactane) was recently approved by the US Food and Drug Administration for prevention of disseminated Mycobacterium avium complex (MAC) disease in patients with advanced HIV infection.

Itraconazole (Sporanox - Janssen), an oral antifungal triazole that has been available in the USA since 1992 for treatment of deep fungal infections (Medical Letter, 35:7, 1993), is now being marketed for treatment of dermatophyte infections of the toenails, with or without fingernail involvement.

Voriconazole (Vfend -- Pfizer), an antifungal triazole structurally related to fluconazole (Diflucan) with a spectrum of action similar to that of itraconazole, has been approved by the FDA for primary treatment of invasive aspergillosis and for refractory infection with Scedosporium apiospermum (the asexual form of Pseudallescheria boydii) or Fusarium spp.

Terbinafine (Lamisil - Sandoz), an allylamine synthetic antifungal, previously available in the USA in a topical formulation (Medical Letter, 35:76, 1993) has now been marketed for oral use in the treatment of fungal nail infections caused by dermatophytes. Oral terbinafine has been available in Europe since 1992.

Fexofenadine (fex oh fen' a deen) hydrochloride (Allegra - Hoechst Marion Roussel) has been approved by the US Food and Drug Administration for treatment of seasonal allergic rhinitis. An active metabolite of terfenadine, fexofenadine is being heavily advertised as "nonsedating...without 'black box' warnings."

Celecoxib, a selective COX-2 inhibitor, has been approved by the FDA for treatment of osteoarthritis and rheumatoid arthritis.

Changes caused by one drug in the absorption, distribution, metabolism or excretion of another may lead to a pharmacokinetic adverse drug interaction (DN Juurlink et al, JAMA 2003; 289:1652). Additive drug interactions, such as vasodilation caused by both sildenafil (Viagra) and nitrates, can also have adverse effects.