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In the U.S., more than 90% of tinea capitis is caused by Trichophyton tonsurans; Microsporum canis infections are the minority. Worldwide, T. violaceum and M. audouinii are also prevalent. Terbinafine hydrochloride oral granules recently received FDA approval for pediatric tinea capitis in children aged 4 years and older. How does the new formulation compare with griseofulvin?
To find out, researchers enrolled children (age range, 4–12 years) from the U.S., Peru, Russia, and Egypt in a large, multicenter, randomized, investigator-blinded study. A clinical diagnosis of tinea capitis with positive potassium hydroxide (KOH) results but not necessarily a positive culture was required for inclusion. The children were randomized to receive terbinafine (5–8 mg/kg/day for 4 weeks; n=1040) or griseofulvin (10–20 mg/kg/day for 6 weeks; n=509). Dermatophytes varied, with T. tonsurans, T. violaceum, M. canis, and M. audouinii constituting the majority. Complete cure (clinical plus mycologic) rates were 45% with terbinafine versus 39% with griseofulvin (P<0.05). The clinical cure rates were 63% and 59%, respectively — not a significant difference. The granules, sprinkled on food, were easy to administer. Both agents had excellent safety profiles, without signs of laboratory abnormalities. The authors note that the varied distribution of infecting microorganisms was a limitation of this study. Griseofulvin was more effective than terbinafine against M. canis.
Elewski BE et al. Terbinafine hydrochloride oral granules versus oral griseofulvin suspension in children with tinea capitis: Results of two randomized, investigator-blinded, multicenter, international, controlled trials. J Am Acad Dermatol 2008 Jul; 59:41.
Comment
This is the largest study to date of terbinafine for pediatric tinea capitis. Cure rates were moderate, but, had results been stratified by infecting organisms and had griseofulvin doses matched standard practice (20 mg/kg/day vs. as little as 8.9 mg/kg/day in the lowest-weight patients), the cure rates might have been much higher. Unfortunately, FDA regulations prevent the use of the “nonapproved” higher griseofulvin dose as a control, which limits the utility of this and other head-to-head studies. The “mycologic cure” and “complete cure” rates are hard to interpret, given that 15% of patients in the griseofulvin arm and 18% in the terbinafine arm had negative cultures at entry. Nevertheless, terbinafine oral granules are a welcome addition to the armamentarium against pediatric tinea capitis. Future studies will determine which agent should be the first-line therapy for T. tonsurans tinea capitis.