Clinical Inquiries

What is the best way to treat tinea cruris?

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EVIDENCE-BASED ANSWER

After clinical diagnosis and microscopic confirmation, tinea cruris is best treated with a topical allylamine or an azole antifungal (strength of recommendation: A, based on multiple randomized controlled trials [RCTs]). Differences in current comparison data are insufficient to stratify the 2 groups of topical antifungals. Determining which group to use depends on patient compliance, medication accessibility, and cost. The fungicidal allylamines (naftifine and terbinafine) and butenafine (allylamine derivative) are a more costly group of topical tinea treatments, yet they are more convenient as they allow for a shorter duration of treatment compared with fungistatic azoles (clotrimazole, econazole, ketoconazole, oxiconazole, miconazole, and sulconazole).

CLINICAL COMMENTARY

Choice of treatment should reflect cost and convenience to the patient
Dan Hunter-Smith, MD
Adventist LaGrange Family Medicine Residency, LaGrange, Ill

This review illustrates that the “best way” to treat a problem can have more to do with the needs of a given patient than intrinsic differences between treatments. All reviewed treatments were roughly therapeutically equivalent and equally safe. This leaves the choice of treatment to reflect the importance of cost and convenience to the patient. If cost is an issue for the patient, the frugal way to treat tinea cruris is to have the patient go to the vaginitis treatment section of the pharmacy and pick up a 15-g tube of miconazole or clotrimazole cream for $7 to $10. Terbinafine cream or spray costs $10 to $13 over the counter, but it reduces the onus of compliance to once-a-day for 1 week. If terbinafine 1% solution is preferred, a 30-mL bottle costs $77. Most of the time, I let the patient make their own choice.

Evidence summary

Tinea cruris (“jock itch”) is a superficial dermatophyte infection of the groin and surrounding skin. Obese adult men are affected more than women, and it is rarely seen in children. Because excessive perspiration is the most common predisposing factor, patient education on proper hygiene makes intuitive sense for successful treatment, yet it has not been studied.1Trichophyton rubrum is the most common source of tinea cruris, as well as tinea corporis (“ringworm”), in the United States.2 Most studies involving patients with tinea cruris combine data with tinea corporis.

Although more than 25 RCTs document the safety and efficacy of antifungal treatments, few head-to-head trials are available. Several topical preparations are approved for the treatment of tinea cruris. Selection should be based on patient compliance (duration of treatment), overall cost, and tolerability. The 2 main classes of antifungals are allylamines and azoles.

Allylamines. Allylamines offer a shorter duration of therapy, lower relapse rates, and work independent of the cytochrome P450 system. Multiple RCTs have documented the efficacy and safety of the 2 available allylamine antifungals, terbinafine and naftifine, when compared with placebo and various azoles.

Terbinafine is available in several 1% formulations (emulsion-gel, cream, and solution/spray), all studied and dosed once daily for 1 week. One placebo controlled trial showed the 1% emulsion-gel version (Lamisil) was effective in 89% of the study population vs 23% of the placebo group (NNT=1.5); it was particularly suitable on hairy skin. Seven weeks post-treatment, 84% of the intent-to-treat population of the Lamisil group remained mycologically negative.3 Data combined from 2 other RCTs yielded 83% efficacy 3 weeks post-treatment when 66 patients were treated with terbinafine 1% cream, compared with 12% efficacy for 73 patients using the vehicle cream (NNT=1.4).4 Another placebo-controlled study of 66 patients demonstrated 100% microscopic cure of terbinafine 1% solution by week 2 and maintaining 90% cure at 4 weeks.5

In a multicenter, double-blind RCT funded by the manufacturers of terbinafine, bifonazole 1% cream for 3 weeks was compared with terbinafine 1% cream used daily for 1 week (followed by 2 weeks of its vehicle cream). Mycological and clinical cure rates were greater than 95% in both groups at 3 weeks. At the 8-week follow-up, no statistically significant differences were seen in KOH positivity rates (20.24% of patients in the bifonazole-treated group were KOH-positive vs 11.76% in the terbinafine group). Symptom relapse rates at 8 weeks were not available.6

In a 4-week study involving 104 patients, naftifine 1% cream (Naftin) was compared with econazole 1% cream (Spectazole) (both applied twice daily). At the end of the study, naftifine 1% cream had a higher (but not statistically significant) mycological and clinical cure rate of 78% compared with 68% with econazole 1% cream.7 Similar results (79% mycological cure) were seen in a placebo-controlled trial with 70 patients using once daily naftifine 1% cream after 2 weeks of treatment (NNT=2).8

Butenafine (Mentax), a benzylamine antifungal, was 88% to 93% mycologically effective in a noncomparative study, when used twice daily for 2 weeks.9 Similar results were found in a study of 76 patients with tinea cruris; after 2 weeks of daily application, 78% (modified intent-to-treat group) were mycologically cured. Mycological cure plus “cleared” or “excellent” clinical evaluation remained for 73% at day 42 vs 5% of the placebo group (NNT=1.47).10

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