Does treatment with topical metronidazole improve seborrheic dermatitis?

Journal of Family Practice, June, 2001 by A. Christian Iudica

Parsad D, Pandhi R, Negi KS, Kumar B. Topical metronidazole in seborrheic dermatitis: a double-blind study. Dermatology 2001; 202:35-37.

* BACKGROUND Current topical treatments of seborrheic dermatitis include steroids, selenium sulfide, pyrithione zinc, coal tar preparations, terbinafine, ketoconazole, and ultraviolet phototherapy. Topical steroids are often of limited use because of disease chronicity. Randomized controlled trials with bifonazole shampoo, ketoconazole cream, and lithium succinate ointment claim clinical efficacy.[1-4] Topical metronidazole has never been evaluated in the treatment of seborrheic dermatitis.

* POPULATION STUDIED The study participants were 44 adults (mean age=24 years; range: 19-40 years) clinically diagnosed with seborrheic dermatitis in a specialty setting. The patients were to have discontinued any other topical treatments at least 2 weeks before enrollment. The study took place in India, but the clinical setting was not further detailed.

* STUDY DESIGN AND VALIDITY The patients were randomly assigned by an undisclosed method (allocation concealment uncertain) to either the treatment (n=22) or placebo group (n=22). The treatment group applied 1% metronidazole gel to affected areas twice daily. The placebo group applied only the vehicle gel in an identical container with the same frequency. Six sites were evaluated (scalp, eyebrows, bridge of the nose, nasolabial folds, posterior ears, and chest) for signs and symptoms (erythema, scales, papules, and pruritus) at 2-week intervals for 8 weeks. A numerical grade (0=clear; 1=mild; 2=moderate; 3=severe) was given for each sign or symptom at each site and then totaled for an overall severity score. Patients were questioned regarding adverse effects and concomitant medication use at each visit. A global evaluation was made at the final visit. Patients were ascertained to have complete clearing, marked improvement, moderate improvement, or slight improvement. They were analyzed in their respective randomized groups; however, persons not completing the study were not included for analysis.

* OUTCOMES MEASURED The primary outcomes measured were seborrheic dermatitis severity scores and global evaluation of clinical improvement. The clinical tolerability of treatment versus placebo was also evaluated.

* RESULTS Twenty-one patients (95%) were included for analysis in the treatment group and 17 (77%) in the placebo group. Baseline severity scores and the distribution of seborrheic dermatitis were not found to be significantly different between treatment groups. One patient in the treatment group left for reasons unrelated to the study. Five patients in the placebo group left for lack of clinical improvement or worsening disease. At 8 weeks, the mean severity score between the treatment and placebo groups was 28.5 versus 7.9 (P [is less than] .001), respectively. The difference was statistically significant as early as 2 weeks. Fourteen patients in the treatment group versus 2 patients in the placebo group were noted to have marked improvement or complete clearing at the global evaluation (P [is less than] .0001; number needed to treat=2).

RECOMMENDATIONS FOR CLINICAL PRACTICE

This small, reasonably well-done study indicates that topical metronidazole is effective in the treatment of seborrheic dermatitis. Although not adequately powered, this study also reveals no clinically significant side effects from the treatment. The high baseline severity scores and specialty setting makes me wonder if the patients had more significant or refractory disease than seen in a primary care setting, and thus would have a greater response to therapy versus placebo. Ketoconazole cream is slightly cheaper than metronidazole gel (approximately $48 vs $62 for 45 oz) and also has been shown to be efficacious with once-daily application. Head-to-head studies in a family practice setting Would be helpful. In the meantime, topical metronidazole appears to be an effective alternative in the treatment of seborrheic dermatitis.

A. Christian Iudica, MD University of Virginia Health System, Charlottesville E-mail: aci7w@virginia.edu

REFERENCES

[1.] Zienicke H, Korting HC, Braun-Falco O, et al. Comparative efficacy and safety of bifonazole 1% cream and the corresponding base preparation in the treatment of seborrhoeic dermatitis. Mycoses 1993; 36:325-31.

[2.] Segal R, David M, Ingber A, Lurie R, Sandbank M. Treatment with bifonazole shampoo for seborrhea and seborrheic dermatitis: a randomized, double-blind study. Acta Dermato-Venereologica 1992; 72:454-55.

[3.] Green CA, et al. Response of seborrheic dermatitis of the face, scalp and trunk to topical ketoconazole. Br J Dermatol 1987; 116:217-21.

[4.] Efalith Multicenter Trial Group. A double-blind, placebo-controlled, multicenter trial of lithium succinate ointment in the treatment of seborrheic dermatitis: Efalith Multicenter Trial Group. J Am Acad Dermatol 1992; 26:452-57.