Pharmacology Update

Clindamycin 1% and Benzoyl Peroxide 5% Topical Gel (DUAC)

By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD

The FDA has approved a new topical gel for the treatment of acne. The DUAC gel combines 2 time-tested ingredients, clindamycin and benzoyl peroxide. The once-daily product will be marketed by Stiefel Laboratories.

Indications

Clindamycin/benzoyl peroxide gel is indicated for the topical treatment of inflammatory acne vulgaris.1

Dosage

The gel should be applied once daily in the evening.   The skin should be gently washed, rinsed with warm water, and patted dry before application.1 The product should be stored in a cool place; refrigeration is preferred. DUAC will be supplied as a 45 g tube.

Potential Advantages

Clindamycin/benzoyl peroxide gel formations are generally more effective in reducing inflammatory lesions (papules and pustules) than clindamycin or benzoyl peroxide alone in patients with moderate to moderately severe facial acne vulgaris.1-4

Clindamycin/benzoyl peroxide gel has been shown to produce 91% inhibition (> 1 log10/cm2 from baseline) of Propionibacterium acnes 24 hours after application compared to 31% for clindamycin solution 1%.5 This organism is one of the primary factors in the pathogenesis of acne vulgaris. The side effects of clindamycin/benzoyl peroxide gel are similar to that of either ingredient alone.2

Potential Disadvantages

Clindamycin/benzoyl peroxide gel does not appear to be any more effective than benzoyl peroxide alone in treating noninflammatory (comedones) acne lesions.1,2 Benzoyl peroxide can reduce the stability of clindamycin, therefore, the formulation should be stored in a cool place and refrigeration is preferred.3 Benzoyl peroxide may promote tumor growth and the effect of the combination is not known. The manufacturer is required by the FDA to conduct postmarketing studies on UV-induced skin cancer and dermal carcinogenicity.6 Clindamycin/benzoyl peroxide carries the same warning  for pseudomembrane colitis risk due to potential systemic absorption of clindamycin.

Comments

Combining benzoyl peroxide and clindamycin has been shown to improve effectiveness of treating acne, and may also decrease the emergence of resistant strains of P acnes.7 In general, the combination was more effective than the individual ingredients in reducing inflammatory lesions.

DUAC has been shown to be more effective than benzoyl peroxide, clindamyin, or vehicle in 3 of 5 studies involving a total of 1319 subjects.1 Effectiveness was based on mean percent reduction of inflammatory lesion counts and investigator’s global assessment in 11-week studies. Mean reduction for DUAC ranged from 42-65%, benzoyl peroxide from 36-57%, clindamycin from 30-49%, and vehicle from 0-29%. Global assessment values were not reported by the manufacturer. Data from other clindamycin/benzoyl gel studies suggest a similar trend in relative effectiveness as assessed by physician and patients. In one study (n = 480), a higher percent of patients rated themselves as having moderate or excellent improvement at 10 weeks for the combination, 54% compared to 35% for benzoyl peroxide, 37% for clindamycin, and 18% for vehicle.4 The corresponding physician assessment was 64%, 37%, 26%, and 9%, respectively.

In another 10-week study (n = 287), physicians and patients rated the combination better than clindamycin and vehicle but similar to benzoyl peroxide.2 The wholesale cost for DUAC topical gel is $79.00 for a 45-g tube.

Clinical Implications

Benzoyl peroxide/clindamycin gel provides another topical option for the treatment of acne vulgaris. The individual ingredients have been used successfully for decades. The combination is more effective than clindamycin alone and modestly better than benzoyl peroxide alone but may reduce the emergence of resistant strains of P acnes

Dr. Elliott is Chair, Formulary Committee, Northern California Kaiser Permanente; Assistant Clinical Professor of Medicine, University of California-San Francisco. Dr. Chan is Pharmacy Quality and Outcomes Manager, Kaiser Permanente, Oakland, CA. Both are Associate Editors of Internal Medicine Alert.

References

1. DUAC product information. Steifel Laboratories. August 2002.

2. Tschen EH, et al. Cutis. 2001;67(2):165-169.

3. Lookingbill DP, et al. J Am Acad Dermatol. 1997; 37(4):590-595.

4. Leyden JJ, et al. Am J Clin Dermatol. 2001;2(1):33-39.

5. Leyden JJ. Cutis. 2002;69(6):475-480.

6. FDA Approval letter. August 2002 (http://www.fda.gov).

7. Cunliffe W, et al. Br J Dermatol. 2000;143 (suppl 57):72-73.