Duac Topical Gel

CLINICAL PHARMACOLOGY

Mechanism Of Action

Clindamycin

Clindamycin is a lincosamide antibacterial [see Microbiology]

Benzoyl Peroxide

Benzoyl peroxide is an oxidizing agent with bacteriocidal and keratolytic effects, but the precise mechanism of action is unknown.

Pharmacokinetics

A comparative trial of the pharmacokinetics of DUAC Gel and 1% clindamycin solution alone in 78 subjects indicated that mean plasma clindamycin levels during the 4-week dosing period were < 0.5 ng/mL for both treatment groups.

Benzoyl peroxide has been shown to be absorbed by the skin where it is converted to benzoic acid. Less than 2% of the dose enters systemic circulation as benzoic acid.

Microbiology

Clindamycin binds to the 50S ribosomal subunits of susceptible bacteria and prevents elongation of peptide chains by interfering with peptidyl transfer, thereby suppressing protein synthesis.

In Vivo Activity

No microbiology studies were conducted in the clinical trials with this product.

In Vitro Activity

The clindamycin and benzoyl peroxide components individually have been shown to have in vitro activity against Propionibacterium acnes, an organism which has been associated with acne vulgaris; however, the clinical significance of this in vitro activity is not known.

Drug Resistance

There are reports of an increase of P. acnes resistance to clindamycin in the treatment of acne. In patients with P. acnes resistant to clindamycin, the clindamycin component may provide no additional benefit beyond benzoyl peroxide alone.

Clinical Studies

In five randomized, double-blind clinical trials of 1,319 subjects, 397 used DUAC Gel, 396 used benzoyl peroxide, 349 used clindamycin, and 177 used vehicle. Subjects were instructed to wash the face, wait 10 to 20 minutes, and then apply medication to the entire face, once daily in the evening before retiring. DUAC Gel applied once daily for 11 weeks was significantly more effective than vehicle, benzoyl peroxide, and clindamycin in the treatment of inflammatory lesions of moderate to moderately severe facial acne vulgaris in three of the five trials (Trials 1, 2, and 5).

Subjects were evaluated and acne lesions counted at each clinical visit at Weeks 2, 5, 8, 11. The primary efficacy measures were the lesion counts and the investigator's global assessment evaluated at Week 11. Percent reductions in inflammatory lesion counts after treatment for 11 weeks in these 5 trials are shown in Table 2.

Table 2: Mean Percent Reduction in Inflammatory Lesion Counts

Treatment Trial 1
(n = 120)
Trial 2
(n = 273)
Trial 3
(n = 280)
Trial 4
(n = 288)
Trial 5
(n = 358)
DUAC Gel 65% 56% 42% 57% 52%
Benzoyl Peroxide 36% 37% 32% 57% 41%
Clindamycin 34% 30% 38% 49% 33%
Vehicle 19% -0.40% 29% 29%

The group treated with DUAC Gel showed greater overall improvement in the investigator's global assessment than the benzoyl peroxide, clindamycin, and vehicle groups in three of the five trials (Trials 1, 2, and 5).

Clinical trials have not adequately demonstrated the effectiveness of DUAC Gel versus benzoyl peroxide alone in the treatment of non-inflammatory lesions of acne.

Last reviewed on RxList: 1/21/2014
This monograph has been modified to include the generic and brand name in many instances.

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