Benzaclin (Clindamycin Phosphate Topical Gel) - Description and Clinical Pharmacology

Topical Gel: clindamycin (1%) as clindamycin phosphate, benzoyl peroxide (5%)
For Dermatological Use Only - Not for Ophthalmic Use
*SAMPLE. NO RECONSTITUTION NECESSARY*

DESCRIPTION

BenzaClin^® Topical Gel contains clindamycin phosphate, (7(S)-chloro-7-deoxylincomycin-2-phosphate). Clindamycin phosphate is a water soluble ester of the semi-synthetic antibiotic produced by a 7(S)-chloro-substitution of the 7(R)-hydroxyl group of the parent antibiotic lincomycin.

Chemically, clindamycin phosphate is (C₁₈H₃₄ClN₂O₈PS). The structural formula for clindamycin is represented below:

Clindamycin phosphate has molecular weight of 504.97 and its chemical name is Methyl 7-chloro-6,7,8-trideoxy-6-(1-methyl-trans-4-propyl-L-2-pyrrolidinecarboxamido)-1-thio-L-threo-alpha-D-galacto-octopyranoside 2-(dihydrogen phosphate).

BenzaClin Topical Gel also contains benzoyl peroxide, for topical use.
Chemically, benzoyl peroxide is (C₁₄H₁₀O₄). It has the following structural formula:

Benzoyl peroxide has a molecular weight of 242.23.

Each gram of BenzaClin Topical Gel contains, as dispensed, 10 mg (1%) clindamycin as phosphate and 50 mg (5%) benzoyl peroxide in a base of carbomer, sodium hydroxide, dioctyl sodium sulfosuccinate, and purified water.

CLINICAL PHARMACOLOGY

An in vitro percutaneous penetration study comparing BenzaClin Topical Gel and topical 1% clindamycin gel alone, demonstrated there was no statistical difference in penetration between the two drugs. Mean systemic bioavailability of topical clindamycin in BenzaClin Topical Gel is suggested to be less than 1%.

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. It is suggested that the lipophilic nature of benzoyl peroxide acts to concentrate the compound into the lipid-rich sebaceous follicle.

Microbiology

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 activity against P. acnes was not examined in clinical trials with this product.

CLINICAL STUDIES

In two adequate and well controlled clinical studies of 758 patients, 214 used BenzaClin, 210 used benzoyl peroxide, 168 used clindamycin, and 166 used vehicle. BenzaClin applied twice daily for 10 weeks was significantly more effective than vehicle in the treatment of moderate to moderately severe facial acne vulgaris. Patients were evaluated and acne lesions counted at each clinical visit; weeks 2, 4, 6, 8 and 10. The primary efficacy measures were the lesion counts and the investigator's global assessment evaluated at week 10. Patients were instructed to wash the face with a mild soap, using only the hands. Fifteen minutes after the face was thoroughly dry, application was made to the entire face. Non-medicated make-up could be applied at one hour after the BenzaClin application. If a moisturizer was required, the patients were provided a moisturizer to be used as needed. Patients were instructed to avoid sun exposure. Percent reductions in lesion counts after treatment for 10 weeks in these two studies are shown below:

Study 1

BenzaClin	Benzoyl peroxide	Clindamycin	Vehicle
n=120	n=120	n=120	n=120
Mean percent reduction in inflammatory lesion counts
46%	32%	16%	+ 3%
Mean percent reduction in non-inflammatory lesion counts
22%	22%	9%	+1%
Mean percent reduction in total lesion counts
36%	28%	15%	0.2%

Study 2

BenzaClin	Benzoyl peroxide	Clindamycin	Vehicle
n=95	n=95	n=49	n=48
Mean percent reduction in inflammatory lesion counts
63%	53%	45%	42%
Mean percent reduction in non-inflammatory lesion counts
54%	50%	39%	36%
Mean percent reduction in total lesion counts
58%	52%	42%	39%

The BenzaClin group showed greater overall improvement than the benzoyl peroxide, clindamycin and vehicle groups as rated by the investigator.