Medicine for acne : Benzoyl peroxide

Benzoyl peroxide

The primary effect of benzoyl peroxide is antibacterial, therefore it is most effective for inflammatory acne consisting of papules, pustules, and cysts, although many patients with comedone acne respond to it. Benzoyl peroxide is less effective than vitamin A acid at disrupting the microcomedo. Benzoyl peroxide and isotretinoin significantly reduce noninflamed lesions in 4 weeks. In one study, benzoyl peroxide had a more rapid effect on inflamed lesions with significant reductions at 4 weeks, whereas the use of isotretinoin showed a significant improvement at 12 weeks.

Preparations.

Benzoyl peroxide is available over the counter and by prescription. Some examples of benzoyl peroxide preparations are water-based gel (Benzac AC 2.5%, 5%, and 10%), alcohol-based gel (Benzagel 5% and 10%), and acetone-based gel (Persa-gel 5% and 10%) (see the Formulary). Water-based gels are less irritating, but alcohol-based gels, if tolerated, might be more effective. Benzoyl peroxide is also available in a soap base in strengths from 2.5% to 10%.

Mechanism of action.

Benzoyl peroxide produces a drying effect that varies from mild desquamation to scaliness, peeling, and cracking. Patients should be reassured that drying does not cause wrinkles. It causes a significant reduction in the concentration of free fatty acids via its antibacterial effect on P. acnes. This activity is presumably caused by the release of free radical oxygen, which is capable of oxidizing bacterial proteins. Benzoyl peroxide seems to reduce the size of the sebaceous gland, but whether sebum secretion is suppressed is still unknown. Patients should be warned that benzoyl peroxide is a bleaching agent that can ruin clothing.

Principles of treatment.

Benzoyl peroxide should be applied in a thin layer to the entire affected area. Most patients experience mild erythema and scaling during the first few days of treatment, even with the lowest concentrations, but adapt in a week or two. It was previously held that vigorous peeling was necessary for maximum therapeutic effect; although many patients improved with this technique, others became worse. Recent studies show that an adequate therapeutic result can be obtained by starting with daily applications of the 2.5% or 5% gel and gradually increasing or decreasing the frequency of applications and strength until mild dryness and peeling occur.

Allergic reaction.

Approximately 2% of patients develop allergic contact dermatitis to benzoyl peroxide and must discontinue its use. The sudden appearance of diffuse erythema and vesiculation suggests contact allergy to benzoyl peroxide.