Acne Treatment with Topical Antibiotics
Pathogenesis of inflammation
P. acnes is found in low numbers on normal skin and is probably not infectious. The bacteria may be the primary factor in the production of inflammatory acne. The mixture of abnormally desquamated cells and excessive amounts of sebum in the microcomedo provides a lipid rich environment for bacteria to thrive. They produce neutrophil chemotactic factors and stimulate neutrophils to release lysosomal enzymes. These proinflammatory mediators attack the microcomedo follicular wall and contribute to the formation of inflammatory lesions. Acne improves when the P. acnes numbers are reduced. P. acnes is sensitive to many antibiotics. The problem is to deliver antibiotics into the lipid-rich environment of the sebaceous follicles where the organism is proliferating. Topical and oral antibiotics are used alone or in combination with topical retinoids. Retinoids disrupt the microcomedo.
Benzoyl peroxide is an effective non-specific antimicrobial agent. It penetrates sebum and suppresses the growth of P. acnes more effectively than topical clindamycin and erythromycin. It has only a weak effect on inflammation and little comedolytic activity. It does not stimulate bacterial resistance like erythromycin and clindamycin. Product formulations include gels, creams, lotions, cleansers and bar soaps. It is available in available in 2.5, 4, 5, 6, 8, 9 and 10 percent formulations. Sulfoxyl strong and Sulfoxyl regular are 10 and 5 percent formulations of benzoyl peroxide that contain sulfur. They are antibacterial and keratolytic and can be very effective for patients with pustular acne and oily skin.
PB causes concentration-dependent irritation, erythema and dryness. It has the potential to cause allergic contact dermatitis. Suspect this side effect when patients complain of the acute onset of erythema and itching at a higher intensity that would be expected from just irritation from the base. Benzoyl peroxide can bleach clothing.
Benzoyl peroxide is available as a 5 percent gel in combination with erythromycin called Benzamycin. There are two benzoyl peroxide clindamycin combination products. Benzaclin is available in a jar.
Duac is available in a tube. These combination products result in greater reductions in inflammatory lesions and comedones at 16 weeks when compared to monotherapy with clindamycin. BP helps to reduce the emergence to resistant variants of P. acnes.
Clindamycin is effective as monotheryapy for short periods of treatment. Products include solution, lotions, gels and pledgets. It can be especially effective when used as combination therapy with retinoids such as tretinoin, tazarotene, and adapalene. If use for longer than 3 months is required than switch to a combination benzoyl peroxide/clindamycin product to avoid the problems of bacterial resistance to clindamycin.
Sodium sulfacetamide and sulfur
These combination products have been available for many years. They have antimicrobial activity and are keratolytic. They inhibit comedogenesis by normalizing desquamation of the follicular epithelium. They may cause irritation. Recently may gel, cream and cleanser formulations have become available. Klaron lotion is pure sulfacetamide and is less irritating.
Topical Azelaic acid has been available in Europe for years. It reduce P. acnes to about the same degree as topical clindamycin. It has mild comedolytic and antiinflammatory activity. It also suppresses post-inflammatory hyperpigmentation that is a problem in patients with a dark complexion.