Patients suffering from mild to moderate forms of acne, either comedonal or papulopustular are usually recommended topical treatments that involve applying topical retinoids or topical antibiotics or a combination of both depending on the severity and nature of the acne lesions. The topical agents have a direct or indirect influence on the pathogenic factors which are responsible for acne formation.

Topical Antibiotics

Topical antibiotic treatment agents were extensively used before the 1990s, but this led to the development of bacterial resistance to the antibiotics. Therefore, nowadays dermatologists are of the opinion that these are to be used in combination with topical retinoids or benzoyl peroxide or azelaic acid for greater efficacy as well as to curb bacterial resistance.

Topical antibiotics in conjunction with other antimicrobial agents are best for treating mild inflammatory acne characterized by the presence few papules, pustules as well as few comedones. Twice a day application of this combination produces desired results.

Commonly used topical antibiotics are clindamycin and erythromycin. There are other antibiotics, which can be applied topically, but these are less in use due to lower efficacy and a greater chance of adverse effects.

The Function of Topical Antibiotics

Topical antibiotics like erythromycin and clindamycin work by reducing the population of Propiobacterium acnes (P. acnes) in the hair follicles, particularly on the epidermal surface. This leads to lessening of the skin surface lipids which is produced by the P. acnes lipase activity. Topical antibiotics have a mild anti inflammatory effect as they curb inflammatory cell chemotaxis. Clindamycin has the ability to indirectly reduce the formation of comedones as well. The benefit of topical antibiotic usage is that they do not cause extreme levels of skin irritation as compared to some topical retinoids. Thus, the main mechanism of action of topical antibiotics is the inhibition of inflammation caused by bacteria rather than a direct anti acne effect.

The Disadvantages Associated with Topical Antibiotics

The major drawback of topical antibiotic usage, which has been proven over the last two decades, is that its extensive use has resulted in the emergence and increase in bacterial resistance. Thus, topical antibiotics should not be used as a monotherapy over the long term. If monotherapy is necessary then it is to be used for a short period lasting only for 3-4 weeks. Once P. acnes become resistant to antibiotics they can pose significant problems for the affected individual. Therefore it is recommended that topical antibiotics be used in combination with anti microbials because this will help suppress the existing P. acnes resistant strains as well as negate the formation of newer varieties of resistant P. acnes colonies. It also hinders colonization with antibiotic resistant Staphycoccus aureus. Adverse effects include erythema, peeling, dryness and burning and also relativly low onset of action is observed when topical antibiotics are used as a monotherapy. Treatment should be stopped at once when inflammatory lesions are reduced.

Clindamycin

This is a semi synthetic antibiotic and has a long history of success since the 1970’s for the treatment of acne vulgaris. It is mostly safe and well tolerated. Clindamycin has an effect on Propionibacterium acne, which is reduced in number with topical use so that less inflammation takes place and thus less acne occurs. There are two topical Clindamycin products namely Dalacin T and Zindalcin. Topical Clindamycin is available as a solution, ointment, gel or pledgetes. There is also a liquid form available with zinc acetate, which helps reduce P.acne counts and helps decrease free fatty acids and surface lipids.

Erythromycin

This is also an established and effective topical antibiotic in the treatment of mild to moderate papulo pustular acne. It reduces the P. acne counts considerably and lessens the Micrococcaceae from the sebaceous gland ducts. Though there are some varieties of P. acnes still emerging which are somewhat resistant to erythromycin, in recent years they have been counteracted by using four percent of erythromycin formulation as against two percent used in earlier forms. Also, adding zinc acetate to the erythromycin formulation has led to enhancement of the treatment’s bactericidal effect as well as sebum suppression.

Topical Antibiotics Combined with Other Anti-bacterials

In order to maximize bactericidal effect as well as negate the effects of bacterial resistance, fixed combinations of topical antibiotics with benzoyl peroxide, retinoids and zinc are used. The overall effect on acne lesions is also brought about by better absorption of the drugs as well as improved patient cooperation. The standard available fixed combinations include erythromycin 3% with benzoyl peroxide 5%, erythromycin 4% with tretinoin 0.02% gel, erythromycin 2% with isotretinoin 0.5% gel, erythromycin 1.2% with zinc acetate 0.377% solution, clindamycin 1% and benzoyl peroxide 0.5% gel, and clindamycin 1% with tretinoin .02% gel.

An erythromycin 4% and zinc combination reduced inflammatory lesions by 85% versus 46% reduction using 2% erythromycin alone. Three clinical studies involving 1259 patients concluded that the combination of clindamycin 1% with benzoyl peroxide 5% was more effective than either drug used alone in reducing lesions and suppressing P. acnes. Adapalene gel 1% plus clindamycin 1% brought about significant reduction in inflammatory as well as non-inflammatory lesions over a period of 12 weeks.