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
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.
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.
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.