Antibiotics have an effect on the bacteria Propionibacterium acne, the bacteria linked, in part, with the inflammation of acne. Theoretically, if the bacteria are reduced in numbers then less inflammation can take place and less acne occurs.

The antibiotics that are used as topical treatments in mild to moderate acne listed alphabetically are:

• Topical clindamycin

• Topical erythromycin

• Topical tetracycline

How effective are these topical antibiotics?
Treatment of acne with a combination of topical antibiotic and zinc has been shown to be more effective than with topical antibiotic alone [1] and equally effective as treatment with oral antibiotics [2]. Topical antibiotics may also be combined with benzoyl peroxide to improve efficacy [3, 4].

It is crucial to use the topical treatments correctly, in particular the prescribed number of times per day. Benefit will not be immediate and will develop over a number of weeks.

Can the bacteria become resistant?
The emergence of strains of Propionibacterium acnes and Staphylococcus epidermidis that are resistant to antibiotics is an increasing problem. In one study, 25% of acne patients were found to have erythromycin resistant strains regardless of previous exposure to erythromycin [5].

This resistance is significant as carriers of erythromycin resistant propionibacterium do not respond to oral erythromycin[6] There is also cross resistance between clindamycin and erythromycin emerging[7]

However, there is some evidence that erythromycin resistance may be overcome or prevented by using benzoyl peroxide, or zinc acetate in the same treatment, or by increasing the concentration of the erythromycin to 4%. Zinc acetate has anti- bacterial activity itself [8].

It is preferable to prescribe non- antibiotic antimicrobials (such as benzoyl peroxide) or a combination of a topical antibiotic with a non- antibiotic antimicrobial, rather than a single antibiotic preparation on its own.

Side effects of topical antibiotics
The main side effect would be irritation of the skin which can be overcome by using the treatments less frequently.

 

Topical benzoyl peroxide

Benzoyl peroxide (2.5 – 10%) has both keratolytic and antibacterial properties. It is available in a range of creams, lotions and gels and is found in several “over the counter” cleansing lotions.
 

Benzoyl peroxide reduces the number of Propionibacterium acnes and Staphylococcus epidermidis types of bacteria. It can be very effective in the treatment of mild acne.

Bacterial resistance is much less likely to emerge with benzoyl peroxide than with topical antibiotics. Combination preparations with other antimicrobial agents such as erythromycin also exist, though these are prescription only.

Benzoyl peroxide’s keratolytic action reduces the blockage of the duct of the sebaceous gland.

How long can this be used for?
This may be used for as long as it is effective, which may be months or even years.

 

Topical retinoids and azaleic acid
Topical retinoids such as tretinoin or isotretinoin are particularly effective in non- inflamed comedonal acne. There may be some initial erythema and irritation, which tends to be a problem particularly in fair- skinned individuals but this often, resolves with continued use.

Photosensitivity sensitivity of the skin to sunlight, resulting in a dermatitis can also occur. The retinoids should be applied at night and wash it off in the morning.

Adapalene

Adapalene 0.1% is a retinoid- like compound which is indicated for use in mild to moderate acne and has both comedolytic (breaks down blackheads) and anti- inflammatory properties.

Azelaic acid

Azelaic acid 20% has a similar role but may also be effective for superficial inflamed lesions and can reduce post- inflammatory hyperpigmentation, a significant problem associated with acne particularly in Asian and Afro- Caribbean skin.

 

Antibiotic treatments for acne, taken by mouth

 

Antibiotics may be given by mouth to treat acne that is moderate or severe. The antibiotics will need to be taken for up to 4 months to obtain full benefit. Though there are possible side effects, they are outweighed by the benefits of treating acne.
Tetracyclines/oxytetracycline and erythromycin are usually the first- line antibacterials prescribed. Second- generation tetracyclines, such as lymecycline, doxycycline, and minocycline, are also used.

Tetracyclines such as oxytetracycline and tetracycline are more effective than erythromycin but are unsuitable for pregnant women and women who may become pregnant during therapy.

Tetracycline and oxytetracycline absorption is reduced by drinking milk and therefore must be taken 30 minutes before meals. They are taken 2 to 4 times a day but are much less expensive than once- daily preparations.

Doxycycline and lymecycline absorption is not affected by milk and all are available as once- daily preparations, which is possibly easier to take with patients less likely to forget to take them.

Unwanted side- effects of antibiotics include the following:
 

• Stomach upset feeling sick and having diarrhoea

 

• Photosensitivity, reacting to sunlight is rare though can occur.

 

• Vaginal candidiasis or thrush is common in females.

 

• Benign intracranial hypertension - headaches of varying severity

 

• Cutaneous pigmentation - discolouration of the skin (especially with minocycline) which can be slate grey in appearance is reversible.

Though very rare, this pigmentation is more permanent when it affects the whites of the eyes.


Antibiotics and women on the pill:

Women taking the combined oral contraceptive pill have a small risk of the contraceptive being less effective with oral antibiotics although the risk reduces with longer- term antibiotic therapy. It is recommended that on commencing long- term antibiotic therapy, an additional barrier method of contraception is used for the first 21 days.

When should any effect be noted?

Antibiotics have a gradual effect with benefit noted after about 4 months duration of treatment. This should be noted and a rule of thumb is that there should be about a 20% benefit at 2 months and a 40% benefit at 4 months.

How long can antibiotics be used for?

Antibiotics can be used for as long as they are effective which may be up to a year or longer in certain circumstances. There are no particular problems with taking these for long periods of time apart from resistance of the bacteria developing.

What happens if antibiotics lose their effect?

Bacteria can develop resistance to the antibiotics in which case the acne can become worse over a period of time. If this happens then the antibiotics can be changed or treatment with isotretinoin or roaccutane may be needed.

 

Hormonal treatment for acne - an option in womenWomen with moderate acne can take cyproterone acetate orally which, has anti- androgen activity and reduces sebum production.
The combination tablet, cyproterone 2 milligrams and ethinyloestradiol 35 micrograms, is usually prescribed and this can also be use as an oral contraceptive. Its trade name is known as dianette.

It should be continued for several months for maximum benefit. This may help acne though does not always cure the acne. The theory is that it reduces the production of sebum.

​

References
[1] Habbema L, Koopmans B, Menke HE et al. A 4 per cent erythromycin and zinc combination (Zineryt) versus 2% erythromycin (ErydermR) in acne vulgaris: a randomised, double blind comparative study. Br J Dermatol 1989; 121: 497- 502

[2] Stainforth J, MacDonald- Hull S, Papworth- Smith JW et al. A single- blind comparison of topical erythromycin/zinc lotion and oral minocycline in the treatment of acne vulgaris. J Dermatol Treatment 1993; 4: 119- 22

[3]Ellis CN, Leyden J, Katz HI, Goldfarb MT, Hickman J, Jones TM, Tschen E. Therapeutic studies with a new combination benzoyl peroxide/clindamycin topical gel in acne vulgaris. Cutis. 2001 Feb;67(2 Suppl):13- 20. Erratum in: Cutis 2001 Mar;67(3):257

[4] Burkhart CN, Specht K, Neckers D. Synergistic activity of benzoyl peroxide and erythromycin. Skin Pharmacol Appl Skin Physiol. 2000 Sep- Oct;13(5):292- 6

[5] Eady EA, Jones CE, Tipper JL. Antibiotic resistant propionibacteria in acne patients: need for policies to modify antibiotic usage. Br Med J 1993; 306: 555- 6

[6] Eady EA, Cove JH, Holland KT. Erythromycin resistant propionibacteria in antibiotic treated acne patients; association with therapeutic failure. Br J Dermatol 1989; 121: 51- 7

[7] Crawford WW, Crawford IP, Stoughton RB, Cornell RC. Laboratory induction and clinical occurrence of combined clindamycin and erythromycin resistance in Corynebacterium acnes. J Invest Dermatol 1979; 72: 187- 90

[8] Fluhr JW, Bosch B, Gloor M, Hoffler U. In- vitro and in- vivo efficacy of zinc acetate against propionibacteria alone and in combination with erythromycin. Zentralbl Bakteriol. 1999 Oct;289(4):445- 56