Antibiotics in Acne

Mechanism

• They reduce the number of bacteria on the skin surface and in the follicles, including Propionibacterium acnes
• They have an anti-inflammatory action

Topical Antibiotic

• Clindamycin
• Erythromycin

Concerns with Topical AB

• Dryness of the treated area is usually mild but is a common side effect of topical antibiotics. If the skin is visibly scaly, apply a light non-oily moisturiser.
• Skin irritation from topical antibiotics is rarely severe. Occasionally, irritation means that the patient should stop using the product. Lotions are less likely to cause irritation than solutions or gels.
• Contact dermatitis (red, dry, itchy skin) can be due to irritancy or allergy. It can be treated with a topical corticosteroid such as hydrocortisone cream (available at a NZ pharmacy without prescription).
• Bacterial resistance to antibiotics most frequently arises with intermittent use of topical antibiotics. 
• To reduce the chance of bacterial resistance, apply topical antibiotics liberally twice daily and also use benzoyl peroxide and/or a topical retinoid.

Oral Antibiotics

• Limit courses to 3–6 months to minimise antibiotic resistance and adverse effects.
• After acne has cleared, maintenance therapy for 3–12 months or longer with a topical retinoid is a good option to prevent recurrence
• Tetracycline
• doxycycline [50–100 mg daily], limecycline, minocycline
• These are not suitable for children younger than 10 years old because they may stain teeth yellow
• Erythromycin 
• erythromycin 250–500 mg orally, twice daily is an alternative
• Trimethroprim
• Cotrimoxazole

Concerns with Oral AB

• Allergy – oral antibiotics can cause a variety of rashes in those susceptible. These can be mild or life-threateningly severe. Allergy to a tetracycline or to erythromycin is very uncommon, but more than 2% of those on trimethoprim or cotrimoxazole become allergic to it.
• Photosensitivity may be a problem for those taking doxycycline. Taking the medicine after the evening meal reduces the risk of sunburn. Dress up and protect your skin from exposure to the sun.
• Gastrointestinal disturbance affects about 5% of patients and includes nausea, colicky pain and diarrhoea.
• Thrush (Candida albicans infection) affects 5% of treated women and most often affects the vagina. Thrush can also affect the oral mucosa or body folds (intertrigo), particularly in diabetics or in obesity. Thrush is less likely with erythromycin than with tetracycline.
• Bacterial resistance may occur but is less common with the use of oral antibiotics than with topical antibiotics.
• Acne antibiotics are unlikely to result in failure of the oral contraceptive pill but if you are concerned, add a barrier method and talk to your doctor about your risks

Considerations

• Acne is an inflammatory disease and is not an infection
• Antibiotics  are often prescribed for months or years, because acne is a chronic skin condition
• Topical antibiotics are more likely to induce bacterial resistance than oral antibiotics.
• P. acnes bacterial resistance is common in people treated with antibiotics for acne
• Resistance genes can spread from P. acnes to other types of bacteria such as Staphylococcus epidermidis and S. aureus
• Topical antibiotics alone are no more effective in acne than topical retinoids or benzoyl peroxide.
• Topical or systemic antibiotics should always be used in combination with benzoyl peroxide, a topical retinoid or azelaic acid. In women, they may also be used in combination with antiandrogen therapy or oral contraceptive pill.
• There have been no reports of bacterial resistance being caused by benzoyl peroxide. Benzoyl peroxide has been shown to reduce the prevalence of resistant strains of P. acnes.
• Topical antibiotics should not be used at the same time as oral antibiotics.
• The optimum dose and duration of treatment with oral antibiotics that can be given without inducing bacterial resistance is unknown
• However, low-dose doxycycline (50 mg daily) is probably less likely to induce resistance than standard-dose doxycycline (100–200 mg daily) and may be as effective in controlling the acne.
• Oral antibiotics are known to act by reducing bacterial colonisation and inflammation in the affected follicles, but they do not cure acne.
• There is no benefit to switching antibiotics to improve efficacy in acne treatment. Switching may increase the risk of bacterial resistance

References:

1. Antibiotics for acne. April 2014. http://www.dermnetnz.org/acne/acne-antibiotics.html
2. http://www.nps.org.au/publications/health-professional/health-news-evidence/2013/oral-antibiotics-for-acne
3. http://emedicine.medscape.com/article/1069804-medication#6
4. http://www.australianprescriber.com/magazine/35/6/180/2