Keratolytics and abrasives are effective in mild and moderate acne. They peel off superficial layers of skin and unblock pilosebaceous follicular openings. Benzoyl peroxide has an antibacterial effect. It should be used daily over a prolonged period to produce improvement. Excess dryness and irritation may occur during first two weeks, but a reduction in application frequency and use of a moisturiser may alleviate these symptoms.
The vitamin B3 derivative, nicotinamide, possesses anti-inflammatory properties. When applied topically in the form of a gel, it reduces inflammation in mild to moderate acne. It has no antibacterial activity so does not cause bacterial resistance.
Systemic antibiotics are effective in moderate to severe acne. They have antibacterial action against Propionibacterium acnes, anti-inflammatory properties, and reduce keratin in pilosebaceous ducts. Systemic antibiotics need to be given for a minimum of three months and patients should not expect much improvement in the first month. Their use is often associated with thrush and occasionally diarrhoea. Topical antibiotics are of value in mild acne. Using a topical preparation greatly reduces the risk of GI intolerance and secondary infection. The topical antibiotic azelaic acid is indicated for mild to moderate acne. Marked improvement usually occurs after one month, although five or six months may be required to resolve deep lesions. It is less irritant than benzoyl peroxide or tretinoin, but some patients may exhibit photosensitivity.
Systemic retinoid therapy with isotretinoin is extremely effective in very severe and nodulocystic acne and prevents excessive scarring. It has several mechanisms of action including a marked reduction in sebum excretion, alteration of bacterial flora in pilosebaceous follicles and peeling of the superficial layers of the skin. Isotretinoin can affect lipid metabolism and liver enzymes. Hyperostoses have also been observed after relatively high and prolonged treatment. Regular monitoring of blood parameters is necessary and effective contraceptive measures must be used by women because it is teratogenic. Topical retinoids such as adapalene are indicated for mild to moderate acne. Foetal abnormalities have not been associated with topical retinoids but it is advisable to avoid use in pregnancy.
The antiseptic chlorhexidine is used for its antibacterial activity.
Some combinations of retinoids, antibiotics and benzoyl peroxide have produced a synergistic effect.
The combination of triethyl citrate and ethyl linoleate is also synergistic. Used together, the two agents reduce sebum production, inhibit hyperkeratinisation, suppress the growth of P. acnes and control inflammation.