Topical retinoids

Topical retinoids work by reducing the abnormal desquamation of skin cells into the follicular canal thus reducing the plugging. They work on the very earliest of acne lesions, the microcomedone, thus preventing more mature comedones from developing. They also appear to have some anti-inflammatory properties, although these are not their main mode of action. Finally, because of their impact on the follicular microclimate, they appear to enhance the efficacy of antibacterial products such as benzoyl peroxide (BPO) and topical antibiotics (Gollnick et al., 2003). Because of their action on the microcomedone, retinoids can be considered as maintenance therapy once active lesions have been cleared.

Topical retinoids describe a broad group of pharmaceutical products which are derived from vitamin A. Over the years, a number of different ‘generations’ of retinoids have been developed. Tretinoin and isotretinoin were the first generation; the drawbacks highlighted with these products being skin irritation, delayed and variable responses, photosensitivity and exacerbation of the acne after 2– 4 weeks (Naito et al., 2008). In order to get around the problems of skin irritation, a number of different strengths and formulations were developed including the microsphere which was designed to release the tretinoin slowly in a controlled manner (Gollnick et al., 2003). It should be noted that topical isotretinoin has a similar effect to tretinoin, but a very different effect from oral isotretinoin as it has no impact on sebum production.

Adapalene is a newer retinoid (known as third generation) in which the therapeutic action is similar to that of tretinoin, but in which the unwanted side effects of skin irritation and photosensitisation have been reduced. Adapalene also seems to be absorbed into the pilosebaceous duct more effectively than into the rest of the skin surface, thus increasing its efficacy (Naito et al., 2008). As yet there is no Cochrane review giving evidence-based guidance as to which retinoid is best to use; however, there has been a research study indicating that whilst efficacy was similar, adapalene had fewer unwanted side effects than tretinoin microsphere gel 0.1% (Thiboutot et al., 2003).

Topical retinoids can be used in women of child-bearing age; however, they should be advised to avoid pregnancy whilst using them. Should an individual become pregnant whilst using topical retinoids, they should stop the treatment immediately. Whilst it is unlikely for the topical product to have a systemic effect, this is a sensible precaution. How to apply a retinoid product?
Usually it is best to apply these at night before going to bed. The patient should be encouraged to wash the skin and dry it gently but completely before applying a thin layer of the product to the whole area to be treated, not just the lesions. Retinoids can be applied to any area of the body where acne is present including chest and back. The choice of the formulation of the product, whether a cream or a gel, will usually depend on personal preference. A gel is likely to dry the skin more and may be helpful if the skin surface is very greasy whereas a cream will be more moisturising and may be helpful if the skin surface has a tendency to get dry. After applying the treatment, the patient should wash their hands. The possible side effects of treatment have already been mentioned including redness, soreness and skin peeling and hypersensitivity to sunlight. If the former is a problem, the severity of the symptoms may be reduced by using a weaker formulation, if one is available, or by starting with less than a once-daily application (perhaps alternate days) and then building up to the required once a day. Patients should be advised to avoid overexposure to the sun and to not make use of sunbeds.