Topical Retinoids in Acne Treatment:
Contemporary treatment for acne usually includes the use of several agents simultaneously. Retinoids are often added to the therapeutic regimen.
Retinoids are chemicals that are related to vitamin A. Due to their influence on the turnover of epithelial cells (the cells in the superficial layers of the skin) they have been found useful for the treatment of acne.
One of the underlying mechanisms that contributes to the production of comedones (pimples) is the excessive production and buildup of epithelial cells within the follicles (pores) of the skin. In large part, this rapid cellular growth is triggered by androgen hormones and growth factors circulating within the bloodstream.
Retinoids reverse this enhanced cellular activity by accelerating the shedding of superficial skin cells. This helps to clear the follicles of cellular debris and promotes the expulsion of mature comedones while preventing the formation of new ones. (1)
Retinoids also exhibit a direct anti-inflammatory effect, thus addressing another of the major issues confronted by acne sufferers: The immune response to irritating fatty acids that are generated when bacteria (e.g., Propionibacterium acnes) metabolize sebum trapped within plugged follicles.
Retinoids can be used either systemically – Accutane (isotretinoin) is the name familiar to most people – or topically. Topical retinoids most commonly employed in acne treatment include tretinoin, isotretinoin, adapalene, and tazarotene; other formulations (retinaldehyde, retinol, and retinyl esters) are sometimes used in cosmetic preparations used by acne sufferers.
The major advantage to using topical, rather than systemic, retinoids is their much milder side effect profile.
Comparison of Efficacy and Tolerability among Different Retinoid Preparations
Although newer agents seem to be somewhat more effective than older ones in clinical trials, such differences may not be noticeable to persons who use these medications on a daily basis; tolerability is improved with newer products, however. Notably, recently-developed formulations tend to be more expensive.
Tretinoin, the first retinoid agent available in topical form, is still widely used. Recent advances in delivery systems (e.g., Retin-A Micro, Ortho-Neutrogena, Avita) have decreased the skin irritation that was common with earlier formulations and have improved the stability of the product when it is exposed to sunlight.
Isotretinoin, in general, is about as effective as tretinoin for reducing the severity of acne (number of inflammatory lesions and comedones), but it is usually better-tolerated than tretinoin. Isotretinoin has largely been supplanted by newer agents.
Adapalene (Differin), a newer synthetic retinoid, is at least as effective as tretinoin or isotretinoin for reducing acne severity, but it is arguably the best-tolerated topical preparation (i.e., the fewest side effects) on the market. (2)
Tazarotene (Tazorac), which is currently only licensed in the United States for acne treatment, is more effective than older agents and is possibly more effective than adapalene, but it appears to be less-well-tolerated than adapalene.
Side Effects and Precautions Associated with Topical Retinoids
Topical retinoids are generally regarded as safe when used according to recommended guidelines. However, because oral retinoids have significant side effects – not the least of which is their known teratogenicity (ability to cause serious birth defects) – the topical use of these agents in certain individuals is contraindicated.
Common side effects associated with topical retinoids include:
- increased skin sensitivity to wind and cold
- sensitivity to sunlight (increased burning)
- temporary hyper- or hypopigmentation
Precautions pertaining to the use of topical retinoids include the following:
- Prolonged exposure to topical retinoids may increase the likelihood of side effects.
- Isotretinoin and tazarotene (Tazorac) are designated Pregnancy Category X and should not be used during pregnancy or by women who are considering pregnancy.
- Tretinoin and adapalene are designated Pregnancy Category C, which means that a risk cannot be ruled out; thus, they should probably be avoided during pregnancy, especially since other options are available for treating acne during pregnancy.
- Topical retinoids should be avoided during lactation, because the effects of these agents on nursing infants are unknown.
- Safety of retinoids in children younger than 12 years has not been studied.
Topical retinoids, used alone or in combination with other agents, are effective tools for the management of acne. When used as recommended, they are also safe. (3)
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