What Are Retinoids, and Why Are They Used to Treat Acne?
Retinoids Are Vitamin A Derivatives That Are Applied Topically and Can Help Reduce Acne
The Essential Information
Retinoids are commonly-prescribed topical medications that help unclog pores and reduce inflammation. The FDA has approved three prescription topical retinoids:
- Adapalene [0.1% is now also available over-the-counter]
Which retinoid works best is still up for debate because researchers have still not tested all three of them head-to-head, but if we had to take an educated guess based on the available data, tazarotene would come out slightly on top. However, we do know that no topical retinoid will completely clear the skin on its own. They are therefore often combined with other medications, especially benzoyl peroxide.
Skin irritation is expected for the first few weeks of use and subsides with continued use. Adapalene appears to produce the least irritation and tazarotene appears to produce the most.
From Dan: I have tried all three retinoids in the past, and in my personal, admittedly anecdotal experience, none of them worked very well. This is not to say they don't help some people however, and data says they can indeed reduce acne to some degree. As far as irritation goes, tazarotene was almost intolerable, producing massive amounts of skin irritation, whereas the other two weren't bad at all.
Topical retinoids are vitamin A derivatives that doctors can prescribe to treat mild-to-moderate acne. The Food and Drug Administration (FDA) has approved three topical retinoids for the treatment of chronic skin conditions, including acne. Those 3 are:
- Adapalene [0.1% adapalene is now available over-the-counter.]
All three interact with skin cells in slightly different ways, but ultimately they all work to reduce acne by unclogging pores and reducing inflammation.1-4 Doctors can prescribe each of the three retinoids in a variety of concentrations and vehicles (creams, gels, or lotions) that affect how the retinoid works within the skin and how well it is tolerated. Doctors can also prescribe a retinoid in combination with other acne-fighting medications, such as benzoyl peroxide.5
Retinoid Effectiveness Against Acne
Studies investigating the effectiveness of the three topical retinoids have demonstrated similar efficacies in the treatment of acne.6 Although a few studies have shown tazarotene to be slightly more efficacious than adapalene, "all topical retinoids are effective in reducing the number of comedones and inflammatory lesions by about 40% to 70%."2,6
Studies have shown that when patients apply tretinoin nightly for a period of 12 weeks, it results in an average reduction of 17 - 71% of non-inflammatory lesions, a 33 - 81% reduction of inflammatory lesions, and a 22 - 83% reduction in overall lesion counts.2
Studies have shown that when patients apply adapalene nightly for a period of 12 weeks, it results in an average reduction of 58% of non-inflammatory lesions, a 52% reduction of inflammatory lesions, and a 57% reduction in overall lesion counts.2
Studies have shown that when patients apply tazarotene nightly for a period of 12 weeks, it results in an average reduction of 45 - 55% of non-inflammatory lesions, a 39 - 42% reduction of inflammatory lesions, and a 44 - 52% reduction in total lesions.2
Comparing tretinoin, adapalene, and tazarotene
Unfortunately, scientists have not performed studies that compare the effectiveness of all three retinoids in the treatment of acne. Therefore, researchers cannot draw a conclusion regarding which retinoid, or which retinoid concentration or vehicle, is most effective. However, some studies comparing two of the three retinoids have concluded that adapalene may be slightly more efficacious than tretinoin, and tazarotene is slightly more efficacious than adapalene in the treatment of acne.2,5,6
Combining retinoids and benzoyl peroxide
Acne medications that combine benzoyl peroxide with retinoids have shown increased efficacy in the treatment of acne. Adapalene, tazarotene, and tretinoin microsphere gel can be combined or applied alongside benzoyl peroxide for improved acne reduction. However, benzoyl peroxide can inactivate tretinoin in its usual cream or gel vehicle and, thus, acne patients should only use benzoyl peroxide with tretinoin's microsphere gel formulation.2,5
Retinoid Side Effects
In addition to topical retinoids having slightly different efficacies in the treatment of acne, they also come with varying side effects.
All three retinoids are able to cause skin irritation, especially during the first two to four weeks of retinoid treatment, which disappears after two to three months of use. The most common forms of skin irritation include dryness, scaling, redness, and sensitivity to the sun. Studies comparing the tolerability of the three retinoids have found that patients tolerate adapalene the best, with tretinoin in second place, followed by tazarotene. For patients using tazarotene, the cream vehicle is best tolerated. Scientists have based these conclusions on 34 studies, each examining different concentrations and vehicles of the three retinoids. While 13 studies showed significant differences in tolerability, 21 studies did not.6,7
The FDA classifies adapalene and tretinoin as pregnancy category C drugs, which means animal studies have shown an adverse effect on the fetus, but medical professionals may still prescribe them when potential benefits outweigh potential risks. The FDA classifies tazarotene more severely, as a category X drug, which means the risks clearly outweigh the benefits and doctors should not prescribe it to women who are pregnant or who plan to become pregnant.8
Tretinoin, adapalene, and tazarotene work to treat mild to moderate acne by unclogging pores and possess anti-inflammatory properties. Some research has shown tazarotene to be slightly more effective than the other two retinoids, but to potentially cause greater side effects. Adapalene appears to be the retinoid with the fewest side effects. Regardless of which retinoid is administered, reduction in acne is normally incomplete, yet significant, resulting in 40 - 70% less acne.
- Shapiro, S. et al. Use of topical tretinoin and the development of noncutaneous adverse events: Evidence from a systematic review of the literature. J Am Acad Dermatol 65, 1194 - 1201 (2011). https://www.ncbi.nlm.nih.gov/pubmed/21550137
- Hsu, P., Litman, G. I., & Brodell, R. T. Overview of the treatment of acne vulgaris with topical retinoids. Postgrad Med 123, 153 - 61 (2011). https://www.ncbi.nlm.nih.gov/pubmed/21566426
- Sorg, O. & Saurat, J. H. Topical retinoids in skin aging: A focused update with reference to sun-induced epidermal vitamin a deficiency. Dermatology 228, 314 - 325 (2014). https://www.ncbi.nlm.nih.gov/pubmed/24821234
- Hubbard, B., Unger, J. G. & Rohrich, R. J. Reversal of skin aging with topical retinoids. Plast Reconstr Surg 133, 481e - 90e (2014). https://www.ncbi.nlm.nih.gov/pubmed/24675201
- Zaenglein, A. L. et al. Guidelines of care for the management of acne vulgaris. J Am Acad Dermatol 74, 945 - 73 (2016). https://www.ncbi.nlm.nih.gov/pubmed/26897386
- Costa, C. S. & Bagatin, E. Evidence on acne therapy. Sao Paulo Med J 18, 193 - 197 (2013). https://www.ncbi.nlm.nih.gov/pubmed/23903269
- Culp, L. et al. Tolerability of Topical Retinoids: Are There Clinically Meaningful Differences Among Topical Retinoids? J Cutan Med Surg 19, 530 - 538 (2015). https://www.ncbi.nlm.nih.gov/pubmed/26088502
- Chien, A. L. et al. Treatment of Acne in Pregnancy. J Am Board Fam Med 29, 254 - 262 (2016). https://www.ncbi.nlm.nih.gov/pubmed/26957383