Adapalene Gel: New Synthetic Retinoid
By William T. Elliott, MD, and James Chan, PharmD, PhD
A new synthetic retinoid has been approved by the FDA for the treatment of acne. Adapalene (Differin, Galderma) is a naphthoic acid derivative that has retinoid-like properties. It is similar in its anti-inflammatory and comedolytic properties to topical tretinoin but may be somewhat less irritating and drying.
Adapalene is indicated for the topical treatment of acne vulgaris.
Adapalene has been shown to reduce the number and severity of acne lesions after 12 weeks of therapy. A comparative study (n = 228) suggested that adapalene was more effective than tretinoin gel 0.025% in the treatment of acne vulgaris.1 Statistically significant differences in the reduction in total and noninflammatory lesions were reported at 12 weeks for adapalene compared to tretinoin. The reductions in inflammatory lesions were not statistically significant, although the trend favored adapalene. Reductions in lesions did not reach statistical significance until week 12. Significantly less scaling was reported for those randomized to adapalene.
Like tretinoin, local irritation is the most common side effect of adapalene. Erythema, dryness, scaling, burning, or pruritus occurs in 10-40% of patients, especially during the first 2-4 weeks of treatment. Burning or itching immediately after application also occurs in 20% of patients.
As with tretinoins, patients should be advised to avoid or minimize exposure to excessive natural and artificial UV irradiation.
Adapalene is supplied as a white, odorless gel in 0.1% strength (15 g, 45 g). It is applied at bedtime, once a day.
Adapalene is a retinoid-like compound that binds to nuclear receptors but not to cytosolic receptors.2,3 It may act by normalizing the differentiation of follicular epithelial cells, resulting in decreased microcomedone formation. Comparative studies indicate that adapalene is as effective as tretinoin 0.025% gel and may be marginally better tolerated, although the number of patients discontinuing the trial were similar.