As skin-care ingredients go, adapalene (like the popular over-the-counter option Differin) and its prescription cousin tretinoin have a lot in common. Both are retinoids—vitamin A derivatives ...

However, according to Dr. Ariel Ostad, a cosmetic surgeon based in New York City, products that use a prescription-strength retinoid called adapalene are outliers in this pricey OTC mark-up.

Adapalene 0.1%; alcohol-free. Biochemical and pharmacological profile studies have demonstrated that adapalene is a modulator of cellular differentiation, keratinization, and inflammatory ...