Retinoids are classified into different generations based on their structure and pharmacological activity. The first-generation includes tretinoin and isotretinoin, which are structurally similar to retinoic acid. Second-generation retinoids, like etretinate and acitretin, have a modified structure that reduces side effects. Third-generation retinoids, such as adapalene and tazarotene, are designed to target specific receptors, minimizing systemic toxicity.
