tretinoin + isotretinoin

**Tretinoin + isotretinoin** is a combination of two retinoids, both derivatives of vitamin A, used individually to treat acne and certain skin conditions. Tretinoin (all-trans-retinoic acid) is typically used as a topical agent to promote skin cell turnover, treat acne, and reduce signs of photoaging; isotretinoin (13-cis-retinoic acid) is primarily an oral drug for severe, recalcitrant nodular or cystic acne that has not responded to other therapies. Both work by modulating gene expression, reducing sebum production, normalizing follicular keratinization, and exhibiting anti-inflammatory effects. While both are effective for various forms of acne, the combination is rarely used in clinical practice due to increased risk of additive toxicity, particularly hypervitaminosis A, and is generally not recommended unless under exceptional and closely monitored circumstances[3][4][8]. Limited studies have explored their combined use at low doses for difficult acne cases[5].