Isotretinoin is an oral retinoid for severe, scarring, or treatment resistant acne that reduces sebaceous gland size and sebum, normalizes follicular keratinization, and lowers Cutibacterium acnes density, leading to long term remission in many patients. It requires strict pregnancy prevention due to powerful teratogenicity and regulated risk management enrollment in many countries. Monitoring typically includes lipids, liver function, and mood, alongside counseling on sun protection and dryness care during therapy. Typical courses last several months with cumulative‑dose targets, and relapse may be managed with maintenance or retreatment as guided by dermatology.