Oral isotretinoin is the standard treatment for severe acne and is currently the most effective treatment for acne. Isotretinoin acts on all pathophysiological aspects of acne pathogenesis, and although the therapeutic effect is significant, it is not used as the treatment of choice for mild acne as much as possible, considering its adverse effects. Indications for the use of oral isotretinoin: (1) severe nodular cystic acne and its variants; (2) inflammatory acne with scar formation; (3) moderate to severe acne that has failed to respond to the following treatments: 3 months of combination therapy, including systemic tetracycline; (4) acne with severe psychological stress (disfigurement phobia); (5) gram-negative bacillary folliculitis; (6) frequent recurrences requiring repeated and (6) Patients with frequent relapses requiring repeated and long course systemic antibiotics; (7) A small number of patients who need rapid healing for some reason. Dose: The commonly used dose is 0.25-0.5 mg/(kg.d), and the dose should not exceed 0.5 mg/(kg.d) in order to reduce adverse reactions. The duration of treatment is determined by the patient’s body weight and the daily dose used. The minimum cumulative dose is targeted at 60 mg/kg, but can be increased to 75 mg/kg if the cumulative dose reaches 60 mg/kg without satisfactory efficacy. However, even if grade 1 acne is completely cleared, the probability of permanent cure is significantly reduced if isotretinoin is discontinued before the 60 mg/kg domain value is reached. There is also so-called shock therapy, which involves the use of isotretinoin 0.5 mg/(kg.d) for the first 7 d of each month. This approach has been shown to be more effective in patients who have relapsed after having completed a full course of treatment, in patients with prolonged disease and in treatment-resistant acne. In some conditions, such as adolescents with severe acne, continuous low doses of isotretinoin can be used. In these patients, acne dissolution is poor in the initial phase, but isotretinoin 10-20 mg/d for 4-6 months can clear lesions more quickly, followed by topical retinoic acid to maintain efficacy. High-dose retinoic acid therapy is not advocated because the increase in efficacy is not significant and potentially serious toxic reactions may occur. Counseling and interpretation of the patient prior to the systematic use of retinoic acid is very important. It should be explained to the patient that retinoic acid can cause many adverse effects, especially teratogenic effects. Patients should use strict contraception for 1 month prior to treatment and until 3 months after the end of treatment. If pregnancy occurs during the course of treatment, abortion must be managed. A small number of patients develop depressive symptoms with the use of retinoic acid. Patients with a history of depression or in the family should use the drug with caution and discontinue it immediately in the event of mood swings or any depressive symptoms. Other adverse effects of isotretinoin are mainly dryness of the skin mucosa. There is a temporary exacerbation of acne in the initial phase. 5% of patients experience photosensitivity, joint and muscle pain, severe night blindness during night driving, severe hair loss, and blood triacylglycerols may be elevated. Liver function and lipid tests are performed before the start of treatment and reviewed after 1 month of treatment. If both are normal, no further blood tests are required. Long-term high dose application may cause epiphyseal deformities such as osteophytes, calcification of spinal ligaments, and osteoporosis. It should be noted that isotretinoin should not be applied simultaneously with tetracyclines or systemically with glucocorticoids, because isotretinoin and glucocorticoids may synergistically induce an increase in intracranial pressure. Vivamate can also be used as an alternative to isotretinoin, but it is slightly less well absorbed orally, has a slower onset of action, and has relatively milder adverse effects.