The etiology and pathogenesis of inflammatory bowel disease (IBD) are still not well understood, and clinically IBD includes ulcerative colitis (UC) and Crohn’s disease (CD). (1) 5-ASA5-ASA is currently the main drug of choice for inducing and maintaining remission in mild to moderate UC and mild CD, especially in maintaining remission, but the efficacy in moderately active CD is unclear. 5-ASA includes the traditional salazosulfapyridine (SASP) and different types of 5-ASA preparations . Because of the adverse effects of SASP such as leukopenia, myelosuppression, and rash, which can be as high as 5% to 30%, 5-ASA is currently recommended. there are no significant differences in the efficacy of the different 5-ASA formulations. Different preparations and dosage forms of 5-ASA have different sites of action: pH-dependent release type acts on the terminal small intestine and colon; time-controlled release type acts on the whole small intestine and colon; the range of action of the suppository is about 10 cm, the foam form can reach 15 cm to 20 cm, and the enema solution can reach the splenic flexure of the colon. Clinically, suitable preparations and dosage forms should be selected according to the extent of lesions. For patients with lesions confined to the rectum or rectosigmoid colon, the importance of local medication needs to be noted, and the combination of oral and local medication is more effective. The combination of oral and topical agents may also improve the efficacy in those with extensive lesions. For mildly active CD, mesalazine can be used for both the terminal ileal and ileocolic types. Patients with IBD should receive maintenance therapy, except for patients with mild initial recurrences in the distal colon, few recurrences, or mild recurrences that are easily controlled. the recommended duration of 5-ASA maintenance therapy is generally 3 to 5 years or longer. However, the efficacy of 5-ASA maintenance therapy for this group of patients with hormone-induced remission is currently uncertain. The maintenance dose recommended by our IBD diagnosis and treatment guidelines is the full or half of the induced remission dose. (2) Glucocorticoids The indications for glucocorticoids in UC are: active UC is still not effectively controlled after 2 to 4 weeks of 5-ASA treatment in adequate doses; mild active CD confined to the terminal ileum, ileocecal region or ascending colon, a locally acting hormone, budesonide, can be used; moderate to severe active For moderately active CD, glucocorticoids are preferred. For moderately active patients with lesions confined to the ileocecal region, budesonide can be considered to reduce the adverse effects of systemic hormones. However, it should be noted that the efficacy of budesonide is not as good as that of systemic glucocorticosteroids. Regarding the duration of glucocorticosteroid application, it is currently accepted that the duration of UC is short and the duration of CD is relatively long, and the dosage is generally tapered after 8 to 12 weeks of medication for symptom control. It should be noted that glucocorticosteroids should not be used as maintenance medication and should be tapered slowly after induction of remission; rapid taper may lead to early relapse of IBD. It is recommended to reduce 5mg to 10mg per week until 20mg/d, then taper at a rate of 2.5mg per week. During the course of glucocorticoid therapy, close attention should be paid to the timing and judgment of the need to switch treatment and the selection of an appropriate switch treatment plan. (3) Immunosuppressant thiopurines: Currently, azathioprine (AZA) and 6-mereaptopurine (6-MP) are mainly used to induce remission of active IBD that is ineffective or dependent on hormones, but their onset of action is slow. AZA is the most commonly used drug to maintain remission in CD and is effective in maintaining clinical remission after hormone withdrawal or reducing the amount of hormone. (American GastroenterologicalAssociation (AGA) published the Clinical Guidelines for Induction and Maintenance of Remission with Azathioprine, Methotrexate, and Antitumor Necrosis Factor Biologics for Crohn’s Disease, which clearly states that, with regard to AZA monotherapy, it is not recommended for induction of remission in active moderate-to-severe CD, but Strong Grade recommends its use for the treatment of CD in maintenance remission. If adverse reactions occur after AzA use, it can be replaced with 6-MP. methotrexate (MTX) can be replaced when thiopurines are ineffective or not tolerated. The target dose of AZA recommended in Europe and the United States is 1.5 mg/kg/d to 2.5 mg/kg/d. For Chinese, the generally recommended dose is 50 mg/d, on which there is no consensus. The incidence of myelosuppression is significantly higher when aminosalicylic acid is combined with AZA, so close monitoring is required. CsA is recommended as the first-line treatment for refractory severe UC because of its rapid onset of action by the intravenous route and short-term efficiency of 60% to 80%. showed that cyclosporine at 2 mg/kg was effective in the treatment of most refractory UC. However, a 7-year follow-up of these patients found that only 12% could avoid colectomy. This suggests that cyclosporine treatment strategies are very effective for inducing remission in refractory UC, however, subsequently, when appropriate, elective surgery should be considered in this group of patients. Because the effective concentration range of CsA is narrow (100 ng/ml to 200 ng/m1), its use requires close monitoring of blood levels. For patients with effective CsA therapy, switch to oral after remission and transition to maintenance of thiopurines. When patients who do not respond after 5 to 7 days of CsA application should be promptly switched to treatment. (4) Biologic anti-tumor necrosis factor-α (TNF-α) monoclonal antibodies: including Infliximab (IFX) and adalimumab. IFX is a human-mouse chimeric IgGl monoclonal antibody, and adalimumab is a fully humanized IgGl-like monoclonal antibody that has also shown good efficacy and safety in patients who are resistant or intolerant to IFX. In 2005, a global, randomized, double-blind, controlled study showed that IFX is the treatment of choice for inducing remission in severe refractory UC, and can also be used for maintenance treatment, so IFX is recommended as a conversion therapy. “rescue” treatment option. For moderately active CD, IFX is recommended for patients who cannot tolerate conventional drug therapy, are hormone-dependent, or have failed hormone and immunosuppressive therapy; for severely active CD, IFX may be used when hormones are ineffective or may be used initially. induction of remission with IFX should be followed by maintenance therapy with IFX. the 2013 AGA guidelines strongly grade the recommendation for single-agent anti-TNF-α for moderate to severe CD-induced remission (moderate quality evidence level) and maintenance remission therapy (high quality evidence level). IFX recommends 5 mg/kg at weeks 0, 2, and 6 for remission induction; the same dose is then given at 8-week intervals for maintenance therapy. Because there is not enough clinical data to suggest when to discontinue IFX, maintenance therapy is currently recommended for 1 year, and discontinuation of IFX may be considered when clinical symptoms resolve with mucosal healing and normal C reactive protein (CRP) after hormone withdrawal.