The difference between thymopentin and thymopentin is the drug composition, and the skin test prior to injection use. 1. Drug composition: thymopentapeptide commonly used dosage form for injection, the drug composition is mainly lysyl, argininyl, valinyl, aspartyl, tyrosine. Thymic peptide commonly used dosage form of injection, tablets, capsules, etc., the drug composition is thymus α1 and other small molecule peptides. 2. Skin test before injection use: Thymopentin for injection needs skin test before use. Thymopeptide injection does not need skin test before use. Thymopentin and Thymopeptide are both immunomodulators and are used in the treatment of certain autoimmune diseases, various T-cell deficient diseases, and various cellular immunodeficiency diseases. Adverse reactions can be seen as fever, dizziness, chest tightness, nausea, and weakness. Both drugs are contraindicated for those who have allergic reaction to the product, or who need immunosuppression at the initial stage of organ transplantation. Specific need to follow the doctor’s instructions to use the drug.