Possible reasons why fever does not go down after taking antipyretic drugs include drugs not taking effect, infection and other primary diseases not effectively controlled, central fever, tumors, connective tissue diseases, allergic diseases, endocrine and metabolic diseases, and so on. 1. Drugs do not work: Different antipyretic drugs have different working time, such as acetaminophen, ibuprofen and other antipyretic and analgesic drugs usually take about 1 hour to work after oral intake, and they may not work within a short period of time. 2. Infections and other primary diseases are not effectively controlled: If the primary bacterial infection is not effectively controlled, the use of antipyretic drugs is usually not effective in controlling the symptoms of fever, even if the fever can be controlled for a certain period of time, the fever will continue to appear after the effect of the drug has disappeared, and the use of antibiotics, such as cefuroxime, is needed to control the infection treatment. 3. Central fever: central fever caused by traumatic brain injury and cerebral hemorrhage, the use of general antipyretic drugs may be ineffective, because this kind of fever is caused by the disorder of thermoregulation center, and glucocorticoid such as dexamethasone can be replaced for treatment. 4. Tumor: if there are tumors such as lung cancer, breast cancer, esophageal cancer, leukemia, lymphoma, etc., which can not be intervened in time, and if they continue to secrete tumor necrosis factor and other thermogenic sources, fever will occur repeatedly. 5. Other diseases: connective tissue diseases such as systemic lupus erythematosus, dermatomyositis, polyarteritis nodosa, etc.; rheumatic fever, hemolytic reaction and other metabolic diseases; endocrine metabolic diseases such as hyperthyroidism, etc. will also take antipyretic medicines or do not reduce the fever. Treatment of the primary disease is required. If persistent fever occurs, it is recommended to go to the hospital in time. The above drugs need to be used under the guidance of clinicians.