I. When to apply antipyretics? Axillary more than 37.3 ° C (or 37.5 ° C), defined as fever. It is further categorized into low fever 37.4~38°C; medium fever 38.1~39°C; high fever 39.1~41°C; and ultra-high fever: above 41°C. Fever of ≤1 week is considered acute fever. For patients with temperature below 38.5°C, if the mental state is good, antipyretic drugs can be withheld and physical cooling is sufficient. For patients over 38.5°C, antipyretic drugs should be applied to reduce energy consumption and avoid complications such as febrile convulsions. The World Health Organization (WHO) recommends two classic oral antipyretics that are safe for pediatric use: acetaminophen and ibuprofen. 1.Acetaminophen(Paracetamol,Tylenol): First choice, for children over 3 months old. Routine dosage for children: oral, 10-15mg/kg/times, once every 4-6h; children aged 3-12 years old should be applied less than 5 times every 24h, and the course of treatment should not be more than 5d. Rectal administration is no longer recommended for pediatric application. Acetaminophen is safe at reasonable doses, with occasional nausea, vomiting, sweating, and abdominal pain, and a few cases of dermatitis, granulocytopenia, and thrombocytopenia. Overdose can cause liver injury. Severe hepatic and renal insufficiency is prohibited. Use with caution in children with liver disease or viral hepatitis, hepatic and renal insufficiency, severe cardiopulmonary disorders, and G-6-PD deficiency. Some compound preparations often contain “acetaminophen” as an ingredient, such as aminophenol alkylamine granules, aminophenol xanthamin granules, aminophenol mephedrone syrup, aminophenol mephedrone suspension and so on, but paracetamol and tylenol are single preparations. It is important to avoid duplication of medication when taking them. 2, Ibuprofen (Merrill): for children over 6 months of age. Single preparations include Merrill and Fen-Phen. The recommended dosage of ibuprofen for children is 5-10mg/kg every 6 hours, up to 4 times every 24h. Ibuprofen has a strong antipyretic effect, and the process of antipyretic may cause the body to sweat a lot, so when using ibuprofen to reduce fever, you need to pay attention to whether the child is dehydrated, insufficient intake, etc., and can be rehydrated through the vein if necessary. Ibuprofen is excreted through the kidneys and should be used with caution in patients with poor kidney function. Ibuprofen is safe to use according to the recommended dosage, and the common adverse reaction is gastrointestinal adverse reaction. children with G-6-PD deficiency can use “ibuprofen”. Lysergic acid: It is the compound salt of aspirin and lysine, and its mechanism of action is the same as that of aspirin. Intravenous or intramuscular administration, reducing or avoiding the occurrence of gastrointestinal reactions, strong antipyretic effect, fast onset of action, slow and gentle, can be used as a common pediatric antipyretic drugs. It can be used for children who are prone to convulsions due to high fever and cannot take the drug orally. However, long-term application may induce Reye’s syndrome may even induce anaphylaxis and asthma severe attack. Used for intravenous antipyretic, the dose is generally 10-20mg/kg, 24 hours shall not be more than 4 times, the interval shall not be less than 4h. 4, aspirin: traditional antipyretic and analgesic, the World Health Organization does not recommend aspirin routinely used for pediatric fever, it is recommended to change to other categories of antipyretic drugs. China’s pediatrics has been basically not such drugs for fever, only for some special diseases, such as Kawasaki disease, rheumatic fever, juvenile arthritis and other treatments. 5, diclofenac: a new type of potent anti-inflammatory and analgesic drugs, it inhibits prostate synthesis and play its pharmacological role, with anti-rheumatic, anti-inflammatory, analgesic and antipyretic effect, analgesic, anti-inflammatory and antipyretic effect than indomethacin 2 to 2.5 times stronger than aspirin 26 to 50 times stronger than aspirin, strong, less adverse effects, small dose, small individual differences, for a variety of inflammation caused by fever. There is a view that children under 14 years of age are prohibited. 6, nimesulide: new non-steroidal anti-inflammatory, analgesic, antipyretic drugs, the pharmacological effect is to inhibit the activity of cyclooxygenase, blocking the biosynthesis of prostaglandin-like substances, leukocyte release of media and polymorphonuclear leukocytes oxidation reaction, so as to play the role of fever, anti-inflammatory effect, used for upper respiratory tract infections caused by fever, the effect can last for 6 to 8 hours. 2011, the media in February reported a number of fatal cases. In February 2011, the media reported a number of fatal cases, and later called it a “life-threatening antipyretic”.In May 2011, the State Drug Administration issued a notice restricting the application of nimesulide, “prohibiting its oral preparation to be used in children under 12 years of age”.