It is the most commonly used non anti-inflammatory antipyretic analgesic. Its antipyretic effect is similar to that of aspirin. It has weak analgesic effect and no anti-inflammatory and anti rheumatic effect. It is the best variety of acetanilide drugs. It is especially suitable for patients who cannot use carboxylic acid drugs. For cold, toothache and other diseases. Acetaminophen is also an intermediate in organic synthesis, a stabilizer for hydrogen peroxide and a photographic chemical.
Uses
It is mainly used for fever, headache caused by cold and relieving mild and moderate pain, such as joint pain, muscle pain, neuralgia, migraine, dysmenorrhea, cancer pain and postoperative analgesia. It can also be used for patients who are allergic, intolerant or unsuitable for aspirin: such as patients with chickenpox, hemophilia and other hemorrhagic diseases (including patients treated with anticoagulation), as well as patients with mild peptic ulcer and gastritis.
Pharmacological action
By inhibiting cyclooxygenase, it selectively inhibits the synthesis of prostaglandins in the hypothalamic thermoregulatory center, resulting in peripheral vasodilation and sweating, and its antipyretic effect is similar to that of aspirin; It plays an analgesic role by inhibiting the synthesis and release of prostaglandins and improving the pain threshold. It is a peripheral analgesic. Its effect is weaker than aspirin and is only effective for mild and moderate pain. This product has no obvious anti-inflammatory effect. After oral administration, it is absorbed rapidly and completely from the gastrointestinal tract (taking medicine after a high carbohydrate diet may reduce absorption). After absorption, it is evenly distributed in the body fluid, and about 25% of it binds to plasma protein. Small dose (blood concentration < 60 μ G / ml) does not bind to protein obviously, and the binding rate is higher in large amount or toxic amount, up to 43%. 90 ~ 95% of the product is metabolized in the liver and is mainly combined with glucuronic acid, sulfuric acid and cysteine. Intermediate metabolites have toxic effects on the liver.
Preparation method
Acetaminophen is obtained by acetylation. Method 1: add p-aminophenol into dilute acetic acid, then add glacial acetic acid, raise the temperature to 150 ℃ for reaction for 7h, add acetic anhydride, and then react for 2h. Check the end point. After passing the test, cool to below 25 ℃, shake and filter, wash with water until there is no acetic acid smell, shake and dry to obtain the crude product. Method 2: p-aminophenol, glacial acetic acid and acid mother liquor containing more than 50% acid are distilled together. The speed of steaming out dilute acid is one tenth of the total amount distilled per hour. When the internal temperature rises to more than 130 ℃, sample and check that the residual amount of p-aminophenol is less than 2.5%. Add dilute acid (content more than 50%) and cool and crystallize. After filtration, wash with a small amount of dilute acid and then wash with a large amount of water until the filtrate is nearly colorless to obtain the crude product. The yield of method 1 is 90%, and the yield of method 2 is 90-95%. Refining method: heat the water to near boiling and put in the crude product. Heat up to full solution, add activated carbon soaked in water, adjust to pH = 4.2-4.6 with dilute acetic acid, and boil for 10min. Press filtration, add a small amount of sodium bisulfite to the filtrate. Cool to below 20 ℃ and precipitate crystallization. Filter, wash and dry to obtain the finished product of paracetamol. Other production methods include: (1) reduction of p-nitrophenol with zinc in glacial acetic acid and acetylation to obtain p-acetaminophen; (2) The hydrazone produced by p-hydroxyacetophenone is placed in sulfuric acid solution, and sodium nitrite is added to produce p-acetaminophen
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