Pharmacology · Class
Non-opioid analgesic antipyretics !
Medicines that ease pain and bring down fever with little or no anti-inflammatory effect, such as paracetamol and metamizole.
Updated 2026-11-01
What they are
A group of non-opioid analgesics and antipyretics kept apart from the NSAIDs because, at usual doses, they barely reduce inflammation or harm the stomach lining. Its two members are paracetamol (acetaminophen), the most widely used antipyretic in the world, and metamizole (dipyrone), which is not approved in the United States because of its adverse reactions but is still used in many other countries.
Mechanism of action
Their mechanism is not fully settled. Paracetamol weakly inhibits the cyclooxygenases, above all in the central nervous system, where the peroxide tone is low; in inflamed tissue, rich in peroxides, it loses that effect, which is why it hardly reduces inflammation or affects platelets. Metamizole is a prodrug: its active metabolites reduce prostaglandin-driven hyperalgesia and also relax smooth muscle.
Drugs in this class
- ParacetamolThe most widely used painkiller and fever reducer. Safe at correct doses, but overdose destroys the liver; its…Cyclooxygenases, mainly in the central nervous system (mechanism not fully established)
- MetamizoleA strong analgesic and antipyretic that also relaxes smooth muscle. Its serious risk is agranulocytosis, unrelated to…Active metabolites that reduce prostaglandin-driven hyperalgesia (mechanism not fully established)
Others in the class
- propyphenazone
Test yourself
Think of the answer, then tap the question to see it.
Why does paracetamol lower fever but hardly reduce inflammation?
It inhibits the cyclooxygenases only where the peroxide tone is low, as in the central nervous system; in inflamed, peroxide-rich tissue it loses that effect.
Which antipyretic is preferred for a patient with fever in an area where dengue circulates, and why?
Paracetamol, because NSAIDs such as ibuprofen or acetylsalicylic acid increase the risk of bleeding if the illness is dengue.
Which symptoms suggest agranulocytosis in a patient receiving metamizole?
Fever, chills, sore throat and painful sores on the mucous membranes (mouth, nose, throat, genital or anal area). The drug is stopped and a full blood count with differential is done at once.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Acetaminophen: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ACETAMINOPHEN injection, solution (DailyMed (U.S. National Library of Medicine), 2026); Metamizole-containing medicinal products - referral (European Medicines Agency, 2024); Metamizole (PubChem (NCBI), 2026).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.