Known brand names include Tylenol, Mapap, and Panadol.
A pain reliever and fever reducer, taken by mouth over the counter or given IV in the hospital. Too much, including from combination products that also contain it, can cause severe liver damage.
Exactly how acetaminophen eases pain and lowers fever is not known. It is thought to work mainly in the brain and spinal cord, changing how the body senses pain and helping it cool down. The liver breaks most of it down into forms that pass out in the urine. A small part becomes a harmful byproduct, which the liver normally neutralizes quickly at usual doses.
It does not change how platelets clump, and in people with hemophilia, repeated doses by mouth did not lengthen bleeding time. Given by IV, it reaches its highest blood level at the end of the 15 minute infusion. Taking more than the recommended amount, often by combining products that contain it, can cause liver failure and death. Signs of liver injury after an overdose may not appear until 48 to 72 hours later.
Acetaminophen relieves minor aches and pains, such as headache, backache, toothache, muscle aches, menstrual cramps, arthritis pain, and the aches of a cold. It also brings down a fever. As an IV infusion, it treats mild to moderate pain on its own and moderate to severe pain when given along with an opioid.
The tablets are available without a prescription and are taken by mouth. The IV form is given in the hospital, for pain in adults and children 2 years and older and for fever in adults and children. The tablet label says to stop and ask a doctor if pain lasts more than 10 days, fever lasts more than 3 days, or new symptoms appear. It should not be combined with any other product that contains the same medicine.
At normal doses most people notice nothing. In the hospital, nausea, vomiting, headache, and trouble sleeping were the most common complaints, and children also had constipation and itching. The label treats liver damage from taking too much as the main danger, and it warns about rare severe skin reactions and serious allergic reactions.
This is the boxed warning, the warning the FDA label prints first.
IV: risk of medication errors and hepatotoxicity. Dosing errors, such as confusing mg with mL, weight-based errors under 50 kg, or misprogrammed pumps, can cause accidental overdose and death. Acetaminophen has caused acute liver failure, sometimes leading to transplant or death, mostly at doses above the daily maximum and often from more than one acetaminophen product.
Sources: [1]