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Acetaminophen is a centrally acting analgesic and anti-pyretic.
Acetaminophen is a centrally acting analgesic and anti-pyretic. It is used to treat many conditions such as headache, muscle aches, arthritis, backache, toothaches, colds, and fever. Acetaminophen is effective in the central nervous system and acts primarily in the CNS, increasing the pain threshold by inhibiting both isoforms of cyclooxygenase, COX-1, COX-2, and COX-3 enzymes involved in prostaglandin synthesis.
Pharmacological class: Analgesic/antipyretic
Acetaminophen acts primarily in the CNS, increasing the pain threshold by inhibiting both isoforms of cyclooxygenase, COX-1, COX-2, and COX-3 enzymes involved in prostaglandin (PG) synthesis. The antipyretic properties of acetaminophen are likely due to direct effects on the heat-regulating centers of the hypothalamus resulting in peripheral vasodilation, sweating and hence heat dissipation.
For adults and children 12 years of age and older: 650 to 1000 mg every 4 to 6 hours
For children under 12 years of age: 10 to 15 mg/kg every 4 to 6 hours
Acetaminophen is rapidly and almost completely absorbed. It primarily undergoes glucuronidation (45-55% of the dose) in which this process is facilitated by UGT1A1, UGT1A6, UGT1A9, UGT2B15 in the liver or UGT1A10 in the gut. 30-35% of the dose undergoes sulfation. This biotransformation is facilitated by SULT1A1, SULT1A3, SULT1A4, SULT1E1 and SULT2A1. A small percentage of acetaminophen is oxidized by CYP2E1 to form N-acetyl-p-benzo-quinone imine (NAPQI), a toxic metabolite which is then conjugated to glutathione and excreted renally. Approximately 80% of acetaminophen is excreted in the urine after conjugation and about 3% is excreted unchanged.
Common (affecting between 1 in 10 to 1 in 100):
Uncommon (affecting 1 in 100 to 1 in 1000):
Very rare (affecting less than 1 in 10,000):
Seventeen blinded, randomized controlled trials with children (<18 years) receiving either ibuprofen or acetaminophen to treat fever or moderate to severe pain were considered. Ibuprofen (4-10 mg/kg) and acetaminophen (7-15 mg/kg) showed comparable efficacy (3 pain relief trials; 186 children). The risk ratio point estimates were 1.14 (95%confidence interval [CI], 0.82-1.58) at 2 hours after receiving the dose, and 1.11 (95% CI, 0.89-1.38) at 4 hours. Acetaminophen reduced the temperature (10-15 mg/kg) at 2, 4, and 6 hours after treatment. Single doses of ibuprofen (4-10 mg/kg) and acetaminophen (7-15 mg/kg) have similar efficacy for relieving moderate to severe pain and fever. Acetaminophen was effective at (10-15 mg/kg) at 2, 4, and 6 hours post-treatment.
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