Last updated: October 29, 2014
Trade Names: Include Acephen, Aspirin-free Anacin, Tylenol, Tylenol Arthritis
Drug Class: Analgesic/antipyretic
Capsules: 325 and 500 mg (extra strength)
Tablets: 120, 160, 325, 500 mg; 650 mg (extended-release)
Suppositories: 80, 120, 325, 650 mg
Elixir, suspension, liquid, or syrup: 100 mg/mL and 160 mg/5 mL
Dose: Adults, 1–3 g/day in three to four divided doses; do not exceed total daily dose of 4 g/day from all sources. Some experts believe the maximum daily dose of acetaminophen should be limited to 3 g/day.
Indications: Pain, musculoskeletal pain, headache, fever; less likely to cause GI ulceration than NSAIDs
Mechanism of Action: Uncertain; may inhibit COX-2 and central prostaglandin synthesis
Contraindications: Hypersensitivity to acetaminophen
Precautions: Concomitant alcohol use, liver disease and fasting may increase the risk of acetaminophen hepatotoxicity. Avoid or use lower doses with caution in liver disease (usually <2 g/day). Avoid concomitant alcohol. May cause severe hepatotoxicity in overdose. Patients must avoid self-medication with OTC preparations that may also contain acetaminophen.
Pregnancy Risk: B
Adverse Effects: Rarely causes allergy, Stevens-Johnson syndrome, rash, or agranulocytosis. Hepatotoxicity is rare at therapeutic doses. Overdose (usually >8 g/day) causes delayed (48–72 hours) and potentially fatal hepatotoxicity. Controversial evidence links chronic use to increased risk of renal impairment.
Alcohol: Increases risk of hepatotoxicity
Warfarin: Acetaminophen (>2 g/day) may increase anticoagulant effect Barbiturates, carbamazepine, hydantoins, and sulfinpyrazone: May increase hepatotoxicity of acetaminophen
Patient Instructions: Do not exceed prescribed dose; do not take additional OTC or prescription medications that contain acetaminophen; do not drink alcohol.
Clinical Pharmacology: Rapid complete oral absorption; 95% metabolized in the liver (mainly conjugation). Duration of action is 4–6 hours. With overdose, a hepatotoxic metabolite accumulates.