ACETAMINOPHEN (TYLENOL).MODE OF ACTION Inhibits cyclo-oxygenase in the central nervous system, which inhibits prostaglandin synthesis. EFFECTS ON PAIN Used as an analgesic and antipyretic antipyretic /an·ti·py·ret·ic/ (-pi-ret´ik) 1. relieving or reducing fever. 2. an agent that so acts. an·ti·py·ret·ic n. An agent that reduces or prevents fever. . CONTRAINDICATIONS Known hypersensitivity to acetaminophen. Pregnancy Category B Pregnancy category B Animal studies indicate no fetal risk, but no human studies; or adverse effects in animals, but not in well-controlled human studies. Mentioned in: Antianxiety Drugs . ADVERSE EFFECTS Hemolytic anemia, thrombocytopenia, neutropenia, agranulocytosis agranulocytosis (əgrăn'yəlōsītō`sis), disease in which the production of granulated white blood cells by the bone marrow is impaired. , pancytopenia pancytopenia /pan·cy·to·pe·nia/ (-sit-ah-pe´ne-ah) abnormal depression of all the cellular elements of the blood. pan·cy·to·pe·ni·a n. , and leukopenia have been reported. Nephrotoxicity (especially with heavy use) and hepatotoxicity (especially with heavy use or concomitant alcohol consumption) have been reported. Rash, skin eruptions, and fever have been reported in hypersensitivity reactions. DRUG-DRUG INTERACTIONS Hepatotoxicity be increased with long-term combined use with barbiturates Barbiturates Definition Barbiturates are medicines that act on the central nervous system and cause drowsiness and can control seizures. Purpose (such as phenobarbital), carbamazepine, hydantoins (such as phenytoin phenytoin /phen·y·to·in/ (fen´i-toin?) an anticonvulsant used in the control of various kinds of epilepsy and of seizures associated with neurosurgery. phen·y·to·in n. ), isoniazid, rifampin, and sulfinpyrazone sulfinpyrazone /sul·fin·py·ra·zone/ (sul?fin-pi´rah-zon) a uricosuric agent used in the treatment of gout. Sulfinpyrazone A drug that corrects hyperuricemia by increasing the urinary excretion of urate. . Acetaminophen may increase the hypoprothrombinemic effect of warfarin. The INR should be monitored, especially if the patient consumes large quantities of acetaminophen. For pain relief in patients on warfarin therapy, acetaminophen remains a safer alternative to the nonsteroidal anti-inflammatory drugs Nonsteroidal Anti-Inflammatory Drugs Definition Nonsteroidal anti-inflammatory drugs are medicines that relieve pain, swelling, stiffness, and inflammation. . DRUG-FOOD INTERACTIONS May be taken with or without food, although food may slightly decrease absorption of acetaminophen. RECOMMENDED DOSE 650 mg every 4 to 6 hours. Do not exceed 4 grams in 24 hours. DOSAGE FORMS AVAILABLE Available in 325 mg, 500 mg, 650 mg tablets. Available in 80 mg, 120 mg, 125 mg, 300 mg, 325 mg, and 650 mg suppositories. Available in drops, liquid, elixir, and solutions in a variety of concentrations. MANUFACTURER McNeil and many others. OTHER POINTS OF INTEREST Patients who drink three or more alcoholic drinks per day may be at an increased risk of hepatotoxicity or gastrointestinal bleeding from use of acetaminophen or combination of acetaminophen with other analgesics/antipyretics. Overdosage may result in death through hepatic injury. The antidote for poisoning is N-acetylcysteine (Mucomyst). Gastric lavage is also recommended. References (1.) Hutchison TA, Shahan DR. Anderson ML (Eds): DRUGDEX System. MICROMEDEX, Inc., Englewood, Colorado (Edition expires 12/2000) (2.) Hebel SK, Katstrup EK (Eds): Drug Facts and Comparisons. St. Louis, Mo (2001) |
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