Acetaminophen (Tylenol) is used to treat moderate to mild pain and fever and often is used in place of the NSAIDs or salicylates. It is the most frequently used drug for managing pain and fever in children. It is widely available over the counter and is found in many combination products. It can be extremely toxic. It causes severe liver toxicity that can lead to death when taken in high doses. Every year children die from inadvertent acetaminophen overdose when parents give their child more than one OTC drug containing acetaminophen or administer a high dose of acetaminophen.
Acetaminophen acts directly on the thermoregulatory cells in the hypothalamus to cause sweating and vasodilation; this in turn causes the release of heat and lowers fever. The mechanism of action related to the analgesic effects of acetaminophen has not been identified.
Acetaminophen is indicated for the treatment of pain and fever associated with a variety of conditions, including influenza; for the prophylaxis of children receiving diphtheria–pertussis–tetanus (DPT) immunizations (aspirin may mask Reye syndrome in children); and for the relief of musculoskeletal pain associated with arthritis.
Acetaminophen is rapidly absorbed from the GI tract, reaching peak levels in 0.5 to 2 hours. It is extensively metabolized in the liver and excreted in the urine, with a half-life of about 2 hours. Caution should be used in patients with hepatic or renal impairment, which could interfere with metabolism and excretion of the drug, leading to toxic levels. Acetaminophen crosses the placenta and enters breast milk; it should be used cautiously during pregnancy or lactation because of the potential adverse effects on the fetus or neonate.
Acetaminophen is contraindicated in the presence of allergy to acetaminophen. It should be used cautiously in pregnancy or lactation and in hepatic dysfunction or chronic alcoholism because of associated toxic effects on the liver.
Adverse effects associated with acetaminophen use include headache, hemolytic anemia, renal dysfunction, skin rash, and fever. Hepatotoxicity is a potentially fatal adverse effect that is usually associated with chronic use and overdose and is related to direct toxic effects on the liver. The dose that could prove toxic varies with the age of the patient, other drugs that the patient might be taking, and the underlying hepatic function of that patient. When overdose occurs, acetylcysteine can be used as an antidote. Life support measures may also be necessary.
Clinically Important Drug–Drug Interactions
临床上重要的药药相互作用
There is an increased risk of bleeding with oral anticoagulants because of effects on the liver; of toxicity with chronic ethanol ingestion because of toxic effects on the liver; and of hepatotoxicity with barbiturates, carbamazepine, hydantoins, rifampin, or sulfinpyrazone. These combinations should be avoided, but if they must be used, appropriate dose adjustment should be made and the patient should be monitored closely.
acetaminophen – n. 醋氨酚
Tylenol – n. 泰诺林
inadvertent – a. 非故意的，疏忽的
thermoregulatory – a. 体温调节的
hypothalamus – n. 下丘脑
prophylaxis – n. 预防
DPT -- diphtheria–pertussis–tetanus 白百破
hemolytic – a. 溶血的
hepatotoxicity – n. 肝毒性
overdose – n. （服药）过量
acetylcysteine – n. 乙酰半胱氨酸
antidote – n. 解毒药
barbiturates – n. 巴比妥酸盐类
carbamazepine – n. 卡马西平
hydantoin – n. 乙内酰脲类
rifampin – n. 利福平
sulfinpyrazone – n. 磺吡酮
1. A 26-year-old man presents to the emergency department with severe right lower quadrant pain. Physical exam reveals rebound tenderness and decreased bowel sounds. An emergent appendectomy is performed. Postsurgically, he is given an NSAID along with morphine for pain control. Which of the following NSAIDs is commonly used as an adjunct to opioids postsurgically?
A. Acetaminophen
B. Celecoxib
C. Ibuprofen
D. Ketorolac
2. A 29-year-old woman has a positive pregnancy test. She presents to her primary care physician for confirmation. She has a history of recurrent urinary tract infections, headaches, seizure disorder, and pulmonary embolus. Her current medications include acetaminophen, ciprofloxacin, warfarin, valproic acid, and methotrexate. Which of the following medications could be maintained at its current dose during her pregnancy?
A. Acetaminophen
B. Ciprofloxacin
C. Methotrexate
D. Valproic acid
1. D: Ketorolac.
Ketorolac is an NSAID but has poor anti-inflammatory properties. Its main use is as an analgesic and can be used in place of or in addition to opioids. It carries a high risk of toxicity and should not be used for more than 5 days in any patient. 2. A: Acetaminophen.
Analgesics such as acetaminophen, ibuprofen, and codeine are considered safe during pregnancy. Antibiotics such as penicillins, erythromycin, and cephalosporins are also considered safe in pregnancy. These medications usually do not require dose adjustments.
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