Before taking two cold medicines or two painkillers together, read the ingredient list; acetaminophen (paracetamol) should come from only one of them, and if you took too much, go to the hospital the same day even if you feel fine

Cost

Free. Look at the ingredient list on each box, a minute or two.

What you get

Across 22 hospitals in the U.S., 662 cases of acute liver failure were registered consecutively over 6 years. Of these, 275 (42%) were caused by acetaminophen, with a median dose swallowed of 24 g. Among these 275 people, 131 (48%) had taken too much by accident rather than on purpose. Of those who took too much by accident, 38% had taken two or more medicines containing this ingredient at the same time. Of the 275, 27% died before getting a liver transplant, and 8% had a liver transplant. In 2020 the National Medical Products Administration (国家药监局) required over-the-counter drug inserts to state that overuse can cause serious liver damage and to recommend a maximum of 2 g a day. The insert must also say to avoid, as far as possible, using it together with drugs that contain acetaminophen or other fever-reducing painkillers. U.S. rules require these over-the-counter drugs to list three liver-damage situations first in the warnings: exceeding the maximum daily dose, taking it with other drugs containing acetaminophen, and drinking 3 or more alcoholic drinks a day while using it. The same announcement from the administration also requires the inserts of extended-release preparations to state that if an adult or child takes too much, whether or not they feel unwell, they must seek care immediately. The antidote is called N-acetylcysteine; the insert says to use it as early as possible, with satisfactory results within 12 hours and poorer results after 24 hours. A U.S. multicenter study from 1976 to 1985 followed 2540 overdose patients who received this antidote. Among patients judged by blood drug level to be at possible risk of liver damage, 6.1% of those who started treatment within 10 hours developed liver damage. Of those who started between 10 and 24 hours, 26.4% developed liver damage. Starting within 8 hours of the overdose gave protection no matter how high the blood level was.

Notes

Acetaminophen is also called paracetamol (扑热息痛). In the generic names of combination cold medicines, the characters “氨酚” (ānfēn, short for acetaminophen), as in “氨酚伪麻” and “氨咖黄敏”, mean the product contains it. If you are not sure, show the boxes to the pharmacist at the drugstore. Graded B because the U.S. figures are a case registry with no comparison group, so they can't show how many problems reading the ingredient list would prevent. The benefit is rated “large” because of the outcome: nearly 30% of acute liver failure cases died directly. The numbers showing that the earlier the antidote the better come from a multicenter observational study without randomization, which compared only with past cases.

Evidence grade

B : Supported by research but without a precise number, or based on small or single studies.

Sources

1. Larson AM, Polson J, Fontana RJ, et al.; Acute Liver Failure Study Group (2005). Acetaminophen-induced acute liver failure: results of a United States multicenter, prospective study. Hepatology, 42(6):1364-1372. https://doi.org/10.1002/hep.20948
2. National Medical Products Administration Announcement on revising the package inserts of immediate-release and extended-release acetaminophen preparations (No. 15 of 2020), with Annex 1 "Revision requirements for package inserts of prescription immediate-release acetaminophen preparations", Annex 2 "Revision requirements for package inserts of over-the-counter immediate-release acetaminophen preparations" and Annex 3 "Revision requirements for package inserts of extended-release acetaminophen preparations" (republished by the Hunan Provincial Medical Products Administration) [in Chinese]. http://mpa.hunan.gov.cn/mpa/xxgk/tzgg/wjtz/202003/t20200311_11809335.html
3. 21 CFR 201.326(a)(1)(iii)(A) Liver warning. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-C/part-201/subpart-G/section-201.326
4. Smilkstein MJ, Knapp GL, Kulig KW, Rumack BH (1988). Efficacy of oral N-acetylcysteine in the treatment of acetaminophen overdose: analysis of the national multicenter study (1976 to 1985). New England Journal of Medicine, 319(24):1557-1562. https://doi.org/10.1056/NEJM198812153192401
5. MedlinePlus. Acetaminophen (In case of emergency/overdose). https://medlineplus.gov/druginfo/meds/a681004.html

Translated from the Chinese original. Original book, section 34, tip 1. This section is about health and medicines. It is general information, not a substitute for a doctor’s diagnosis or prescription. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer