Acetaminophen, the active ingredient in Tylenol, is the most widely used medication in the United States. However, it's also the most common medication overdose reported to poison control centers. If taken in proper amounts, it is a safe and effective medicine for pain due to a variety of causes, as well as for reducing fever. Too much acetaminophen, however, can lead to liver damage, which can occasionally be fatal.
Avoiding Toxicity
Acetaminophen is present in many over-the-counter (OTC) medications used for pain, colds, flu, sleeplessness, migraines and allergies. Though is it listed as an active ingredient in the labeling of these preparations, the inattentive consumer may be unaware of its presence and accidentally ingest too much if taken with Tylenol itself or with other medications containing acetaminophen.
Many prescription pain relievers contain acetaminophen, such as Vicodin, Percocet, Lortab and Darvocet. Prescription labels usually do not include ingredients, though occasionally the abbreviation for acetaminophen, "APAP," may be seen. Patients taking a prescription pain reliever should ask their physician or pharmacist if acetaminophen is present in the formulation. The maximum total dose of acetaminophen that should be taken in any 24-hour period by adults is 4 g (or 4,000 mg). This is the equivalent of two extra-strength Tylenols taken four times daily.
Patients at Risk
Chronic alcoholics are more prone to developing acetaminophen-related liver toxicity, whereas liver damage is somewhat less common in young children.
Symptoms
According to an article in the journal "Chest," there are four classic stages of acetaminophen overdose. Stage 1 occurs within 24 hours after an excessive ingestion of acetaminophen, and is marked by symptoms such as nausea, vomiting, lack of appetite, malaise and sweating. Some patients may not have any symptoms during this time. During stage 2, which occurs one to two days following acute ingestion, stage 1 symptoms tend to disappear and are replaced by pain in the upper right abdomen. Laboratory tests used to monitor liver function start to become abnormal. Stage 3 occurs after three to five days, and is marked by symptoms of liver damage, such as jaundice (yellowing of the skin), low blood sugar, blood clotting abnormalities, diminished alertness and possible kidney failure. Some of the symptoms of stage 1 may re-appear. Liver function tests are markedly abnormal. During stage 4, occurring four to five days after ingestion, the patient will either begin a full recovery typically without lasting liver damage, will require a liver transplant or will die of complete liver failure.
Treatment
Fortunately, an antidote exists for the treatment of acetaminophen toxicity, but should be started early after ingestion for maximum effectiveness. Therefore, if you suspect acetaminophen overuse, whether it be accidental or intentional, be sure to get evaluated in an emergency facility, even if symptoms are mild or absent. The antidote, acetylcysteine (brand names Mucomyst and Acetadote), can be given by mouth or injection if blood levels of acetaminophen are sufficiently high.
Outcome
Fortunately, most cases of acetaminophen toxicity are not serious and leave no permanent effects. Only a small percentage of patients require treatment with an antidote, and even fewer develop severe liver damage. However, if the liver is destroyed by acetaminophen, a liver transplant is necessary to prevent death.
References
- "Chest"; Adult Toxicology in Critcal Care: Part II: Specific Poisonings; Mokhlesi JB, et al.; March 2003
- "PowerPak"; Avoiding Acetaminophen Toxicity: The Pharmacist's Role in Safety and Patient Education; Lea S. Eiland, et al.; October 2009
- "Pharmacotherapy: A Pathophysiologic Approach"; DiPiro JT, Talbert RL, Yee, GC, et al. (eds.); 2005
- "AHFS Drug Information"; McEvoy GK (ed.); 2009
