Soft Tissue Pain Clinic
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Consider medications containing the active ingredient, paracetomol (also known as acetaminophen). Acetaminophen, commonly referred to as the brand name Tylenol (used by more than 200 million Americans a year), is not as safe as we all might think. Acetaminophen can be highly toxic. The use of Tylenol instead of aspirin to treat fevers in infants has greatly reduced the occurrence of Reye's syndrome, an often fatal form of liver failure. Ironically, however, taking too much Tylenol (an overdose) can also cause liver failure. At Parkland Memorial Hospital (where President Kennedy died) in Dallas, acetaminophen is for example the #1 cause of acute liver failure. The drug accounts for 100,000 calls to poison control centers, 56,000 emergency room visits, 26,000 hospitalizations, and 450 deaths annually. Back to the top The FDA approved acetaminophen in 1951. The fact that an accidental overdose of acetaminophen can result in liver toxicity, liver failure, and even death has been known for some time. In addition some people are more susceptible to acetaminophen toxicity and can experience liver damage even at the recommended dose. A study by the U.S. Food and Drug Administration (FDA) showed that about 20% of people with acetaminophen-related liver toxicity had taken less than the recommended daily amount. For other people, a dangerous dose is not much higher than the recommended dose—that is, the “window” between a therapeutic dose and a toxic dose is smaller for acetaminophen than it is for many other drugs. Some experts also believe that taking acetaminophen for several days in a row may cause a dangerous build-up of the drug in the body. In 2006, the American Liver Foundation stated that acetaminophen should not be taken for more than 3 consecutive days, and then only sporadically. Back to the top Acetaminophen belongs to a class of drugs called analgesics (pain relievers) and antipyretics (fever reducers). The exact mechanism of action of acetaminophen is not known. Mode of action is not completely understood, but is thought to act in the brain. It has very weak effects on the COX-1 and COX-2 systems (see NSAIDs below), and therefore it has minimal peripheral anti-inflammatory actions, and does not cause gastric ulceration. Recent research suggests that it may work through a newly discovered COX-3 enzyme system. Acetaminophen relieves pain by elevating the pain threshold, that is, by requiring a greater amount of pain to develop before a person feels it. It reduces fever through its action on the heat-regulating center of the brain. Specifically, it tells the center to lower the body's temperature when the temperature is elevated. Back to the top How Acetaminophen Harms the Liver ( i.e. the technical explaination ) Like many drugs, acetaminophen is metabolized by the liver. If the normal processing pathway is overwhelmed by a high dose, a different pathway known as the cytochrome P450 enzyme system kicks in. When this happens, a toxic metabolic byproduct called NAPQI is produced that can kill liver cells. Alcohol and many other drugs also use the cytochrome P450 processing system, and the risk of a “bottleneck” is greater if the liver has to deal with both acetaminophen and these other substances at the same time. Acetaminophen poisoning has three stages. During the first 12- 24 hours after taking the drug, a person may experience nausea and vomiting. During the second phase, from 24-48 hours, the person usually feels better. After 48-72 hours, however, liver enzyme (ALT and AST) levels start to rise, indicating liver injury. Back to the top Taking acetaminophen on an empty stomach causes a condition called acetaminophen toxicity. That alone kills 100 people every year. Toxicity occurs when your body cannot process the drug quickly enough. Acetaminophen, in itself, is a deadly poison to the human body. However, a healthy liver produces enzymes to counteract the poison. This is what gives us the analgesic effect that we all know and love from the drug. When someone is not receiving proper nutrition, the liver slows down on how quickly it can produce those enzymes. In turn, that leaves us with the poison in our systems. Alcohol consumption is another key factor in potential liver damage from the drug. Individuals regularly consuming excess amounts of alcohol can develop liver toxicity at lower levels of acetaminophen intake. This, too, has been known for some time. It is not recommended that you take any NSAID (non steroid anti inflammatory drug) like acetaminophen if you consume more than three alcoholic drinks per day. Aspirin, ibuprofen, and naproxen sodium (Aleve) are all counted in that category, That means no more popping a handful of Tylenol to alleviate that hangover. Patients with liver and kidney disease should also exercise caution in taking acetaminophen. Patients with overdoses of acetaminophen should seek emergency care immediately. Early treatment can prevent liver damage or death. The signs and symptoms of liver toxicity may not become apparent for 2-3 days after a toxic overdose. Back to the top The following tips can help prevent acetaminophen related liver toxicity: • Do not take more than the recommended dose of 4 grams within a 24-hour period (for example, 12 regular strength or 8 extra strength Tylenol tablets) • Do not take the full day’s dose at one time; space it out over the course of the day • Do not take acetaminophen for more than 10 days in a row • Avoid drinking alcohol; this is important for people with hepatitis whether or not they use acetaminophen • People who do consume 2-3 alcoholic drinks per day should not take more than half the usual recommended dose of acetaminophen (2 grams within 24 hours) • People with advanced liver fibrosis or cirrhosis should avoid acetaminophen • Write down how much acetaminophen you take, and when, if you have trouble remembering • Check the labels of all medications; small doses of acetaminophen in combination remedies can add up to big trouble. Web Reference: Tylenol Toxicity
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Aleve
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