Many Prescription and Over-the-Counter Drugs May Harm Liver
August 15, 2001
In the last several years, the pharmaceutical industry has introduced many groundbreaking drugs. In increasing numbers though, both prescription and over-the-counter drugs are being linked to serious liver damage. According to Food and Drug Administration (FDA) officials, drug-related liver damage is the most common problem new drugs face once they enter the marketplace. The clinical trials that prospective drugs undergo prior to approval are generally too small to detect a drug's impact on the liver.
Liver failure, also known as hepatotoxicty, occurs in 2,000 adults and 90 children annually in the United States. More commonly, drugs cause less severe liver damage, which often goes undetected and thus unreported.
Alarmed by increasing reports of drug related liver failure, the FDA is improving technology used in the drug approval process in order to better understand and anticipate the toxic characteristics of prospective drugs. Currently, researchers monitor liver enzymes during clinical trials to detect liver toxicity. However, some experts doubt the effectiveness of this technique and suggest looking for a combination of elevated liver enzymes and high levels of bilirubin, a substance that indicates problems with liver functioning.
In recent years, several prominent drugs have been recalled or withdrawn after being associated with liver failure. The most notable recall is that of the diabetes drug Rezulin. It was prescribed to over 1.5 million diabetics between its introduction in 1997 and its withdrawal in March 2000. Although it was effective in treating diabetes, it caused 90 cases of liver failure and at least 63 deaths.
The liver breaks down chemicals in the body that are not water soluble, including many medications. It coverts these chemicals into substances the body can excrete. However, some chemicals are toxic to the liver, these substances destroy liver cells and may lead to liver problems and eventually liver failure.
Besides Rezulin, other prescription drugs, including painkiller Duract and the antibiotic Trovan, have been recalled or their sales severely limited due to reported liver problems. In a surprise to many, the popular over-the-counter painkiller and fever reducer acetaminophen, the main ingredient in Tylenol, is responsible for nearly 800 cases of acute liver failure and at least 85 deaths.
Acetaminophen is the only substance known to be toxic to everyone's liver at certain doses. Chronic drinkers are at especially high risk of liver damage caused by acetaminophen.
Childhood acetaminophen poisoning is less common because children do not take the drug as often as adults. However, liver toxicity may occur if the child is given an adult dose of Tylenol or more than the maximum childhood dose over a period of several days, thus allowing the toxins to accumulate in the liver.
Scientists are frustrated that they cannot accurately predict which drugs will negatively impact the liver. Until technology improves, FDA officials must weigh the risks of approving a new drug against the drug's therapeutic benefits.
For instance, in the case of the tuberculosis drug isoniazid, the benefits clearly outweigh the risks. Although the drug is known to cause liver problems, it is the best tuberculosis drug introduced to date, and thus isoniazid remains on the market.
In cases such as isoniazid, patients who receive the drug are informed of its potential to cause liver damage. In addition, doctors require that isoniazid patients undergo periodic liver function tests in order to closely monitor the body's reaction to the drug.
Besides prescription and over-the-counter drugs, several herbs and vitamins are known to interfere with liver functioning. Taking high doses of comfrey, jin bu huan, germander, ma huang (ephedra), mistletoe, pennyroyal, and vitamin A can all lead to liver injury. Illicit drugs such as ecstasy and cocaine also interfere with liver functioning.
-- Article Courtesy of InjuryBoard.com
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