Chemical and Drug Induced Liver Injury

What Chemicals and Drugs Damage the Liver?

Many chemicals that are inhaled or swallowed can damage the liver. Among these are drugs, industrial solvents and pollutants. Almost every known drug has at one time or another been implicated as a cause of liver damage.

Chemicals which damage the liver fall onto two groups:

(1) Predictable liver toxins - These damage the liver regularly following exposure to a certain amount of the substance.

(2) Unpredictable liver toxins - These cause damage in only a small percentage of people exposed to them.


Why is the Liver so Susceptible to Injury by Chemicals and Drugs?

The reason seems to be linked to the liver's unique function of processing the chemicals and drugs which enter the blood stream. Many of these chemicals are difficult for the kidneys to excrete out of the body. The liver helps by removing these chemicals from the blood stream and changing them into products that can be readily removed through the bile or urine. In this process, unstable toxic products are sometimes produced. These can attack and injure the liver. Predictable toxic chemical injury usually involves this type of mechanism. Examples are the cleaning solvent, carbon tetrachloride, and the pain medication, acetaminophen. Acetaminophen is present in many over-the-counter and prescription pain killers (e.g. Tylenol, Nyquil, Percocet, Excedrin, Darvocet, Vicodin) and is usually safe when taken as prescribed. When acetaminophen is taken in excessive doses, either at once or over a period of time, severe damage to the liver may occur. Acetaminophen is toxic at lower doses in individuals who are regular, excessive (over two drinks each day) consumers of alcohol, which is also toxic to the liver. In fact, alcohol is by far the most common cause of toxic chemical damage to the liver in our society.

The unpredictable type injury can be produced by many drugs and appears to involve an allergic reaction that is directed at the liver. Many different medicinal drugs (e.g. antibiotics, seizure medications and anesthetics) can cause this type of reaction in susceptible individuals.


What are the Symptoms of this Type of Liver Injury?

Symptoms of chemical injury to the liver can resemble any form of acute or chronic liver disease. Acute liver injury can resemble viral hepatitis or blockage of the bile ducts. In other cases, a patient with fever, abdominal pain and jaundice may have a form of chemical injury that can be confused with conditions such as stones blocking the bile ducts that may require other surgery. Chemicals can also cause chronic liver disease and cirrhosis. Usually, chronic liver disease develops only after long-term use of the drug. Excessive exposure to certain drugs and chemicals may cause tumors of the liver. An important example is the group of drugs known as anabolic steroids, best known for their use in body building.


Can Illegal Drugs Harm the Liver?

Liver damage is common in people who are regular, illegal drug users. Most instances of liver damage in these individuals result from viral hepatitis caused by sharing contaminated needles and using alcohol. However, certain commonly abused drugs (e.g. cocaine) may be capable of producing liver damage.


How is the Diagnosis of Chemical Liver Injury Made?

Usually it must be based on circumstantial evidence, as there are no specific tests. In any patient with liver disease, close attention needs to be given to the drugs used and the environmental and occupational exposures. No chemical is too trivial to be considered. Timing may be helpful, since many forms of chemical liver injury will occur days to weeks after the first exposure. However, there are exceptions in which a drug is taken for many months before liver injury or exposure to the toxic substance. In most cases, there will be rapid improvement in days or weeks after removal of the chemical. When drug allergy is involved, giving the patient the drug again will lead to a rapid worsening of the liver disease. This is a conclusive test, but is rarely justified because of the risk to the patient.

Even if chronic liver disease has developed, removal of exposure to the offending chemical or drug can lead to rapid improvement. Usually, no other specific therapy is needed. If there is any concern regarding a particular drug or chemical, a physician or poison control center (located in major hospital centers) should be consulted.

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