Most of the enzymes involved in drug metabolism are present in the liver. This means the liver plays a key role in drug metabolism.

Drug metabolism occurs when the body chemically alters drugs so it can excrete them.

When a person takes certain medications, the body chemically alters the compounds in the drugs. These changes make the drugs more water soluble so that the body can excrete them.

These chemical alterations most commonly occur in the liver. Medical professionals refer to these alterations as biotransformations.

When drug metabolism occurs in the liver, it produces water-soluble compounds. The liver can then excrete these compounds in bile.

In this article, we discuss the role the liver plays in drug metabolism. We also outline the other functions of the liver and explain what metabolism is.

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The body uses enzymes in drug metabolism. The enzymes involved in drug metabolism are present in many tissues around the body but are most commonly present in the liver.

Individuals with liver disease may have difficulty metabolizing drugs. Liver impairment can result in issues with adequate drug excretion and persistently elevated serum drug levels. From there, drug toxicity can occur, which can further damage the liver and other vital organs.

The liver carries out this metabolism through complex processes that make use of cytochrome P450 enzymes. The liver carries out phase 1 and phase 2 reactions to metabolize these drugs.

Phase 1 reactions make use of the following types of reactions:

  • oxidation
  • reduction
  • hydrolysis

Then, during phase 2 reactions, the liver carries out conjugative reactions to alter the compounds.

Once the liver has metabolized the drugs, producing water-soluble compounds, it excretes them in bile, and the body can then excrete them in feces.

The liver is a critical organ in the body. It plays a role in several functions that help support:

Bile production

One of the main roles of the liver is to create and secrete bile. The body then stores the secreted bile in the gallbladder.

Bile helps with digestion, breaking down fats into fatty acids. This then allows the fatty acids to absorb into the bloodstream.

Fat-soluble vitamin storage and metabolism

Fat-soluble vitamins commonly reach the liver via intestinal absorption. The liver then stores or metabolizes these fat-soluble vitamins.

The liver stores these vitamins so the body can use them in the future.

Bilirubin metabolism

Bilirubin is a liquid that is yellow and brown. The body produces bilirubin when it breaks down red blood cells.

The liver metabolizes bilirubin, which it then secretes into a person’s bile. The liver also dissolves small amounts of bilirubin into the blood, where the kidneys filter it out.

When bilirubin enters a person’s bile, the intestinal wall cannot absorb it. This means that the body excretes most of this substance in feces.

Other functions of the liver

The liver also plays a role in thyroid hormone function. This is the hormone affects a number of systems in the body, including the:

The liver also manages the creation of plasma proteins in the body. These proteins can play a role in helping blood clot and fighting infections.

Metabolism is the term for all of the reactions that occur within each cell in the body to provide the body with energy.

These different biochemical processes help the body in a number of ways. They can help a person:

  • grow
  • reproduce
  • repair bodily damage
  • respond to their environment

Drug metabolism specifically occurs for the body to alter the compounds in drugs chemically. The body metabolizes these drugs to excrete them easily.

Most of these chemical alterations occur in the liver.

The following are some questions people frequently ask about the liver and drug metabolism.

Is the liver the main organ responsible for drug metabolism?

Yes, the liver is the main organ responsible for drug metabolism.

The enzymes that the body uses to metabolize drugs are present throughout the body but are most abundant in the liver.

Can drugs cause damage to the liver?

Certain drugs can cause liver dysfunction and liver damage to occur. This may even lead to organ failure.

This failure may occur through the drug’s direct effect on the liver or due to it altering liver blood flow.

Medical professionals may refer to this as drug-induced hepatotoxicity or drug-induced liver injury (DILI).

In the United States, DILI is the most common cause of acute liver failure.

The metabolism of drugs is the process where the body chemically alters the drugs so it can excrete them.

The liver plays a key role in the metabolism of drugs. The liver carries out phase 1 and phase 2 reactions to chemically alter drugs, making them more water-soluble.

This organ then excretes these compounds in bile. Once in the bile, the body then excretes these compounds in feces.

In some cases, drugs can have a negative effect on the liver. This can cause a person to develop DILI, which can lead to liver damage and even liver failure.