The human liver is a vital organ that performs a wide variety of physiological functions in the body. In addition to acting as a detox center for the body, it is instrumental in the metabolism of food, the synthesis of proteins, and a number of important functions related to maintaining the body’s homeostasis. The liver does have its limits, however, and there are numerous substances that can threaten its health. One of the substances that has the potential for harm is the class of medications that are used for pain relief.

Overview of the Liver

The liver is the largest solid internal organ in the human body, located in the upper right portion of the abdomen, beneath the diaphragm and above the stomach. While the liver is primarily part of the digestive system, its functions affect many other organs and body systems. Because of how vital it is, humans can’t live without it, and liver damage or dysfunction can cause serious problems. Below are the main functions of the liver:

  • Metabolism: One of the most important digestive functions of the liver is the regulation of carbohydrate, lipid, and protein metabolism. It stores glucose in the form of glycogen and releases it into the bloodstream as needed to maintain stable blood sugar levels. Additionally, it synthesizes and metabolizes fats and proteins essential for various physiological processes.
  • Detoxification: Another important function of the liver is the removal of toxic substances from the bloodstream. When any potentially harmful substance—such as drugs, alcohol, metabolic waste products, and environmental toxins—enters the liver via the bloodstream, it metabolizes them in order to make them less toxic. Toxins are then eliminated through bile or urine.
  • Bile production: The liver produces bile, a fluid necessary for the digestion and absorption of fats in the small intestine. Bile is synthesized in liver cells and is transported to the gallbladder for storage and concentration before being released into the small intestine to aid in fat digestion.
  • Protein synthesis: The liver also synthesizes proteins that are essential for blood clotting, immune function, and the distribution of fluids.
  • Storage: Since nearly all blood in the body passes through the liver, it is also a storage area for glycogen and essential vitamins and minerals that support various metabolic processes.

Possible Liver Problems

There are also unfortunately many ways that these functions can be disrupted through various diseases and disorders. While some have a genetic component, many causes of reduced liver function or acute liver failure are related to dietary and lifestyle factors. Here are some of the more common problems that can affect the liver:

  • Hepatitis: Hepatitis is the term for inflammation of the liver, which can be caused by viral infections, autoimmune diseases, excessive alcohol use, medications, toxins, or metabolic disorders. The most common cause of hepatitis, however, is an infection by the viruses behind hepatitis B or hepatitis C.
  • Fatty liver disease: This condition is caused by excess fat accumulation in liver cells. It can be caused by obesity, insulin resistance, diabetes, high cholesterol or triglycerides, excessive alcohol consumption, or certain medications. The two main types are non-alcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (AFLD).
  • Cirrhosis: Liver cirrhosis is a kind of liver disease that involves extensive scarring (fibrosis) of liver tissue. There are many potential causes of cirrhosis, including NAFLD, AFLD, or a viral infection. If left untreated, cirrhosis can cause side effects like impaired liver function, portal hypertension, ascites (fluid accumulation in the abdomen), hepatic encephalopathy, and an increased risk of liver cancer.

How Can Pain Medications Harm the Liver?

Over the years, the U.S. Food and Drug Administration has approved many prescription and over-the-counter (OTC) medications for pain management. Since all of these medications work after entering the bloodstream, they all eventually pass through the liver. One of the biggest risks of such drugs is from their potentially toxic metabolites (byproducts). High doses of a common pain medication like acetaminophen, for instance, can lead to the accumulation of byproducts that can cause oxidative stress and liver damage. This can especially be a problem for people with chronic pain that have tried different combinations in an effort to find relief.

In most cases, though, pain relievers are well tolerated and don’t necessarily put the liver at risk through toxicity when used at the recommended dose. These medications are much more likely to exacerbate a liver injury or disease that’s already present. If someone already has liver cirrhosis, use of acetaminophen can lead to an elevation of certain liver enzymes that generally indicate hepatotoxicity and damage to the organ. Overall, however, this kind of risk can be mitigated by maintaining lower doses of acetaminophen.

Common Pain Relievers and Their Effect on Liver Health

As noted above, the dosage is a key factor in evaluating any pain relief medication (analgesic); selecting the right one will be based on the patient’s individual needs and instruction from a healthcare professional. Below are some examples of common pain relievers:

  • Acetaminophen: Also known as paracetamol, acetaminophen (Tylenol) is a medication used for the treatment of fever and mild pain. Though doctors are still not totally sure about the mechanism of action, it is believed to work by suppressing certain enzymes involved in the perception of pain. Acetaminophen has a slightly higher risk of liver damage because of a toxic metabolite called N-acetyl-p-benzoquinone imine (NAPQI) that can accumulate and cause oxidative stress.
  • Topical NSAIDs: Short for nonsteroidal anti-inflammatory drugs, NSAIDs work in a similar way as acetaminophen. While oral NSAIDs can have adverse effects on the liver, topical versions are valued for providing localized pain relief without significant systemic absorption.
  • Aspirin: Aspirin is a type of NSAID that is used for pain relief. It is generally well tolerated at moderate or low doses, but it also carries a higher risk of gastrointestinal bleeding or ulcers. It is less likely to harm the liver, however, because it forms non-toxic metabolites that are excreted in the urine.
  • Ibuprofen: Ibuprofen is another NSAID that is commonly used to relieve pain, reduce inflammation, and lower fever. In higher doses, it can also lead to accumulation in the liver and eventual damage.
  • Naproxen: Naproxen is also an NSAID, but it rarely harms the liver; in fact, it is regarded by some as the least likely to cause severe liver injury.
  • Opioids: Opioids are a controversial class of analgesics that are used for cases of moderate to severe pain, or when other pain relievers are not effective; examples include oxycodone and codeine. While opioids generally don’t directly cause liver damage, they can be the source of a number of other problems. Some opioids even contain other drugs like acetaminophen. Overall, these drugs should be treated with caution.

Ultimately, the best pain relievers will be specific to the individual and their particular health status. Over-the-counter options are usually safer, but even they can be overused or abused. Even if a drug doesn’t directly cause liver damage, there are other ways that overuse of painkillers can cause medical problems.

Cary Gastroenterology for Digestive Health

Everyone experiences pain from time to time, and there are many options for different people with different needs. Moreover, the choice of pain reliever is only one factor in maintaining the health of the liver. At Cary Gastro, we are dedicated to providing comprehensive digestive healthcare so that our patients can realize full health and wellbeing. If you have been experiencing gastrointestinal symptoms that you can’t explain, it may be time to see a gastroenterologist. Please contact our team today to request an appointment.