Painkillers Damage the Liver and Kidney: How to Take Them Safely

Tylenol tablets, which contain acetaminophen, are shown on April 14, 2015 in Chicago, Illinois. Scott Olson/Getty Images

Pain relievers are convenient medications that can relieve pain in the body. Whether it is headache, fever, muscle pain, stomach pain, or period pain, people are used to taking pain relievers to stop the pain.

However, as long as the drugs are metabolized by the liver and kidneys, the liver and kidneys are vulnerable to damage if painkillers are not taken properly.

The over-the-counter pain medications that people can buy at pharmacies can be divided into two categories: Acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs). These two types of drugs have hepatotoxicity (harm to the liver) and nephrotoxicity (harm to the kidney) respectively.

1. Acetaminophen

The effect of Acetaminophen is only to relieve pain and reduce fever. It does not have any anti-inflammatory effect. Common pain relievers containing acetaminophen include Panadol and Tylenol.

Acetaminophen is hepatotoxic, as more than 90 percent of its metabolism is done in the liver. The impact of the drug is thus more on the liver than on the kidney.

However, according to pharmacist Chen Chia-Ling of Kuo General Hospital, Taiwan, the liver will be damaged only if the dose is too high. Acetaminophen can be metabolized from the body within 24 hours. If you take it according to the prescribed dosage, there will be no problem with accumulating toxins and liver damage.

The maximum dose of acetaminophen for adults is 4 grams per day, and one painkiller contains 500 mg, so one should not exceed 8 pills per day.

2. Non-steroidal anti-inflammatory drugs (NSAIDs)

NSAIDs are a class of drugs that contain a variety of medications, such as aspirin and ibuprofen. In addition to relieving pain and reducing fever, they also have anti-inflammatory effects and can be used for toothaches and gout. It can also reduce swelling and pain caused by arthritis or muscle sprains and strains.

NSAIDs are more likely to cause gastrointestinal discomfort and have a direct effect on the kidneys. Chen Chia-Ling explained that these drugs will reduce the blood flow to the kidneys when they are in action, causing a decrease in the glomerular filtration rate in the kidneys. This affects the kidney’s production of urine, resulting in water retention, low blood sodium, high blood potassium, high blood pressure, and even deterioration of kidney function. ^[1]

However, for people with normal kidney function, it will have little impact to take NSAIDs, which are safe for most people if used at the prescribed dose for a short period of time (less than 10 days). ^[2]

In addition to over-the-counter pain relievers, there are the most potent of prescription drug painkillers—opioids. These drugs contain morphine and are primarily intended for cancer patients or those with severe postoperative pain. The liver and kidneys are involved in the metabolism of opiate pain relievers, but at normal doses, there is no serious toxicity.

4 Mistakes When Taking Pain Relievers

Taking too high a dose is the most important reason why pain relievers cause harm. Dr. Chen recalls that one Valentine’s Day, a young man who tried to commit suicide was brought to the hospital after swallowing dozens of potent Panadol, causing acute liver damage. Fortunately, there is a special antidote for Panadol.

However, this is only a rare and extreme example. More often, people unknowingly take too many pain relievers.

• Common Scenario 1: Taking a medication according to a doctor’s orders, but taking too high a dose

Pain relievers can be used when the body has aches, pains, fevers, etc. Therefore, prescriptions containing pain relievers may be prescribed by family doctors, gastroenterologists, dentists, orthopedics, physical therapists, etc.

Chen Chia-Ling gave an example to show how overdose is possible: A patient may take the medicine prescribed by his orthopedic surgeon in the morning because of bone pain, and then goes to another clinic in the afternoon with a cold and fever and leaves with some cold medicine. Both of these drugs contain acetaminophen, and so the patient thus takes the medication in accordance with the doctors’ instructions, but the amount of painkillers they’ve taken in total is now too high in terms of toxicity.

In addition, judging only from the appearance of the pills, people usually don’t recognize them to be the same drug, which can be produced by different pharmaceutical companies after its patent expires and can look different—it may be white oval or yellow round and flat.

Therefore, when patients go to see a doctor or pick up medication, they should inquire with the doctors and pharmacists whether these drugs contain painkillers, because patients can see on a prescription whether there is Acetaminophen, but NSAIDs have many drug names that most of us can’t recognize at a glance.

• Common Scenario 2: Using pain relievers in combination with other medications

Another common scenario is that patients don’t know they are taking compound medicines that already contain pain relievers, and then take additional pain medication on top of that.

Compound medicine contains more than one ingredient. For example, a muscle relaxant with acetaminophen is used to reduce muscle soreness after exercise. Cold remedies include acetaminophen to relieve fever and pain, as well as cough suppressants to treat the symptoms of the common cold.

If people drink cold drops after catching a cold, and at the same time take pain relievers because of headaches, they will end up taking a double dose of painkillers. Dr. Chen said that over the course of a day, these doses end up exceeding your one-day safety limit.

In addition, some drugs are mixed with low doses of NSAIDs, such as aspirin, to boost the anti-inflammatory and pain-relieving effects. Therefore, patients with kidney problems should inform their pharmacists in advance, to avoid taking too many NSAIDs, which affect the kidney.

• Common Scenario 3: Taking pain relievers and putting on pain relief patches at the same time

The effect of a pain relief patch lasts about four to six hours, so if you use two or three patches a day, it’s the same as taking two or three doses of painkillers already. So if you take pain relievers three times a day as well, you'll have doubled the dose and burden on your body.

Dr. Chen stressed the importance of vigilance when it comes to combining medications. If you are already using pain relief therapeutics, you'll want to let your doctor know when they’re prescribing you painkillers.

• Common situation 4: Buying and taking drugs from unknown sources

Dr. Chen once met an elderly man in the hospital who showed her a rare, thousand-year-old herb he was taking as a pain reliever. The box had a sticker that read “Millennium Polygonum multiflorum,” but the fine print revealed that the ingredients consisted of a common painkiller, and Dr. Chen had to be the one to break the news to the unfortunate man that he had been duped into paying a lot of money for what essentially amounted to over-the-counter medication. To make matters worse, he was taking what he thought was an herb four times a day while also taking his prescribed painkillers, effectively putting himself at risk with this high total dosage.

There are a myriad of herbal remedies and supplements on the market, sometimes with branding that obscures their true ingredient makeup or source. Make sure to figure out what you are really taking, or don’t take it at all.

As different pain relievers have either hepatotoxicity or nephrotoxicity, some people should be especially careful when taking pain relievers.

So how should patients with liver or kidney issues take painkillers?

2 Types of Patients Should Be Careful With Acetaminophen

According to Wu Wen-Chieh, director of the Hepatobiliary and Gastroenterology Department of Taiwan’s Yuan-Rung Hospital, there are two types of people who should pay attention to acetaminophen pain relievers.

• Patients with alcoholic hepatitis and alcoholic cirrhosis caused by long-term alcohol abuse
• People who suffer from muscle deficiency and malnutrition due to cancer, anorexia, and other causes

These people are deficient in glutathione (GSH), an antioxidant substance found in the liver.

Only 5 percent of the metabolites of acetaminophen are hepatotoxic. Acetaminophen combines with glutathione in the liver to form a non-toxic compound, which is then eliminated from the body and will not harm the body. If you are deficient in glutathione, toxicity builds up and necrosis of liver cells occurs.

Therefore, when taking acetaminophen, these patients should pay special attention to the dosage, which should be limited to 2 grams a day, with a maximum of four capsules.

Patients with other liver diseases, such as viral hepatitis and nonalcoholic fatty liver disease (NAFLD) can take acetaminophen normally. Patients with severe cirrhosis of the liver caused by viral hepatitis should be careful when taking acetaminophen.

4 Types of Patients Should be Careful With NSAIDs

All NSAIDs have nephrotoxicity and increase the risk of gastrointestinal bleeding, myocardial infarction, and stroke. Therefore, the National Institute for Health and Care Excellence (NICE) defines the following people as high-risk patients: ^[3]

• patients aged >65 years
• patients using interacting medications
• patients with diabetes, hypertension, cardiovascular disease, or renal or liver impairment
• patients with a history of peptic ulcer or GI bleeding

The chief of the Department of Toxicology at Taiwan’s Lin Kou Chang Gung Memorial Hospital, Yen Tsung-Hai, added that diabetic patients are prone to nephropathy. He said that if diabetic patients and patients with chronic kidney disease take such pain relievers, their kidneys will deteriorate faster. He suggests that these patients take acetaminophen instead.

Acetaminophen is a Safer Choice for Patients With Both Liver and Kidney Diseases

Wu Wen-Chieh said that, compared with other pain relievers, acetaminophen is still a safer choice for patients with both liver and kidney diseases.

He explained that acetaminophen will hurt the liver only if 4 pills or more of them are taken a day. High-risk patients can take them if they control the dosage. For patients who have to use NSAIDs, he suggests that they should use the minimum dosage to reduce kidney damage and take the medicines after meals to reduce the risk of gastrointestinal bleeding.

Morphine-like drugs for patients with poor liver and kidney may trigger liver and brain lesions, causing neurological disorders in the brain, and should be used with caution, Wu added.

3 Red Flag Symptoms and Things to Look Out For

Chen Chia-Ling reminds patients not to buy pain relievers indiscriminately, not to take too many of them, and not to use them in combination. When using painkillers, patients should not drink alcohol, to avoid increasing the burden on their liver.

When using NSAIDs for relieving pain, patients should also avoid fasting to reduce the occurrence of gastrointestinal discomfort or gastrointestinal bleeding.

She added that contrast agents will be used during examinations, such as computed tomography, ultrasound imaging, and magnetic resonance imaging, which are not good for the kidneys. If these types of examinations are while the patient is on painkillers, it increases the risk of damage done to the kidneys.

When the following symptoms occur, they’re generally red-flag signs that one is taking pain medication the wrong way:

1. Poor mental performance, decreased activity, and loss of appetite: These may be due to liver problems caused by excessive acetaminophen.
2. Edema: If edema (swelling) occurs while taking NSAIDs for pain, where the patient previously had no edema, it is possible that the glomerular filtration rate has decreased and that water is not metabolized.
3. Stomach pain: Taking too many pain relievers can cause stomach damage, especially with NSAIDs, which can lead to gastrointestinal symptoms such as stomach aches, indigestion, and diarrhea. ^[4]

Many people are accustomed to relying on painkillers, but they ignore the root cause of their pain. If those symptoms still recur after taking painkillers, it is recommended to find out the cause of the pain.