Older couple walking in a field holding handsShare on Pinterest
A new study found that acetaminophen changes proteins in the cardiovascular tissue, potentially affecting heart function. Maskot/Getty Images
  • Acetaminophen, commonly known as Tylenol, is a widely used OTC medication for mild to moderate pain.
  • Past studies show that in people with heart disease, acetaminophen is the preferred pain treatment over other types of pain medications like NSAIDs.
  • A new study using a mouse model discovered that acetaminophen changes proteins in the heart tissue, potentially affecting biochemical pathways needed for important functions.

Acetaminophen — the active ingredient in Tylenol — is a widely used over-the-counter (OTC) medication used for the treatment of mild to moderate pain, as well as for fever reduction.

Past studies show that in people with heart disease, acetaminophen is the preferred pain treatment over other types of pain medications like aspirin and ibuprofen, which are known as nonsteroidal anti-inflammatory drugs (NSAIDs).

A new study presented during the annual meeting of the American Physiological Society April 4–7 has discovered — using a mouse model — that acetaminophen changes proteins in the heart tissue.

These implications could potentially affect biochemical pathways needed for functions like energy production and antioxidant use.

For this study, researchers used a mouse model to study the effects of acetaminophen on heart tissue.

Some mice were given plain water, while others were administered water containing an amount of acetaminophen equivalent to 500 mg — the concentration found in one tablet of extra-strength Tylenol.

After seven days, researchers found significant changes in the heart tissue proteins of the mice given acetaminophen compared to the mice that only had water.

These protein alterations were associated with biochemical pathways responsible for many functions, including energy production, antioxidant usage, and the breakdown of damaged proteins.

The scientists found more than 20 different signaling pathways affected by the protein changes.

“We were surprised by the findings since we predicted that acetaminophen, when used at these concentrations, would have minimal effects on the heart,” Gabriela Del Toro Rivera, a doctoral student in the laboratory of Aldrin Gomes, PhD, at the University of California, Davis, and the first author of this study, told Medical News Today.

“While existing literature primarily associates acetaminophen overuse with liver damage, our research suggests that acetaminophen may influence tissues beyond the liver.”

Historically, acetaminophen has been the safest pain reliever for people with cardiovascular disease.

A study published in March 2015 found the use of acetaminophen was not linked to a higher risk of stroke, myocardial infarction, or any cardiovascular event.

Other recent studies have evaluated the safety of acetaminophen in people with heart disease.

Research published in 2022 found the use of sodium-containing acetaminophen as associated with increased risk for cardiovascular disease and all-cause mortality in people with or without high blood pressure.

Another 2022 study reported that regularly taking 4 grams of acetaminophen each day increased systolic blood pressure in people with high blood pressure, potentially increasing their heart disease risk.

“Since acetaminophen is one of the most commonly used over-the-counter drugs worldwide, gaining a better understanding of how acetaminophen may affect the heart is essential for improving patient safety, optimizing treatment decisions, managing comorbidities, and guiding future research and development efforts,” Del Toro Rivera said.

“Findings regarding acetaminophen’s effects on the heart have the potential to enhance doctor-patient communication by enabling more personalized recommendations, informed decision-making, and proactive management of potential risks associated with its use. Utilizing acetaminophen for the shortest duration and at the lowest effective dosage appropriate for an individual’s ailment is likely advisable.”

Gabriela Del Toro Rivera, first study author

While both acetaminophen and NSAIDs assist with pain relief, NSAIDs also help lower inflammation, which acetaminophen does not do.

Past studies show that NSAID use is associated with an increased risk for several cardiovascular concerns, including:

“Non-steroidal anti-inflammatory drugs, such as naproxen, ibuprofen, and diclofenac, are associated with an increased risk of stroke, and our research suggests that these commonly used drugs alter signaling pathways and cause mitochondrial dysfunction in mouse hearts,” Del Toro Rivera said.

“To determine if the anti-inflammatory properties of NSAIDs were responsible for the changes observed in mouse hearts from mice treated with NSAIDs, we investigated the impact of acetaminophen on proteins in heart tissue,” she continued.

“Since acetaminophen is commonly used and does not contain anti-inflammatory properties, the effects on the heart that would be observed would not be due to anti-inflammatory results.”

After reviewing this research, Cheng-Han Chen, MD, a board certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, told MNT he was surprised by the findings.

“We typically recommend acetaminophen as a medicine that people can take for pain that should not have any harm to the heart,” Chen explained.

“(With) NSAIDs, we do worry about its effects such as increased risk of clotting and increasing blood pressure. Typically, we recommend (that) our heart patients take acetaminophen instead since most of our studies show that it does not have a harmful effect on the heart. With so many patients taking acetaminophen, It would definitely be important to know whether it has effects that we don’t know about.”

— Cheng-Han Chen, MD, cardiologist

MNT spoke with Rigved Tadwalkar, MD, a board certified consultant cardiologist at Providence Saint John’s Health Center in Santa Monica, CA, about the study.

Tadwalkar said he was concerned and cautious about the implications of the study findings.

“The findings indicate that even at moderate doses considered safe for use, acetaminophen may have significant effects on signaling pathways within the heart tissue,” Tadwalkar said.

“This suggests that the commonly used painkiller might not be as benign as previously thought, especially when used regularly over time.”

“As a cardiologist, it is particularly troubling given that many of our patients rely on acetaminophen for pain relief, especially considering that other pain medications often pose significant risks,” he added. “Understanding the potential risks associated with acetaminophen use underscores the need for increased awareness, in order to make better decisions for patient care.”

— Rigved Tadwalkar, MD, cardiologist

Chen said the changes in how the heart responds to acetaminophen in mice show the heart was under more stress.

“It remains to be seen whether this also translates to humans,” Chen said. “This mouse research should lead to human studies, probably starting from observational studies, to investigate whether there are cardiac outcome effects from acetaminophen.”

Tadwalkar said the next steps for this research should involve further investigation into the mechanisms by which acetaminophen affects the heart and cardiovascular system and whether similar findings can be reproduced in humans.

“This should include studies in human subjects to determine if the findings observed in mice translate to humans,” Tadwalkar said.

“It would be valuable to explore whether there are certain subpopulations of patients who may be more susceptible to the cardiac effects of acetaminophen, such as those with preexisting cardiovascular conditions or other comorbidities,” he concluded.