Acetaminophen, also known as paracetamol in many countries, is one of the most widely used pain and fever medicines in the world. People often take it at home to ease headaches, muscle pain, or cold symptoms, and it is generally considered safe when used at the recommended dose.
Most of the time it is swallowed as a tablet or liquid, and the body processes it through the digestive system and liver before it enters the bloodstream. Because of its long record of safe use, many people think of it as a simple and gentle medicine.
In hospitals, however, doctors sometimes use a different method to give acetaminophen. Instead of a pill, they deliver it directly into a vein through an intravenous line, often called an IV.
This approach allows the medicine to work more quickly and is especially useful for patients who cannot swallow, are unconscious, or need rapid pain relief after surgery or injury. It also helps doctors control the exact amount of medicine a patient receives.
A new study has found that giving acetaminophen through an IV may cause an unexpected drop in blood pressure. Blood pressure is the force of blood pushing against the walls of blood vessels, and it must stay within a healthy range to ensure that organs receive enough oxygen and nutrients.
When blood pressure falls too low, patients may feel dizzy, weak, or faint, and in severe cases it can be dangerous.
Researchers led by Thomas Qvistgaard Jepps at the University of Copenhagen investigated why this drop happens. Their findings were published in the journal Atherosclerosis, Thrombosis, and Vascular Biology.
They observed that a significant number of seriously ill patients experienced lower blood pressure after receiving IV acetaminophen, and some required medical treatment to stabilize their condition. Surprisingly, the effect was not limited to the sickest patients and could occur in a wide range of people.
The scientists believe the reason lies in how the body handles the medicine when it bypasses the digestive system. When acetaminophen is taken by mouth, it passes through the liver first, where it is partly processed. With IV delivery, the drug enters the bloodstream directly and spreads throughout the body immediately.
This difference appears to affect potassium channels, tiny structures in the walls of blood vessels that help control how wide or narrow the vessels become. When these channels are activated, blood vessels relax and expand, which can lower blood pressure.
In experiments with rats, the researchers found that blocking these potassium channels prevented the drop in blood pressure. This discovery may lead to new strategies to protect patients who need IV pain relief, especially during emergencies or major illnesses when careful blood pressure control is critical.
For people taking acetaminophen at home in pill form, there is no need for concern, as the usual method of use does not appear to cause this effect. The findings mainly apply to hospital settings where IV treatment is used. Doctors and nurses can reduce risks by monitoring patients closely and responding quickly if blood pressure changes.
This research highlights an important lesson in medicine: the way a drug is given can change how it affects the body. Even well-known medicines can behave differently when delivered through another route. Understanding these differences helps healthcare professionals provide safer care and improves treatment decisions.
Scientists continue to study how common drugs interact with the body in different situations. Their work shows that careful research can uncover hidden effects and lead to better protection for patients. As medical knowledge grows, even everyday medicines can be used more wisely and safely.
If you care about high blood pressure, please read studies that early time-restricted eating could help improve blood pressure, and natural coconut sugar could help reduce blood pressure and artery stiffness.
For more information about blood pressure, please see recent studies about How to eat your way to healthy blood pressure and results showing that Modified traditional Chinese cuisine can lower blood pressure.
Copyright © 2026 Knowridge Science Report. All rights reserved.
