Ibuprofen and paracetamol promote antibiotic resistance, study finds

New research from the University of South Australia (Australia), published in npj Antimicrobials and Resistance, shows that drugs such as ibuprofen and paracetamol are silently fueling one of the world's biggest health threats: antibiotic resistance .

In the first study of its kind, researchers found that ibuprofen and acetaminophen not only promote antibiotic resistance when used separately, but also amplify it when used together.

When testing the interaction between non-antibiotic drugs, the broad-spectrum antibiotic ciprofloxacin, and Escherichia coli (E. coli), a common bacterium that causes intestinal and urinary tract infections, researchers found that ibuprofen and paracetamol significantly increased bacterial mutations, making the E. coli highly resistant to the antibiotic .

This is an important finding that has serious health implications, especially for people in nursing homes, where multiple medications are regularly administered.

The World Health Organization (WHO) reports that antimicrobial resistance is a global threat to public health and that antibiotic resistance was the direct cause of 1.27 million deaths worldwide in 2019.

Lead researcher Associate Professor Rietie Venter of UniSA says the findings raise important questions about the risks of polypharmacy in older adult care.

"Antibiotics have long been essential in the treatment of infectious diseases, but their widespread overuse and abuse have led to a global rise in antibiotic-resistant bacteria," says Associate Professor Venter.

"This is especially common in nursing homes, where older adults are more likely to be prescribed multiple medications—not just antibiotics, but also pain, sleep, and blood pressure medications—making them an ideal breeding ground for gut bacteria to develop antibiotic resistance," the researcher adds.

Along these lines, he explained that in this study they analyzed the effect of non-antibiotic drugs and ciprofloxacin, an antibiotic used to treat common skin, bowel, and urinary tract infections. "When bacteria were exposed to ciprofloxacin along with ibuprofen and paracetamol, they developed more genetic mutations than with the antibiotic alone, which helped them grow faster and become highly resistant. Worryingly, the bacteria were not only resistant to the antibiotic ciprofloxacin, but an increase in resistance to many other antibiotics from different classes was also observed," he explained.

"We also discovered the genetic mechanisms underlying this resistance, as both ibuprofen and paracetamol activate the bacteria's defenses to expel the antibiotics and make them less effective," he emphasized.

The study evaluated nine medications commonly used in nursing homes: ibuprofen (an anti-inflammatory pain reliever), diclofenac (an anti-inflammatory used to treat arthritis), acetaminophen (paracetamol for pain and fever), furosemide (for high blood pressure), metformin (for high blood sugar related to diabetes), atorvastatin (to help lower cholesterol and fats in the blood), tramadol (a stronger pain reliever used after surgery), temazepam (used to treat sleep problems), and pseudoephedrine (a decongestant).

Associate Professor Venter says the study shows that antibiotic resistance is a more complex challenge than previously thought, as common non-antibiotic medications also play a role. "Antibiotic resistance is no longer limited to antibiotics," he says.

"This study is a stark reminder that we must carefully consider the risks of using multiple medications, especially in the care of older adults, who are often prescribed a combination of long-term treatments," he said.

At this point, he clarified that this doesn't mean these medications should be stopped, but rather that we should be more aware of how they interact with antibiotics, and that includes looking beyond combinations of two medications.

Researchers are calling for more studies on drug interactions among people on long-term drug treatments so we can better understand how common medications can affect the effectiveness of antibiotics.