PAINKILLERS LINKED TO GROWING ANTIBIOTIC RESISTANCE THREAT

The World Health Organisation already considers antimicrobial resistance a global health threat.

Ibuprofen and paracetamol might be the go-to medicines for headaches, fevers, or aches. Still, new Australian research shows they could be fuelling one of the most serious health crises of our time: antibiotic resistance.

A world-first study from the University of South Australia has found that these common painkillers not only contribute to antibiotic resistance when taken on their own but can actually amplify the effect when used together.

Researchers investigated the interaction between non-antibiotic medications, the antibiotic ciprofloxacin, and Escherichia coli (E. coli) – a bacterium responsible for causing gut and urinary tract infections.

They discovered that ibuprofen and paracetamol significantly increased bacterial mutations, making E. coli highly resistant to the antibiotic.

The findings have significant health implications, particularly in aged care facilities where residents are often prescribed a cocktail of medications.

The World Health Organisation already considers antimicrobial resistance a global health threat, noting it directly caused 1.27 million deaths worldwide in 2019.

Associate Professor Rietie Venter, who led the research, notes that the results highlight the hidden risks associated with polypharmacy.

“Antibiotics have long been vital in treating infectious diseases, but their widespread overuse and misuse have driven a global rise in antibiotic-resistant bacteria,” Assoc Prof Venter says.

“This is especially prevalent in residential aged care facilities, where older people are more likely to be prescribed multiple medications – not just antibiotics, but also drugs for pain, sleep, or blood pressure – making it an ideal breeding ground for gut bacteria to become resistant to antibiotics.”

When E. coli bacteria were exposed to ciprofloxacin in combination with ibuprofen and paracetamol, they developed more genetic mutations than when exposed to the antibiotic alone, allowing them to grow faster and establish multidrug resistance.

“We also uncovered the genetic mechanisms behind this resistance, with ibuprofen and paracetamol both activating the bacteria’s defences to expel antibiotics and render them less effective,” Assoc Prof Venter says.

The study examined nine medications commonly prescribed in aged care, including cholesterol-lowering drugs, blood pressure treatments, sleep aids, and decongestants. The results suggest antibiotic resistance is far more complex than previously thought, with everyday medicines playing a role.

“Antibiotic resistance isn’t just about antibiotics anymore,” Assoc Prof Venter says.

“This study is a clear reminder that we need to carefully consider the risks of using multiple medications – particularly in aged care, where residents are often prescribed a mix of long-term treatments.

"This doesn’t mean we should stop using these medications, but we do need to be more mindful about how they interact with antibiotics – and that includes looking beyond just two-drug combinations.”

The researchers are now calling for further investigation into drug interactions among individuals on long-term treatments to better understand how common medications may compromise the effectiveness of antibiotics.

The findings come as the University of South Australia and the University of Adelaide prepare to merge into the University of Adelaide in January 2026, combining their expertise to produce globally relevant health research on a larger scale.