Common painkillers like ibuprofen and acetaminophen may fuel antibiotic resistance, raising urgent questions about drug interactions in aged care and beyond.
Ibuprofen and acetaminophen (paracetamol) are among the most widely used pain and fever remedies, but new findings from the University of South Australia suggest they may be contributing to a global health crisis: antibiotic resistance.
In a pioneering study, scientists discovered that each drug on its own can encourage bacteria to become resistant to antibiotics, and when taken together, they appear to intensify this effect.
By examining how these medicines interact with the common antibiotic ciprofloxacin and Escherichia coli (E. coli) – a bacterium often responsible for gut and urinary tract infections – the team observed that ibuprofen and acetaminophen accelerated genetic changes, making the bacteria more resistant not only to ciprofloxacin but also to other types of antibiotics.
According to the researchers, this raises significant concerns for vulnerable groups, especially older adults in residential care facilities where multiple medications are commonly prescribed. The findings highlight the need for greater caution around everyday drug use and its potential role in worsening antibiotic resistance.
The World Health Organization reports that antimicrobial resistance is a global threat to public health, and that bacterial resistance was directly responsible for 1.27 million global deaths in 2019.
Ibuprofen and acetaminophen are two of the most widely used over-the-counter pain relievers. Ibuprofen, sold under brand names like Advil and Motrin, is a nonsteroidal anti-inflammatory drug (NSAID) that reduces pain, fever, and inflammation. Acetaminophen, best known by the brand name Tylenol, is commonly used to relieve pain and reduce fever but does not have anti-inflammatory effects. Both are staples in household medicine cabinets and are often considered go-to remedies for headaches, colds, and everyday aches.
Polypharmacy and Its Consequences
Lead researcher UniSA’s Associate Professor Rietie Venter says the findings raise important questions about the risks of polypharmacy in aged care.
“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.
“In this study, we looked at the effect of non-antibiotic medicines and ciprofloxacin, an antibiotic which is used to treat common skin, gut, or urinary tract infections.
“When bacteria were exposed to ciprofloxacin alongside ibuprofen and paracetamol, they developed more genetic mutations than with the antibiotic alone, helping them grow faster and become highly resistant. Worryingly, the bacteria were not only resistant to the antibiotic ciprofloxacin, but increased resistance was also observed to multiple other antibiotics from different classes.
“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.”
Broader Medication Review
The study assessed nine medications commonly used in residential aged care: ibuprofen (an anti-inflammatory pain relief), diclofenac (an anti-inflammatory to treat arthritis), acetaminophen (paracetamol for pain and fever), furosemide (for high blood pressure), metformin (for high sugar levels linked to Diabetes), atorvastatin (to help lower cholesterol and fats in the blood), tramadol (a stronger pain medication post-surgery), temazepam (used to treat sleeping problems), and pseudoephedrine (a decongestant).
Assoc Prof Venter says the study shows how antibiotic resistance is a more complex challenge than previously understood, with common non-antibiotic medications also 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 calling for further studies into drug interactions among anyone on long-term medication treatment regimes so we can gain a greater awareness of how common medications may impact antibiotic effectiveness.
Reference: “The effect of commonly used non-antibiotic medications on antimicrobial resistance development in Escherichia coli” by Hanbiao Chen, Sylvia A. Sapula, John Turnidge and Henrietta Venter, 25 August 2025, npj Antimicrobials and Resistance.
DOI: 10.1038/s44259-025-00144-w
Funding: Medical Research Foundation
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