Non-steroidal anti-inflammatory drugs (NSAIDs) - which include ibuprofen and are used to relieve pain and fever - may also kill bacteria, a study found.
Research published in the Cell Press journal Chemistry and Biology suggests NSAIDs act on bacteria in a way that is fundamentally different from antibiotics.
Experts believe the discovery could eventually pave the way for new treatments to fight "superbugs" which are resistant to current antibiotics.
Dr Aaron Oakley, from the University of Wollongong in Australia, led the study on three NSAIDs: bromofenac, carprofen and vedaprofen.
He said: "We discovered that some anti-inflammatory drugs used in human and veterinary medicine have weak antibiotic activity and that they exert this secondary activity by preventing bacteria from copying their DNA, which they need to do in order to multiply.
"The fact that the bacteria-killing effect of the anti-inflammatory drugs is different from conventional drugs means that the NSAIDS could be developed into new kinds of antibiotics that are effective against so-called superbugs.
"This is important because the superbugs have become resistant to many - and in some cases most - of the available antibiotics."