Doctors should stop telling people to "complete the course" of some antibiotics, experts have warned.
Patients are put at unnecessary risk from antibiotic resistance when treatment is given for longer than necessary, according to an article in the British Medical Journal (BMJ).
Professor Martin Llewelyn at Brighton and Sussex Medical School and colleagues say the warning given to patients not to stop a course early is not supported by evidence and that research is needed to develop an alternative approach, such as stopping when you feel better.
They say such an approach would prevent the overuse of drugs, which can cause antibiotics to lose their effectiveness, meaning key medical procedures - including gut surgery, caesarean sections, joint replacements and chemotherapy - can become too dangerous to perform.
Current NHS and World Health Organisation (WHO) guidance says finishing a coursing of antibiotics is essential to prevent more virulent forms of disease.
But writing in the BMJ, the experts say the "complete the course" notion ignores the fact that different patients respond to treatments in different ways, adding: "Currently, we largely ignore this fact and instead make indication specific recommendations for antibiotic duration that are based on poor evidence.
"This situation is changing in hospital practice, where biomarkers of treatment response can guide when to stop antibiotic treatment.
"Outside hospital, where repeated testing may not be feasible, patients might be best advised to stop treatment when they feel better, in direct contradiction of WHO advice."
For common bacterial infections no evidence exists that stopping antibiotic treatment early increases a patient's risk of resistant infection, the experts said.
Reducing unnecessary antibiotic use is essential to mitigate antibiotic resistance, they argued, adding that antibiotics are a "precious and finite natural resource" which should be given to each patient with a tailored treatment duration.
They say research is needed to determine the most appropriate simple alternative messages, such as "stop when you feel better".
Commenting on the paper, spokesman for the Royal Pharmaceutical Society and consultant pharmacist Dr Kieran Hand, said: "Further research is needed before the 'finish the course' mantra for antibiotics is changed and any alternative message such as 'stop when you feel better' can be confidently advocated.
"The ideal future scenario would be that the right length of treatment for a specific infection for patients is identified from clinical trials and the exact quantity needed is prescribed and dispensed."