Over the past five years, more than 37 million doses of painkillers, antibiotics and other medicines have been given to someone in the UK for whom they were not prescribed, according to new research.

Heart medicines, statins, depressants and oral contraceptives are also among the prescription drugs which are being passed on by more than a million people every year, in the mistaken and dangerous belief that they are doing someone a favour, says the study, released by community pharmacy chain Lloyds Pharmacy.

With only half of all prescription medicines being taken as directed, it seems that there is no shortage of “spare” drugs available for amateur dispensing, comments the firm, which describes the trend as a “prescription for disaster.”

“You’d think that everyone instinctively understands the potential danger in giving a prescription medicine to a friend or relative, but according to our research more than 6.3 million people have done just that,” said Andy Murdock, pharmacy relations and governance director of Lloyds Pharmacy.

14% of 2,043 adults polled for the survey said they had given their prescription drugs to other people during the last five years, 16% of women and 10% of men acknowledging that they had done so. The practise is most prevalent among older patients and people on lower incomes, suggesting that prescription costs may be one of the factors at play. The survey also shows that one in four homes in the UK has some prescription medication which is no longer being taken, and in 2008 Lloyds also reported that there were 40 million items of out-of-date prescription medicines in Britain’s medicine cabinets.

“Doctors prescribe particular drugs to suit the individual needs and circumstances of the patient,” said Mr Murdock. “If you cross the wrong drug with the wrong person, the results could be awful, even fatal. What’s more, it’s likely that many of the drugs which are passed on are out-of-date, and that presents its own dangers.”

He acknowledged that people may think they’re being neighbourly by giving someone a prescription drug such as a painkiller. “You can understand the thought process; the drug has worked well for the patient, they have a friend who seems to be displaying similar symptoms and they have some pills to spare. It seems like a harmless and kind act to throw over a bottle and say, try one of these.”

“But they could be allergic to the active ingredient, or it may be contra-indicated with other medication they are taking. And of course, the ‘diagnosis’ may well have been wrong in the first place,” he says.

The trend was also condemned by Professor Steve Field, chairman of the Royal College of General Practitioners (RCGP), who was quoted by The Guardian newspaper as emphasizing that: “prescriptions are given out on trust between the GP and the patient. Drugs should never be shared on passed on to people they weren’t intended for. Patients should stop doing this.”