One in four GPs have treated patients for adverse reactions to medicines bought online, according to a survey.

The poll of 483 GPs carried out by GP newspaper found that 25% reported treating patients for adverse reactions to drugs bought on the web and a further 8% said they may have done so.

Dr Bill Beeby, prescribing lead for the BMA’s GPs committee, told the paper he had concerns about online pharmacies being used for supply of medicines for conditions such as erectile dysfunction.

He added: “When it comes to buying drugs on the internet, it is a minefield. People just don’t know what they’d be getting. I wouldn’t advise any of my patients to go down that route.”

Dr Sarah Jarvis, a GP in west London and RCGP spokeswoman, said: “Surveys looking at many online medications suggest that the proportion of counterfeits is enormously high and that many of them contain very worrying ingredients.”

The results have led the Royal Pharmaceutical Society of Great Britain to urge patients to be aware of the risks when buying medicines over the internet, and to launch its own logo to try and promote safer purchasing.

David Pruce, director of policy for the RPSGB, said it had created the Internet Pharmacy Logo “to help the public identify bona fide pharmacy websites where they can purchase medicines safely.”

“We also advise members of the public to make other checks in addition to looking for the Internet Pharmacy Logo when buying medicines online,” he added.

“These include: checking the registration status of the pharmacist; looking for the name and address of the pharmacy operating the website, as it should be connected to a ‘bricks and mortar’ pharmacy; and avoiding websites offering to supply prescription-only medicines without a prescription.”

The RPSGB has also teamed up with the Medicine and Healthcare products Regulatory Agency (MHRA) to produce more than 600,000 leaflets on counterfeit medicines that community pharmacists will be asked to put in prescription bags from the end of this month.

The two-sided postcard gives patients advice on what counterfeit medicine is, how to minimise the risk of buying fakes and what patients should do if they think they have been sold counterfeits.

The leaflet targets specific products that have been previously counterfeited for UK sale including erectile dysfunction products, slimming medicines and products recalled since 2005.

Heidi Wright, the RPSGB’s head of practice, said: “We urge pharmacies to help us keep their patients informed of the safest way to obtain medicine by inserting this leaflet with certain patients’ prescriptions. The aim is to discourage people from buying medicines from an un-reputable source in future.”

Mick Deats, Group Manager of Enforcement the MHRA, added: “Our message is simple – do not buy prescription-only medicines over the internet without a prescription and if you are illegally selling or supplying medicines, we will use all appropriate measures at available to stop you, including prosecution and confiscation."