Pfizer, which manufactures Viagra, analysed 2,383 suspected counterfeit samples forwarded to the company by law enforcement agencies between 2005 and 2009.

It found that that a Hungarian sample contained amphetamine, a UK sample contained caffeine and bulk lactose and that printer ink had been used to colour some samples blue. Other samples contained metronidazole, which can have significant adverse effects when combined with alcohol." 

And a study of 370 seized "Viagra" samples carried out by the Dutch National Institute for Public Health found that only 10 were genuine, with a range of other drugs present in the samples.

"As well as the risk posed by unknown ingredients, internet drugs circumvent traditional healthcare and this poses its own risks as underlying health conditions could go undiagnosed if people don't seek medical advice" says Dr Jackson. 

The World Health Organization states that counterfeit medicines are a threat to communities and must be stopped and there is a general consensus that steps need to be taken to tackle the problem.   

"However, obstacles to effective action include the lack of a clear worldwide consensus on what constitutes a counterfeit drug and the fact that activities that are illegal in one country may be legal in another" says Dr Jackson.

"In some cases producing counterfeit medicine can be ten times as profitable per kilogram as heroin, yet in the UK someone can face greater legal sanctions if they produce a counterfeit T-shirt.

"What is clear is that we need much greater public awareness of the risks of buying counterfeit drugs, as lives are at risk.

"It is essential that healthcare clinicians get that message across."

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