A review study led by the International Journal of Clinical Practice published in its March edition estimates global sales of counterfeit medicines are worth more than $75 billion, having doubled in just five years between 2005 and 2010.
Studies have identified large numbers of Web sites supplying prescription-only drugs without a prescription and people buying Internet drugs despite being aware of the dangers, the journal reported.
"Counterfeit medicines pose an every-increasing threat to public health, including death and inadequate healthcare as a result of self medication," Dr. Graham Jackson, the journal's editor and review leader, said.
"Particularly worrying examples include counterfeit cancer and heart drugs and fake vaccines sold during the bird and swine flu scares."
Counterfeit drugs are being found in legitimate supply chains, the review found.
For example, Britain has had nine product recalls in the last three years after counterfeit medicines reached pharmacy and patient levels, it said.
"It is vital that healthcare professionals play a proactive role in fighting the rise in counterfeit medicines by reporting all suspected cases to the relevant health authorities," Jackson said.