Interpol said Thursday that police had seized nearly 10 million units of fake medicines worth $41 million (31 million euros) in a week-long operation carried out across 99 countries.
"The quantities seized increased by more than 100 percent against the preceding operation last year," said Aline Plancon from Ingterpol's department charged with tackling pharmaceutical fraud.
More than 9,000 Internet sites selling fake medicines were closed down during the "Pangea 6" operation, which began on June 18, and 58 people were arrested, she said.
According to the World Health Organisation, more than 50 percent of medicines bought online have been found to be fake.
Counterfeit cough syrup and other medicines laced with diethylene glycol have caused eight mass poisonings around the world, including in 2006 in Panama where more than 100 people died, many of them children, an Interpol statement said.
Coordinated by Interpol, the annual Pangea operation brings together customs, health regulators, national police and the private sector from countries around the world. It was launched in 2008.