At a time when more people are looking to save money on prescription drugs, their exposure to counterfeit drugs is rising, says Pfizer's head of counterfeit intelligence.

Phony medicines are increasingly making it across U.S. borders, often via Internet sales, and creating a threat to consumer safety, says John Theriault, a former FBI agent who now serves as the vice president of global security for Pfizer Inc.

Occasionally, the phony medicines even make it into the legitimate sales stream.

"The Internet is pretty much an unregulated flea market," he said.

The safety of consumers is at risk as global drug counterfeiters become more sophisticated in the manufacturing and marketing of replicas of such blockbuster drugs as Viagra, Lipitor and Norvasc, Theriault said.

The World Health Organization estimates global sales of counterfeit medicines at $40 billion this year. The Center for Medicines in the Public Interest in New York predicts that counterfeit drug sales will reach $75 billion globally in 2010.

The reason for the projected increase in the United States: drug costs increasing by double-digits annually at a time when many Americans are becoming responsible for more of their own costs.

It makes for a tempting market for criminals who counterfeit drugs, Theriault said. It's forcing Pfizer to add to its global team of investigators. Currently, the world's largest drugmaker employs about 15 counterfeit investigators, but Theriault is in the process of adding a handful more in the booming counterfeit hubs of China and India.

The U.S. drug supply remains one of the safest in the world, Theriault said. Still, consumers must be vigilant as they shop for low-priced drugs, particularly on the Internet.

Counterfeit drugs are often sold by Web sites that claim to be legitimate pharmacies based in the United States or Canada, Theriault said. But the contents of the drugs vary. Some contain active ingredients, but others contain no active ingredient or even harmful ingredients.

"Congress always asks, 'If this is such a big problem, where are the bodies?' " Theriault said. "But if someone believes they are taking a heart medicine, but it has no active ingredient, we say that is a threat. We're trying to raise awareness so we don't see a lot of dead bodies."

Many times fake drugs look just like the authentic product. But sometimes there are subtle differences that consumers should be on the lookout for, Theriault said.

For example, the shape or color of a medicine may be just slightly different in a counterfeit, so patients should pay attention to make sure the pills all look the same, he said. Packaging colors or printing may differ slightly as well. Or the box may not contain patient safety information.

The message, Theriault said, is: "Know your medicine."

David MacKay, a consultant to Online Canadian Pharmacies, said consumers need to do their homework.

Customers should make sure any online pharmacy they plan to use requires a prescription and has a street address, he said. They should also verify an online pharmacy's license name and number with the state, province or country in which the pharmacy operates.

"There are licensed and legitimate Canadian pharmacies that provide perfectly safe medicines," MacKay said.

Occasionally phony drugs make it into mainstream U.S. and Canadian drugstores, but it's still rare, Theriault said.

Authorities uncovered a Lipitor ring in 2003 when a woman who had taken the cholesterol fighter for some time put a counterfeit pill in her mouth and noticed it began to dissolve before she could wash it down with water. She'd purchased it from her local pharmacy.

"She called her pharmacist and she called us," Theriault said. "That's the way we find most counterfeits, through customer complaints."