CHICAGO — Consumers shopping for medications on the Internet often are getting convenience, a good price and the cloak of privacy, but they may not be getting the real thing.

A burgeoning multibillion-dollar industry of counterfeit drugs – ranging from AIDS and cancer medications to antidepressants and sexual enhancers – is keeping regulators busy and leaving the public vulnerable.

These medicines can deliver too little, too much or none of the active ingredient – or the wrong one – and sometimes are adulterated with dangerous chemicals or contaminated by unsanitary manufacturing or storage conditions.

The FDA in recent years has confiscated millions of dollars’ worth of counterfeit medicine. The agency, in partnership with international regulatory, customs and law enforcement agencies from 100 countries, shut down thousands of Internet pharmacies selling illegal drugs and seized about $10.5 million worth of pharmaceuticals during a weeklong crackdown on counterfeit and unapproved medications that launched in late September.

But such enforcement action isn’t nearly enough to stop the proliferation of phony medicine, FDA officials concede.

“This is a drop in the bucket,” said Ilisa Bernstein, director of the Office of Compliance in the FDA’s Center for Drug Evaluation and Research. “We may have some impact on these 4,100 websites, but they can pop up days or weeks later using another URL….”

It is illegal in the United States to sell medication without a valid prescription. All U.S. pharmacies, including those offering drugs online, must be licensed in the state where they are based or where they do business.

Foreign pharmacies can be licensed in the United States only if they follow all state and federal laws and they distribute only FDA-approved products. No foreign pharmacy has met those requirements.

Yet consumers can access tens of thousands of illegal online pharmacies, many of them based overseas. Buying drugs under these circumstances is illegal.

“It’s as if they are going to the corner and buying drugs from a drug dealer,” said Dr. Bryan Liang, director of the San Diego Center for Patient Safety at the University of California, San Diego, School of Medicine.

Bernstein said it’s impossible to know exactly how many people have died or been hurt by taking counterfeit drugs, although there have been highly publicized cases in the United States and overseas.

Experts say some of the illegal operations are based in the United States, often with an elaborate cast of participants who make, sell and distribute the drugs. Many of the drug ingredients come from overseas.

“Sometimes one criminal operation will make the packaging with our name brand on it,” said Jeannie Salo, director of Eli Lilly’s global anti-counterfeiting operations. “Another operation may make the ingredient, which is not the (real) thing. Another person might operate an Internet site.”

The appearance of fakes can be convincing, she said. “In some cases, you’d never know unless you tested it,” Salo said.

Hundreds of counterfeits

Last year, 532 different medicines were identified as having been counterfeited, said Tom Kubic, president of the Pharmaceutical Security Institute, a global network of security directors for pharmaceutical manufacturers.

The top three classes of drugs were genitourinary medications – for erectile dysfunction and incontinence, for example – anti-infective drugs, including antibiotics and medications to treat HIV-AIDS, and cardiovascular drugs, Kubic said.

Still, experts say consumers should be reassured that drugs bought in drugstores such as Walgreens and CVS are safe. Some industry experts say a national track-and-trace system would make it easier to confirm legitimate products and identify suspicious ones. Efforts are under way to introduce federal legislation.

Other efforts are aimed at making it harder for criminal online pharmacies to operate. Liang has researched online pharmacies and found that the vast majority are illegal.

“The best way to fix the problem is to make sales of prescription drugs online illegal, period, unless it is from a VIPPS-accredited pharmacy,” he said.

VIPPS stands for Verified Internet Pharmacy Practice Sites, which was created by the National Association of Boards of Pharmacy to help distinguish legal pharmacies from illegal ones. Legal businesses are encouraged to display a VIPPS seal on their sites.

For now, it’s buyer beware. If a deal seems too good to be true, it probably is, experts said. And anything suspicious should be reported immediately to authorities.

“It is important to make sure that consumers recognize that the U.S. drug supply chain is among the safest in the world, and we have laws and regulations in place to make sure we have that closed system,” the FDA’s Bernstein said. “But we still need to be vigilant.”