People who buy prescription medications over the Internet, especially drugs purporting to treat erectile dysfunction, are playing Russian roulette with their lives, a new study contends.

At best the drugs won't help you and at worst they could kill you, the review article said.

"You may be wasting your money or you may actually be hurting yourself," said Dr. Margaret E. Wierman, professor of medicine at the University of Colorado at Denver and chief of endocrinology at the Denver VA Medical Center, who was not involved with the study.

Counterfeit Internet drugs are a mushrooming problem. Seizures of fake drugs in Europe quadrupled between 2005 and 2007. And the number of investigations undertaken by the U.S. Food and Drug Administration increased by a factor of eight between 2000 and 2006, according to the study, published in the International Journal of Clinical Practice.

The sale of counterfeit drugs has almost doubled in the last five years, and will hit $75 billion in 2010, according to one estimate, making it one of the more lucrative illicit drug markets.

As many as 2.5 million men in Europe may have taken counterfeit sildenafil (Viagra), the study authors stated.

"It's a very significant problem and I think there are people who are being injured," said Dr. Ira D. Sharlip, a spokesman for the American Urological Association and clinical professor of urology at the University of California, San Francisco. "The only way to avoid the problem is not to buy on the Internet."

Viagra-like tablets bought on the Internet aren't necessarily any cheaper than the real thing, but they do allow buyers to avoid the shame factor often associated with asking for this type of drug.

"The motivation is the anonymity of buying drugs on the Internet. It's embarrassing to some men to go to a pharmacy and pick up his Viagra prescription, and it's also embarrassing for some men to go to a doctor and say, 'I have erectile dysfunction. I need some Viagra,'" Sharlip said.

The problem of fake drugs isn't limited to impotence treatments. According to the study, two pregnant women died after they were given injections of a counterfeit iron preparation for anemia, and 51 children died in Bangladesh of kidney failure after taking paracetamol syrup that was contaminated with diethylene glycol, which is often used as antifreeze in cars.

So many things can go wrong with Internet purchases.

"The purity of the medication or the quality of the medication is under no sort of scrutiny or any type of oversight to determine if, first of all, it is the correct medication. And second, if it is correct is it in the correct dosage?" said Dr. Michael Chehval, chief of urology at St. Louis University.

Study author Dr. Graham Jackson, a cardiologist at London Bridge Hospital in the United Kingdom, said: "The first danger is people don't know what's in it. Some are just talcum powder or brick dust, while some have a bit of Viagra or Cialis and some chemicals that have nothing to do with it. One batch actually contained amphetamine, which is an addictive drug. Tablets are made shiny with road paint or shoe polish. The content of the medication could be anything."

In 2008, four men in Singapore died after ingesting counterfeit impotence drugs that had been contaminated with a blood-sugar-lowering agent, the study reported.

And bypassing the involvement of a competent doctor means red flags could be missed.

"Erection problems can be an early warning sign of heart disease or diabetes," Jackson said. "If you do have a problem and don't see a doctor, diagnosis of those important conditions can be missed. Men with no symptoms at all who get an erection problem usually are an average of three to five years away from a heart attack. Instead of going to the Internet, they should be going to their doctors to find out if they are at risk and to do something about it."

Problems also can occur when the impotence drugs actually do contain phosphodiesterase type 5 inhibitors (PDE5), the main ingredient in Viagra, as well as vardenafil (Levitra) and tadalafil (Cialis).

"People with underlying heart problems are at risk for cardiac events if they take this class of medication," Chehval said.

According to the review article, about one-third of men reported sidestepping a health-care professional when buying erectile dysfunction drugs.

"This is a really serious issue. We can fix the erectile dysfunction and we can also fix the chances of getting a heart attack," Jackson said.

Jackson is editor of the journal and reported multiple ties to pharmaceutical companies, including Pfizer, which makes Viagra. The review article covered more than fifty studies published between 1995 and 2009 and was conducted by British, Swedish and American researchers.