People who buy prescription medicine on the Internet risk taking drugs without proper instructions or even getting counterfeits, according to a new U.S. government report.

Drugs from Web sites in foreign countries were especially likely to be mishandled and exclude warning information, said the report released on Thursday by the General Accounting Office, the investigative arm of Congress.

Buying drugs online, especially from Canada, has become a growing trend as drug costs rise and more Americans lose health insurance benefits.

GAO officials bought samples of 11 medicines from 68 Web sites based in the United States, Canada, Argentina, India, Turkey and seven other countries.

The type of pharmacies varied but included some linked with well-known drugstore chains and some certified by industry groups.

“The availability and ease with which the drugs could be purchased varied by type,” the report said. While popular drugs were abundant, narcotic painkillers and other drugs with special restrictions were more difficult to obtain, it said.

Drugs sampled included Pfizer’s Lipitor, Zoloft and Viagra. Amgen’s Epogen and Abbott’s Vicodin were also among those sampled.

Foreign Internet pharmacies were more likely to ship packages without proper labels or packaging, GAO officials found. Four sent counterfeit medicines.

All 18 Canadian sites and five U.S.-based ones required prescriptions from the patient, but the other 24 U.S. and 21 foreign sites did not, the report said.

Overall, U.S. and Canadian-based sites posed “fewer problems,” according to the GAO.

Congressional legislation aimed at allowing safe imports of cheaper drugs from Canada or other countries includes provisions cracking down on unscrupulous Web pharmacies. The Senate may debate those bills this summer.

U.S. Food and Drug Administration officials agreed with most of the report, but argued it was impossible to prove where Web sites were based or where their products originated. “It is easy to design a fraudulent Canadian Web site that looks completely legitimate,” FDA officials wrote to the GAO.

The FDA has long opposed drug importation, saying it does not have the legal authority or resources to inspect imported medicine.