NEW YORK – Canadian Internet pharmacies are turning to Europe for supplies, as pharmaceutical companies are choking off prescription drugs sent north of the border to stop the flow of cheap medicines back to the United States.

In the last six weeks, several drug makers have increasingly cut supplies to Canada, creating drug shortages for Internet pharmacies. Pfizer Inc., for example, cut off two Canadian wholesalers in February for supplying drugs to companies that were exporting them. Pfizer later resumed shipments to both companies after they agreed to stop doing so.

Canadameds.com will start selling drugs from England on its Web site within the next week, and universaldrugstore.com plans to start selling medicines from Ireland within the next month.

Universaldrugstore.com has also found another possible supplier in New Zealand and plans to check its safety standards before offering its medicines to clients.

Crossborderpharmacy.com is negotiating with several pharmacies in England and hopes to announce an agreement in three weeks.

Europe, like Canada, has government price controls that keep prescription drug prices well below those in America. Drugs in Canada are up to 50 percent cheaper than they are in the United States.

“We have to stay a step ahead of the drug companies,” said Jeff Yhl, president of universaldrugstore.com. “We have to scour the world for safe supply for our customers.”

Canadian Internet pharmacies’ moves to expand their supplier base comes at a time when many cities, states and members of Congress are looking to importation as a way to curb spiraling drug costs.

Earlier this month, New Hampshire became the third state to offer residents a link to a Canadian pharmacy on its official Web site.

Meanwhile, Sen. Charles Grassley, R-Iowa, introduced legislation that would allow drugs to be imported from Canada initially and then other countries. The bill would punish companies that limit drug sales to Canada.

AARP, the lobbying group for older Americans, recently ran a television ad campaign that urged Congress to find ways to lower drug costs and noted importation was an option.

The pharmaceutical industry vehemently opposes importation. It is technically illegal for Americans to import drugs but regulators have turned a blind eye to individuals who do so, and have warned them about the potential dangers of buying medicines abroad.

Jeff Trewhitt, spokesman for the Pharmaceutical Research and Manufacturers of America, said importing drugs from Europe poses the same risks as buying them from Canada: They may be counterfeit or unsafe because of improper storage or labeling. Importing price controls means less money for research and development, he said.

Patients having difficulty paying for drugs should shop around or explore drug companies’ patient assistance programs, Trewhitt said.

Pfizer, Eli Lilly and Co. and AstraZeneca PLC have taken additional steps toward limiting supply to Canada recently. Lilly spokesman Ed Sagebiel wouldn’t comment on Canadian pharmacies adding to their suppliers but said his company cut supply to avoid aiding an illegal practice.

Drug company actions have taken a toll.

Yhl said it takes a week to get Pfizer’s pain reliever Celebrex and has suggested to patients they might want to ask their doctors about Vioxx, a rival drug made by Merck & Co.

The Pfizer drug Arthrotec also takes a week to secure, Yhl said. Canadameds.com said it takes three to five days to get many Pfizer drugs.