NEW YORK (Reuters Health) - Drugmaker AstraZeneca, in a move seen as stifling Canadian Internet sales of prescription drugs to U.S. customers, intends to limit supplies of its products to Canadian pharmacies and wholesalers, a spokeswoman confirmed on Tuesday.

AstraZeneca becomes the second major pharmaceutical manufacturer, after GlaxoSmithKline, to take steps to cut supplies of its products to Canadian companies serving Americans.

In an April 8th letter to Canadian drug wholesalers and retailers, AstraZeneca said it was instituting an "allotment program" due to spikes in demand for several of its leading products.

Rachel Bloom-Baglin, a senior spokeswoman at AstraZeneca's U.S. headquarters in Wilmington, Delaware, said the firm received unusually large orders for the heartburn medications Nexium and Losec, which is sold as Prilosec in the U.S.

The heightened sales activity in recent months has "threatened our ability to ensure continued availability of those products to Canadian patients," she said.

"We're not cutting anybody off," Bloom-Baglin insisted. "We want to take a look based on historical purchasing patterns at what a customer has bought in the past."

All orders placed with AstraZeneca Canada will be reviewed and filled to the extent that the company can do so "without causing supply problems or backlogs elsewhere in the country," the letter indicated.

Glaxo, the world's second-largest drugmaker, said in January that it would stop supplying its drugs to Canadian Internet pharmacies that ship medicines to patients in America, sparking a backlash among some U.S. patient advocacy groups and politicians.

AstraZeneca is taking "a much softer approach, but the results could be the same," said Andy Troszok, vice president of standards at the Canadian International Pharmacy Association, which represents Internet pharmacies in Canada.

"We strongly feel that all of these moves are directly targeted at the international pharmacy business in Canada with the goal of stopping international free trade into the U.S.," he said.

Bloom-Baglin could not answer directly when asked whether AstraZeneca is seeking to squelch Canada's booming Internet pharmacy business.

"It's not a yes-or-no answer. The bottom line is we've got to manage the supply chain in Canada," she said.

"By the same token," she continued, "we are not going to condone activities that the FDA (Food and Drug Administration) has deemed illegal for the reimportation of drugs back into the United States."

AstraZeneca has told Canadian distributors that its allotment program will trigger audits for orders of Nexium and Losec, as well as the prostate cancer drug Casodex and the breast cancer treatment Arimidex, Troszok said.

Senior advocacy groups say AstraZeneca's move, like Glaxo's, removes another lifeline for older Americans for whom prescription medications are too expensive.

"Clearly, Canadian drugs are not the answer to this national emergency, but hundreds of thousands of Americans are able to afford medicines that doctors prescribe thanks to Canadian sales," said Robert Hayes, president of the Medicare Rights Center, a national consumer-advocacy group based in New York City.

Bloom-Baglin responded to critics by highlighting the company's investment in programs to help those who cannot afford prescription medicines. AstraZeneca provided the equivalent of $414 million in free or discounted drugs to more than one million patients in 2002 alone, she said.