U.S., Canada reviewing Nexium, see no heart risk

Edward Jones analyst Linda Bannister said she was not expecting sales to decline significantly at this point.

"Whether or not it's a big blow for them is very dependent upon what we end up seeing as a result of this initial concern," she said, noting that Nexium accounted for about 20 percent of AstraZeneca's revenue last year.

AstraZeneca and Procter & Gamble Co., which sells over-the-counter Prilosec, said they agreed with the FDA.

"It is the view of AstraZeneca that the study results conclude that the products are not associated with an increased risk of cardiac events," a company statement said.

AstraZeneca submitted information on May 29 from two studies of patients with severe gastroesophageal reflux disease who were treated with either of the drugs or surgery, the FDA said. The Prilosec study lasted 14 years, and the Nexium study followed patients for five years.

The FDA said both studies may have been skewed, in part because surgical patients tended to be younger and less likely to have risk factors for heart problems.

Fourteen other studies of patients treated for up to two years did not suggest a higher risk of heart problems with Prilosec, the FDA said.

Nexium and Prilosec are proton pump inhibitors that reduce the amount of acid produced by the stomach. Both are sold by prescription to treat acid reflux and ulcers. Prilosec also is sold over the counter for frequent heartburn. Merck & Co Inc. shares profits from the drugs.

More than 1 billion patients have taken the drugs, AstraZeneca said. Prilosec is known generically as omeprazole and Nexium is known as esomeprazole.

Other proton pump inhibitors include Prevacid, sold by a joint venture of Abbott Laboratories Inc and Takeda Pharmaceutical Co Ltd, and Wyeth's Protonix.