WASHINGTON - Novartis AG failed to give the government prompt, accurate reports about deaths of dogs treated with a painkiller in the same class of medicines now linked to heart problems in humans, U.S. regulators have charged in a letter.

The drug, Deramaxx, is a COX-2 inhibitor approved for relieving arthritis and post-surgical pain in dogs.

Similar drugs for people are under heavy scrutiny after studies associated them with heart attacks and strokes. One of the drugs, Merck & Co Inc.'s Vioxx, was pulled from the market because of safety risks.

Death has been reported "in rare situations" when dogs were treated with Deramaxx, according to the drug's label instructions.

The Food and Drug Administration, in a warning letter dated Nov. 29, said Novartis Animal Health Services should have forwarded complaints about deaths and health problems in dogs given Deramaxx within 15 working days, but in some cases delayed as long as 10 months. Some reports, including ones involving deaths, appeared to have incorrect dates, the FDA said.

"Novartis failed to submit timely and accurate information to the FDA regarding serious (adverse drug experiences) associated with the administration of its FDA-approved animal drug product Deramaxx... during its first year of marketing," the FDA said.

The company also failed to submit proper information about post-approval studies of Deramaxx, the FDA charged. The drug is known generically as deracoxib.

Novartis officials could not immediately be reached for comment.

The FDA sends dozens of warning letters per year. Most of the issues raised are resolved without further regulatory action, although the letters sometimes lead to tougher steps such as product seizures.

The warning letter to Novartis is posted on the FDA Web site at http:/www.fda.gov/foi/warning_letters/g5108d.pdf.