NEW YORK: America's multibillion dollar pharmaceutical industry has been shaken by reports that Pfizer's high-profile arthritis drug, Celebrex, is said to cause an increased risk of heart attack.

Pfizer has decided to withdraw most of its print and television advertisement for the drug after growing complaints against the drug and renewed scrutiny by the Food and Drug Administration (FDA).

A new study showed that high doses of the drug had cardiovascular implications.

In what is considered one of the biggest ad budgets for a prescription drug, Pfizer mounted a $71 million advertising budget for marketing Celebrex earlier this year. The ad budget was spent over the last nine months.

However, the new study has stopped the company in its tracks even as the FDA might consider imposing severe label warnings and perhaps even withdraw it from the US market.

Earlier, another pain reliever, Vioxx, produced by Merck was withdrawn from the market after a study reported a tripling in the risk of heart attacks and strokes among patients using it for a long time.

The findings about Celebrex, made public on Dec 17, showed an increased risk of heart attack in patients taking either 400 milligrams or 800 mg of Celebrex daily. Most arthritis patients take 200 mg of Celebrex.

A statement on the FDA's website said: "The Food and Drug Administration (FDA) learned from the National Cancer Institute (NCI) and Pfizer, Inc. that NCI has stopped drug administration in an ongoing clinical trial investigating a new use of Celebrex (celecoxib) to prevent colon polyps because of an increased risk of cardiovascular (CV) events in patients taking Celebrex versus those taking a placebo."

Experts quoted by television networks say that in the face of pressure to produce more drugs quickly the FDA as well as the pharmaceutical industry could have rushed through some of the trials.

Pfizer, riding on the wave of enormous success with the erectile dysfunction medicine Viagra, had been aggressively marketing Celebrex.

However, last month the company was forced by the FDA to withdraw two television advertisements for overstating the effectiveness of Viagra.

Before the problems hit Celebrex sales, the company was expected to make $4 billion in its worldwide sales. They are now expected to slow down significantly.

Pfizer's chief executive, Henry A. McKinnell Jr., told "This Week," on ABC Television that the company had no plans to stop selling the drug. "We're leaving Celebrex on the market because it is an appropriate option for many, many patients," he said.

He company has maintained that the high heart risk was found only when patients took two to four times the usual dose.

Pharmaceutical companies such as Pfizer and Merck spend millions of dollars in research and trials for years before they win FDA approval. Experts said it was likely that financial pressures and market demands lead to some short cuts.