The US Food and Drug Administration yesterday asked Pfizer to withdraw its Bextra arthritis drug, saying the "overall risk versus benefit profile for the drug is unfavourable".

The FDA also requested Pfizer to include a heart-risk safety warning on its Celebrex drug and asked other makers of prescription anti-inflammatory pain drugs to include a similarly strong warning.

Bextra and Celebrex are among the class of drugs called cox-2 inhibitors which have raised concerns of increased heart and stroke risk.

The FDA said it would carefully review any proposal by Merck to resume sales of its Vioxx painkiller, also a cox-2 drug. Merck withdrew Vioxx in September because of safety concerns.

Shares in Pfizer, which employs around 1,000 staff in Dublin and Cork, slid 1.6 per cent to $26.43 in early trading in New York. Merck was down almost 1 per cent at $32.60.

The surprise decision on Bextra threatens Pfizer's upbeat three-year financial outlook presented to Wall Street on Tuesday.

The world's largest drug maker outlined $4 billion in cost cuts by 2008 to help offset numerous patent expiries. It estimated the cuts would boost 2006 earnings per share by 10 per cent over this year's expected disappointing performance and by another 10 per cent in 2007, when the company expected new products to hit their stride.

Part of Pfizer's plan was for renewed interest and sales in both cox-2 drugs in the second half of this year. The FDA said yesterday Pfizer had agreed to suspend sales and marketing of Bextra in the US, pending further discussions with the agency.

In February, the FDA's advisory committee said Bextra and Celebrex could stay on the market pending the decision, provided they carried strong warnings of increased heart and stroke risk. However, the FDA said yesterday the risks presented by Bextra outweighed the benefits.