AstraZeneca and GSK shares rocked by safety concerns

More than £6bn was wiped off the value of the UK's two giant pharmaceuticals companies yesterday as they and the US regulator attempted to quell a furore over drug safety.

More than £6bn was wiped off the value of the UK's two giant pharmaceuticals companies yesterday as they and the US regulator attempted to quell a furore over drug safety.

One of the Food and Drug Administration's top safety officials listed GlaxoSmithKline and AstraZeneca products among five whose safety was questionable, but the FDA yesterday disowned his comments and insisted it had struck the right balance of benefits and risks by allowing the drugs on the market. AstraZeneca's shares fell 9 per cent to 2,145p as investors feared that many doctors may now stop prescribing Crestor, the new cholesterol-lowering drug that the company has promised will be a blockbuster. GlaxoSmithKline was 4 per cent lower at 1,147p, the next worst performer in the FTSE 100.

Both companies tried to play down the attack by David Graham, an FDA scientist, who highlighted the risks of five other drugs during a Senate hearing about Merck's withdrawal of its painkiller Vioxx in September. He also named Crestor, Serevent, one of GSK's asthma drugs, and Bextra, a painkiller made by Pfizer. He said their side effects needed more careful monitoring.

The drug companies argued yesterday that Mr Graham was a maverick within the FDA, a point of view supported by the agency's decision to publicly disown his opinions late yesterday. "Dr Graham's congressional testimony does not reflect the views of the agency. The five specific drugs that Dr Graham identified in his oral testimony are currently approved as safe and effective in the United States," the FDA said.

Sir Tom McKillop, AstraZeneca's chief executive, said he believed there would be little damage to Crestor sales as a result of Dr Graham's comments. "With the FDA having come out the way it has, I don't think it should have any enduring effects," he said, adding that there was no indication the FDA would review safety guidelines on Crestor, as the UK has asked European authorities to do. Sir Tom has promised Crestor will win 20 per cent of the global anti-cholesterol market, but sales have been disappointing because of a campaign by Public Citizen, a consumer group.

GSK's Serevent, which had sales of £264m in the first nine months of the year, has been on the market since 1990, but last year the FDA ordered a new warning be put on the label to show there have been a high number of asthma deaths among users. The FDA has been criticised over allegations it did not act more decisively against Merck, which recalled Vioxx after a trial showed it increased the risk of heart attacks in users. Mr Graham has been a critic of the drug for some time, and he has warned that due to inadequate controls by the FDA, the country was "virtually defenceless" against a repeat of the Vioxx debacle.

The FDA also fought back against accusations raised by Senator Charles Grassley, a Republican from Iowa, who said the FDA's relationship with drug makers was "too cosy".

Steven Galson, the acting director of the FDA's Centre for Drug Evaluation and Research, said the department which monitored drug safety had "strong support" within the organisation, and that it was independent from the office which reviewed applications for new drugs. "I think the drug industry would be astounded at the charges we're too cosy with them," he said in an interview with NBC's Today show.

Raymond Gilmartin, the chief executive of Merck, gave evidence at the Senate hearing, denying that the drugs giant dragged its heels in establishing the side effects of Vioxx and scrapping the drug.