US health regulators lack the resources to monitor the safety of new drugs, a former head of the Food and Drug Administration warned this week.
FT.com reports that David Kessler, commissioner of the FDA from 1990-1997, believes the biggest threat to public confidence in drug safety comes from the widespread use of new medicines within weeks of their launch before a fuller picture of their potential side-effects is available.
Kessler also claimed that the agency had become more conservative in some circumstances in its attitude to new drugs.
"My greatest fear is the lack of post-marketing surveillance," he told the Financial Times. "It is often not until a drug is in widespread use that you can see if there are life-threatening events." European regulators faced the same problem, he added.
With some drugs, potentially lethal side-effects could occur in just one in every 20,000 patients, yet the clinical tests on the drug before approval might have involved only 5,000 people.
Partly as a result of lobbying by the pharmaceuticals industry, he said, the FDA had not been given the resources to keep a close eye on drugs after they were launched. However, as a result of aggressive marketing by companies, new drugs were often widely used shortly after their launch.
"This is a big fear because problems with products in the market can undermine efforts to have an effective drug review system," said Dr Kessler, who became a well known public figure through his strong support for tougher tobacco regulation.
The FDA, which is lobbying Congress to renew its funding, has come under fire in recent years because of a series of product withdrawals on safety grounds. Last year Lipobay, a cholesterol-lowering treatment, was pulled after it had been linked with 30 deaths - the figure has since risen to more than 100.
Dr Kessler, now dean of Yale University School of Medicine, said the FDA had become more "conservative" in some circumstances - an accusation levelled at the agency by many industry executives in recent years.
In the case of a drug for a chronic condition that was potentially toxic if used for more than a month, he said that in the past the agency might have approved it with a label recommending use for only a short period. However, now it would be more likely to reject the drug.
"The agency has learnt from past withdrawals and is more conservative in some cases, but this is not an across-the-board slowdown," said Dr Kessler.