The US Food and Drug Administration, caught on the wrong foot again in just two years over the safety of the drugs it approves, is facing congressional investigations.
First it was Vioxx, the painkiller, then some antidepressants and most recently Avandia, the diabetes pill.
Concerns over that drug and others have led Republicans and Democrats in the House and the Senate to call for investigations.
The hearing next week may highlight the growing internal dissension between officials who approve drugs and those who track the safety of drugs after they have been approval. Tension between the groups has long been common, but in recent months it has erupted into sniping.
It all came into the open at an advisory committee hearing last month on whether to approve a new arthritis drug.
On one side was Dr. David Graham, author of an internal report that found that Avandia substantially increased the risks of heart attack, findings similar to the medical journal's report.
On the other, Dr. Robert J. Meyer, an office director in the drug review division, and his boss, Dr. John Jenkins, were in a group deciding against warning about the potential risks.
There was little chance that the advisory committee or the drug agency would approve the arthritis drug, Arcoxia, at the hearing.
Behind the scenes, agency officials were battling over Avandia. Dr. Graham told the committee that top agency officials had demanded an unreasonable level of certainty about a drug's risks before agreeing to warn the public.
"They assume it's safe," Dr. Graham said of the top officials' analyses of safety data. "Which is just looking at things all the way wrong."
Dr. Jenkins said Dr. Graham's "characterization of how we look at safety data is simply false."
"We make our best informed judgment about what the regulatory action should be," Dr. Jenkins added.
The fact remains though even during Avandia's original trials, overseen by GlaxoSmithKline, the drug's maker, patients taking the drug had more than twice the rate of ischemic heart disease as recipients of placebos.
The medical reviewer for the F.D.A. expressed concerns, but in a further analysis decided that it was less of a problem.
Congressional investigators said the safety group recommended months ago that the drug agency put its severest warning on Avandia. The review group, which holds sway, has not done so.
Senator Charles E. Grassley, Republican of Iowa, and others on Capitol Hill, say the rift between the approval office and the safety office means that the two must separate and that the safety group must have more power. Mr. Grassley proposed such a split in an amendment this month; it failed by one vote.
Top House staff members said the Avandia case had breathed new life into Mr. Grassley's proposal, because the House will soon debate changing the drug agency.
When Dr. Andrew C. von Eschenbach took over the FDA in 2005, he promised improvements, and agency officials said they would no longer be caught flatfooted on drug safety.
Now on the defensive, Dr. von Eschenbach said the agency had done its best in regard to Avandia. It intended to warn patients rapidly when it received information that a drug might be unsafe.
At the same time, he said, the agency had to find a way to ensure that patients did not overreact to uncertain safety problems.