Bowing to pressure from lawmakers, Dr. Robert Califf, President Barack Obama's nominee to lead the Food and Drug Administration, said on Thursday the agency would reform its process for approving opioid painkillers.

Last month Democratic Senator Edward Markey of Massachusetts placed a hold on Califf's nomination, preventing it from being voted on by the full Senate, until the agency agreed to convene an advisory panel to review future opioid approval decisions.

The FDA said it agreed to convene a committee before approving any new opioid that does not have abuse-deterrent properties. And it said the agency's pediatric advisory committee will make recommendations before any new labeling relating to children is approved.

That was not enough for Markey, who said in a statement the FDA's actions "fall short of what is needed." He said the agency should convene an advisory committee meeting to inform all of its opioid approval decisions, not just for drugs that lack abuse-deterrent properties.

"Until the FDA commits to convene advisory committees of outside experts for all its opioid approval decisions, I will continue my hold on Dr. Califf's nomination," he said.

The FDA said in its announcement it would develop additional safety information for immediate-release opioid painkillers; strengthen the requirement for drugmakers to produce information after a drug reaches the market; and expand access to abuse-deterrent opioid drug formulations.

It is also considering making naloxone, a drug used to help people withdraw from opioids, accessible over the counter to treat opioid overdose.

Califf, who joined the FDA a year ago as a deputy commissioner, said that while the agency is not taking the action specifically in response to Senator Markey, it has heard what he and others in Congress had to say.

"That kind of pressure, when it's put on for general policy issues, helps us think," Califf said on a conference call with reporters.

Califf, a well-regarded cardiologist and researcher, said the agency's action should not be considered a precedent for others seeking to influence its drug approval policy.

"Under no circumstances can an FDA decision, particularly about a specific product, be subject to direct political pressure," he said, "but for broad FDA policies when we are in extraordinary circumstances we need to think differently, and we've taken that advice seriously."

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U.S. deaths from drug overdoses hit a record in 2014, increasing 6.5 percent to 47,055, propelled by prescription painkiller and heroin abuse, according to the U.S. Centers for Disease Control and Prevention.

In 2014 the FDA was forced to defend its decision to approve the powerful painkiller Zohydro, and last year the agency stirred controversy when it approved the use of the painkiller OxyContin for certain children suffering from cancer or other sources of severe pain.

Senator Bernie Sanders, a Democratic candidate for President, has also placed a hold on Califf's nomination, saying his extensive ties to the pharmaceutical industry "give me no reason to believe that he would make the FDA work for ordinary Americans, rather than just the CEOs of pharmaceutical companies."