Democratic U.S. Sen. Edward Markey of Massachusetts said on Monday he has placed a hold on President Barack Obama’s nominee to head the Food and Drug Administration until the agency agrees to reform its process for approving opioid painkillers.

Markey wants future opioid-approval matters to be reviewed by an FDA advisory committee, and believes the committee should consider the risk of addiction and abuse during the approval process. He also wants the agency to rescind approval of OxyContin for children and convene an advisory panel to guide that process.

“Last year, the FDA approved a new pediatric use for OxyContin without convening an advisory committee even though its guidelines note that FDA decisions that relate to controversial issues or matters relating to children are particularly well-suited to advisory committee empanelment,” Markey said in a statement.

The nominee, Dr. Robert Califf, a cardiologist and researcher, is widely expected to be approved when the Senate votes on the nomination later this year, though critics argue that his ties to the pharmaceutical industry are too close.

The FDA did not immediately have a comment on Markey’s action.

A “hold” is a procedure by which a senator can prevent a measure from being voted on by the full Senate.

The Senate Committee on Health, Education, Labor and Pensions voted earlier this month to confirm Califf as FDA commissioner, a position open since Dr. Margaret Hamburg stepped down last February.

Republican Sen. Lisa Murkowski of Alaska voted in favor of moving the nomination to the full Senate, but repeated a threat to oppose it if the FDA does not satisfy her demand for mandatory labeling of genetically engineered salmon.

Califf joined the FDA a year ago as a deputy commissioner. He is a prominent cardiologist who previously held senior positions at Duke University, where he founded a large academic research center that received more than half its funding from the drug industry.

He has also led multiple large-scale, company-funded clinical trials and published more than 1,200 papers. His interest in streamlining the clinical trial process dovetails with those of patient groups and members of Congress who are eager to see new drugs brought to market faster.

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 Centers for Disease Control and Prevention.

Drug overdoses are seen as a major contributor to recently rising death rates among middle-aged white Americans.

Since 2000, deaths from powerful, highly addictive opioids have jumped 200 percent, the CDC said, with those addicted to prescription painkillers, such as hydrocodone, increasingly turning to widely available, often cheaper heroin.