The Senate overwhelmingly confirmed President Barack Obama's nominee to be commissioner of the Food and Drug Administration on Wednesday despite frustration over the agency's response to the epidemic of painkiller abuse.

The vote was 89-4 for Dr. Robert Califf, a prominent cardiologist and medical researcher at Duke University for more than 30 years and the FDA's No. 2 official.

With only a year left in Obama's presidency, Califf will be tasked with wrapping up many of the administration's initiatives at the agency, including unfinished tobacco regulations and food safety and labeling reforms. He is expected to follow through on his pledge to re-evaluate how the agency regulates prescription painkillers like OxyContin.

"If addiction to opioids and misuse of opioids is the enemy, then we underestimated the tenacity of the enemy," said Califf, in an interview with The Associated Press. "We've got to adjust."

Under pressure from the Senate, Califf said earlier this month the agency would add new warning labels to the most widely prescribed painkillers and increasingly consult with outside advisers on the medications.

For years, the FDA has made only minor changes to its system for approving painkillers, despite record levels of abuse and death tied to the medications.

Whereas the FDA previously based its decisions on whether new drugs would benefit patients, Califf says the agency must now consider the broader effect on the country.

"The impact of addiction on all society is profound," Calif said. "I don't think anyone anticipated the magnitude of this effect."

In 2014, U.S. deaths linked to misuse and abuse of prescription painkillers climbed to roughly 19,000, the highest number on record, according to federal figures. Deaths tied to the drugs have risen more than four-fold since 1999 amid increased prescribing by U.S. doctors.

"I believe Dr. Califf understands the dire nature of the opioid epidemic and, accordingly, I believe he is today the right person to lead the FDA in a new direction," Senate Majority Leader Mitch McConnell, R-Ky., said this week.

Califf's nomination was initially expected to sail through the Senate, given his background as a highly-respected academic and clinical trial researcher for the pharmaceutical industry, a key interest group. But those industry ties proved a liability.

Democratic presidential candidate Bernie Sanders, and Democratic Sens. Joe Manchin of West Virginia and Ed Markey of Massachusetts held up Califf's nomination for several weeks in an effort to force the agency to be tougher on opioids and also prescription drug prices.

Manchin, Markey, Democratic Sen. Richard Blumenthal of Connecticut and Republican Sen. Kelly Ayotte of New Hampshire voted against the nomination.

"The FDA needs new leadership, new focus and a new culture," Manchin said.

In 2006, Califf founded the Duke University Clinical Research Institute, the world's largest contract research organization, which primarily works with pharmaceutical companies.

Sanders did not leave the campaign trail to vote on the nomination, but he said in a statement that he would have opposed it.

Ayotte is in a tough re-election campaign, and New Hampshire has a significant drug abuse problem. She said on the Senate floor Tuesday that "there is so much more we need to do" on the prescription drug issue.

"There isn't a place I go in my state where I don't hear from a mother, a father, a sister, a brother, a grandmother, a grandfather, a friend about someone who lost a loved one, lost someone they care about, because of heroin, opioids, Fentanyl, the deadly combination that is killing people," she said.

Despite the opposition, Califf's nomination enjoyed wide Republican support in a year in which many of Obama's nominees have been held up. Tennessee Sen. Lamar Alexander, the Republican chairman of the Health, Education, Labor and Pensions Committee, said he is confident that Califf can lead the agency "fairly and impartially."

The prior FDA commissioner, Dr. Margaret Hamburg, left the job early last year. The FDA's chief scientist, Dr. Stephen Ostroff, has served as acting head of the agency.