The head of the Food and Drug Administration on Thursday defended the agency’s approval of Zohydro, a powerful prescription opioid made by Zogenix Inc, saying it offers a “unique” option to treat pain despite concerns about potential abuse.

The FDA’s approval of the drug has drawn a flood of criticism, including protests from the attorneys general of 28 states as well as dozens of groups representing doctors and addiction treatment specialists who are concerned that Zohydro will set off a wave of addiction similar to problems with the original form of OxyContin, another opioid.

These critics have petitioned the FDA to consider pulling the drug’s marketing approval.

FDA Commissioner Margaret Hamburg, testifying at a Senate hearing, acknowledged that Zohydro is “a powerful drug” but said “...that if appropriately used, it serves an important and unique niche with respect to pain medication and it meets the standards for safety and efficacy.”

Her comments to the Senate Health, Education, Labor and Pensions Committee come barely a week after Zogenix said it was making the painkiller available at “select pharmacies” following the drug’s FDA approval in October.

In approving the drug, the FDA overruled its panel of outside advisers, who had recommended against approval, citing safety concerns about the potential for abuse.

Shares of Zogenix rose more than 5 percent after Hamburg’s comments, before slightly paring gains to close up 4.6 percent at $3.67 on the Nasdaq.

In her comments at Thursday’s hearing, Hamburg said the FDA,

in approving Zohydro, recognized “...its addiction potential and understanding, of course, the broader context of the serious problem of opioid medication abuse and misuse in this country.”

Zogenix last week, in its statement on quarterly results, said it is “taking a measured approach to commercialization.” Representatives for Zogenix told Reuters on Thursday that the company had no further comment.

A recent study of government data found that, on average, more than 12 million people age 12 and older were estimated to have used prescription opioids at least once a year to get high.

Senators at the committee’s hearing echoed worries about abuse, noting the Zohydro is not made in a way to thwart crushing or chewing of such drugs to get a high.

“The concern that I think a number of us have ... (are) about the implications of allowing this new product on the market without these abuse deterrent properties,” said Senator Robert Casey, a Democrat from Pennsylvania on the panel.

Senator Joe Manchin of West Virginia, whose state has been particularly hard-hit by prescription drug abuse, earlier this week called on U.S. Health and Human Secretary Kathleen Sebelius to overturn the FDA’s approval.

“Americans are abusing, and (in) many cases dying, at an alarming rate from highly addictive pain medicine, and it is shameful that the FDA would ignore its own experts to approve this drug,” Manchin said in a statement after the hearing. He later introduced legislation that would ban Zohydro.

Hamburg said unlike other approved hydrocodone drugs, Zohydro does not contain acetaminophen, which can be toxic to the liver. She also said other factors, including doctors’ prescribing practices, play a role in drug abuse.

Abuse of OxyContin became so widespread that manufacturer Purdue Pharma changed its formula in 2010 so that the drug could not be injected or snorted as easily. On Wednesday, Purdue said it was moving ahead with an abuse-resistant rival to Zohydro.

Zogenix last week also said it is making progress on another version of Zohydro to deter abuse.

“I would love if we had abuse-deterrent formulations that were actually meaningful and effective at deterring abuse in all instances. We are moving in that direction,” Hamburg told lawmakers. “Right now, unfortunately, the technology is poor.”

She added that the FDA is working on guidelines to help manufacturers come up with more effective abuse deterrents but gave no timeline for when the guidelines would be finalized.

Developing more non-opioid pain drugs could also help prevent misuse, she said.

“Acute and chronic pain needs to be treated. Opiates are very effective for acute pain, less effective for chronic pain, but we don’t have a lot of good alternatives at the present time,” she told the Senate panel.

Hamburg also said more attention needs to be paid to the overdose-reversal medication called naloxone, which could save more lives if it was easier to use and more widely available.

The FDA is urging drugmakers to develop other forms of the injectable drug such as a nasal spray or an automatically injectable version, she added and has been encouraged by their response, she said.

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By Susan Heavey