(Adds background, information from court ruling and company, share activity, in paragraphs 2, 7 and 9)
By Susan Kelly and Natalie Grover
April 15 (Reuters) - A U.S. District Court judge on Tuesday stopped Massachusetts from implementing a ban on the sale of Zogenix Inc's prescription painkiller Zohydro, saying federal law superseded the state's action.
The company's shares climbed about 9 percent to $2.54 in after-hours trading.
Massachusetts Governor Deval Patrick had announced a ban on the drug, formally declaring a public health emergency on March 27 stemming from abuse of opioids in the New England state.
The U.S. District Court for Massachusetts granted a preliminary injunction against the ban, saying that by imposing its own conclusion about the safety and efficacy of Zohydro, the state was obstructing the U.S. Food and Drug Administration's constitutionally mandated charge.
The federal court order goes into effect on April 22.
"Although the ban may prevent someone from misusing the drug, the ban prevents all in need of its special attributes from receiving the pain relief Zohydro ER offers," Judge Rya Zobel said.
The injunction comes in the midst of a furor over Zohydro as the United States grapples with a rise in opioid abuse. The class of drugs includes not only powerful prescription painkillers but also heroin. Massachusetts has seen a spike in the number of opioid- and heroin-related deaths.
Zohydro, an extended-release form of hydrocodone, has come under scrutiny from members of the U.S. Congress, state attorneys general, medical groups and drug treatment experts seeking to block its use.
Although intended for release over a 12-hour period, the medicine can be crushed and inhaled or injected, making a full dose available immediately.
FDA last year approved Zohydro, Zogenix's sole product on the market, despite concerns from an advisory panel over the drug's potential for abuse.
Zogenix maintains the drug is a necessary option for patients with severe, around-the-clock pain who cannot tolerate acetaminophen.
"Today's legal ruling was a positive step forward for Massachusetts patients," said Zogenix Chief Executive Roger Hawley.
Unlike competing products such as AbbVie Inc's Vicodin and UCB's Lortab, Zohydro does not contain acetaminophen, which has been linked to liver damage.
FDA, in a statement, said it is following the legal proceedings in Massachusetts and remains concerned about efforts by states to ban FDA-approved drugs.
"Both the prevention of prescription opioid abuse and appropriate pain management are top public health priorities at FDA. Actions to advance one should not impede the other," the agency said.
The case was in Re: Zogenix Inc vs Deval Patrick in the U.S. District Court, District of Massachusetts, No. 14-11689-RWZ (Reporting by Susan Kelly in Chicago and Natalie Grover in Bangalore; Additional reporting by Toni Clarke in Washington; Editing by Savio D'Souza, Jonathan Oatis and Mohammad Zargham)