(Adds company response, analyst comment; sales figures)
WASHINGTON, June 8 (Reuters) - As the United States battles a growing opioid abuse crisis, the Food and Drug Administration on Thursday asked Endo International Plc to withdraw from the market its long-lasting opioid painkiller, Opana ER, sending Endo's shares down more than 12 percent.
The move marks the first time the agency has called for the removal of an opioid painkiller for public health reasons and comes after a panel of advisers concluded in March that the drug's benefits did not outweigh the risks.
"We are facing an opioid epidemic - a public health crisis, and we must take all necessary steps to reduce the scope of opioid misuse and abuse," Dr. Scott Gottlieb, the FDA's newly appointed commissioner said in a statement.
Opioids were involved in more than 33,000 deaths in 2015 and opioid overdoses have quadrupled since 1999, according to the Centers for Disease Control and Prevention.
It remains to be seen whether Endo will comply with the FDA's request. The company said in a statement it is "evaluating the full range of potential options as we determine the appropriate path forward."
If Endo refuses to withdraw the product, the FDA could offer the company an opportunity for a hearing to make the case for why the product should not be removed. If, after the hearing, the FDA decided to withdraw its approval, Endo could, in theory, sue the agency.
"Despite the FDA's request to withdraw Opana ER from the market, this request does not indicate uncertainty with the product's safety or efficacy when taken as prescribed," the company said.
Opana ER was approved in 2006 and a reformulated version was introduced in 2012.
In March a panel of advisers to the FDA voted 18-8, with one abstention, that the drug's benefits no longer outweighed the risks. Data showed that while nasal abuse rates fell, the rate of intravenous abuse increased.
The drug has also been associated with a serious outbreak of HIV and hepatitis C, the agency said, as well as a serious blood disorder known as thrombotic microangiopathy.
"If Endo resists taking this off the market immediately, the people who are injured or killed as a result of it being on the market longer than it should, there will be a wave of product liability litigation against the company," said Sidney Wolfe, founder and senior adviser to consumer watchdog Public Citizen.
Ohio filed a lawsuit in May against the pharmaceutical industry, charging that a number of companies, including Endo, Purdue Pharma, Teva Pharmaceutical Industries Ltd, Johnson & Johnson and Allergan Plc conducted misleading marketing campaigns that downplayed the drugs' addictiveness. Other states and cities have filed similar lawsuits.
Gottlieb said the agency will "continue to take regulatory steps when we see situations where an opioid product's risks outweigh its benefits, not only for its intended patient population but also in regard to its potential for misuse and abuse."
Randall Stanicky, an analyst at RBC Capital Markets, said Opana ER is a declining asset whose sales are expected to fall to $97 million in 2019, down from an estimated $134 million in 2017.
Endo's shares fell 12.2 percent to $12.10 in extended trading.
(Reporting by Toni Clarke in Washington; additional reporting by Ankur Banerjee; Editing by Chris Reese and Lisa Shumaker)