The Food and Drug Administration (FDA) on Friday denied a request from the maker of the painkiller Opana ER to block generic forms of the drug. The decision came as a surprise, Reuters reports.

The drug’s manufacturer, Endo Health Solutions, argued its newer tamper-resistant formula was more difficult to abuse than the original version of the drug, and asked that the agency not approve generic forms of the earlier version. The FDA decided that since the original Opana had not been withdrawn for reasons of safety or effectiveness, generic forms of the painkiller could continue to be approved and marketed.

The FDA also said the newer Opana ER could still be abused, and might be more easily injected than the original formulation.

“We are extremely disappointed and disagree with today’s decision, and believe that the approval of non-abuse deterrent formulations of long acting opioids will contribute to a significant increase in prescription drug abuse,” Rajiv De Silva, President and Chief Executive Officer of Endo Health Solutions, said in a news release.

Last month, the FDA announced it will not approve any generic versions of the original form of OxyContin. The move is aimed at preventing prescription drug abuse. The original version of OxyContin could be crushed and then snorted or injected. The FDA also approved new labeling for a reformulated version of the drug, which will indicate it is more difficult to crush, and thus harder to abuse than the original version. OxyContin’s manufacturer, Purdue Pharma, introduced the tamper-resistant formula in 2010.

Because of the FDA’s decision about generic versions of OxyContin, many experts thought the agency would make a similar ruling about Opana ER, the article notes.