WASHINGTON – An abuse-resistant form of the powerful but controversial painkiller OxyContin won’t be ready next year as its manufacturer had hoped.

The widely prescribed narcotic painkiller is considered important therapy for many patients suffering long-term moderate to severe pain from cancer or other illnesses. When swallowed whole, one tablet provides 12 hours of pain relief.

But if chewed, inhaled or injected, OxyContin produces a quick – and potentially lethal – heroin-like high. It has been linked to more than 100 deaths.

Manufacturer Purdue Pharma is trying to create abuse-resistant forms by adding drugs that would block the buzz if OxyContin is taken the wrong way.

One method under consideration is to put the narcotic blocker naloxone in OxyContin tablets. If the tablets are crushed and injected, naloxone would enter the bloodstream to block the OxyContin’s effects.

That wouldn’t block other forms of abuse, but Purdue Pharma had called it an important interim step that it hoped to begin selling next year.

A competing painkiller, Talwin NX, uses that approach.

But on Tuesday, Purdue Pharma announced that clinical trials found, among other problems, that naloxone sometimes blocked pain relief for patients who took the combination tablets correctly. Purdue Pharma said it won’t be seeking Food and Drug Administration approval this year, and will do further research to see if naloxone is worth pursuing.