Malvern-based Endo Health Solutions Inc. dealt Monday with the fallout from an adverse decision Friday by the Food and Drug Administration, which rejected Endo's complicated request to deny approval to generic competitors of Endo's opioid painkiller, Opana ER.

After falling 5 percent on Friday, the company's stock fell 3.6 percent Monday, closing at $33.71.

Endo said Friday that the FDA decision might mean $120 million less in revenue for the rest of 2013 and that the company was "actively pursuing cost-reduction actions that will reduce the earnings effect of FDA's decision."

Asked about layoffs on Friday, Endo spokesman Blaine Davis wrote via e-mail, "We are evaluating all options based on the decision."

The company did not respond to requests Monday for additional comment.

In an unusual step, trading of Endo shares on the NASDAQ was halted Friday afternoon because of word that the FDA would issue a decision in a months-long process. After the market closed, the FDA posted its decision, and the company responded with a statement.

Opioid painkillers have passed cocaine and heroin as the leading cause of death by overdose in America.

Beside swallowing extra pills, those abusing the drug have crushed, liquefied, heated, smoked, and injected it.

With the growing governmental and public awareness of the overdose problem, Endo took the unusual step of pulling Opana ER from the market. After introducing what it said was a more tamper-resistant pill, the company petitioned the FDA to declare that the earlier version of Opana had been withdrawn for safety reasons. Such a finding by the FDA would have required the withdrawal of generic competitors.

Several weeks ago, the FDA approved a similar request by Purdue Pharma, which makes the formerly top-selling opioid painkiller OxyContin. But the FDA denied Endo's request and said that the new version of Opana ER might be more easily abused in some situations.

Chief executive officer Rajiv De Silva, who joined Endo in March, said that the company was "extremely disappointed" and that the previous financial predictions for the company assumed a favorable FDA decision.