Pacira Pharmaceuticals Inc. said Thursday its surgical pain drug Exparel failed in a late-stage clinical trial, and its shares slumped 10 percent in after-hours trading.

The trial was designed to evaluate Exparel for use in blocking intercostal nerves, or nerves located between ribs, following surgeries that go through a patient’s ribs from the back. The trial was mostly performed in Europe. Pacira said patients in some countries responded positively to the drug. However, in other locations patients had a strong response to treatment with a placebo. Overall Exparel was not significantly better than the placebo at reducing pain in the first three days after surgery.

The Parsippany, N.J., company said it will continue to evaluate data from the trial.

Its shares dropped $3.51, or 10.3 percent, to $30.60 in late trading, after gaining 18 cents to $34.11 during regular trading. The stock reached an all-time high of $35.65 on July 23.

Patients in the study had had a posterolateral thoracotomy, a surgical procedure that is often used in operations on the lungs.

Exparel is a long-acting drug that is designed to treat pain for up to three days after surgery. It does not contain opioids. Pacira started selling Exparel in April 2012, and the drug posted sales of $10.4 million in the first quarter, the bulk of its total revenue.

The company is running additional trials of the drug in order to win new marketing approvals and improve sales. It is studying Exparel in blockage of the femoral nerve after total knee arthroplasties. The company said Thursday that it plans to file for marketing approval of Exparel in that indication in early 2014.