Pacira Pharmaceuticals Inc. said Thursday sales of its surgical pain drug Exparel improved in the fourth quarter, but it took a bigger loss as spending increased.

Pacira started selling Exparel in April as a treatment for pain after surgery. It said sales rose to $7.8 million in the latest quarter, up from $4.6 million in the third quarter. The company is studying additional uses of Exparel and is also researching treatments for cancer and rheumatoid arthritis.

The company lost $16.3 million in the latest quarter after taking a loss of $15.3 million a year ago. Because Pacira sold additional shares of stock in 2012, its per-share loss decreased to 50 cents from 72 cents. Revenue rose to $10.5 million from $4.2 million.

Analysts forecast a loss of 41 cents per share and $9.8 million in revenue, according to FactSet.

Shares of Pacira Pharmaceuticals fell 74 cents, or 2.9 percent, to $25.18 in morning trading. The stock reached an all-time high of $26.38 on Wednesday.

Pacira is studying Exparel as a treatment for pain following robotic prostatectomy procedures, certain types of chest surgeries, and total knee arthroplasties. In December the company announced a partnership with Aratana Therapeutics, which will study the drug as a treatment for use on animals, starting with pets.

For 2012, the company lost $52.3 million, or $1.72 per share, after losing $43.3 million, or $2.64 per share, in 2011. Revenue grew to $39.1 million from $15.7 million.