What happened Pacira Pharmaceuticals (NASDAQ: PCRX) shares are down 15% at 12:00 p.m. EDT today following word that its pain medicine Exparel didn't perform as well as hoped in key phase 3 studies. So what Pacira Pharmaceuticals already markets the surgical-pain medicine Exparel, and its sales have been growing quickly as doctors embrace ways to control pain that may reduce a patient's need for rescue pain medications, like opioids. IMAGE SOURCE: GETTY IMAGES. The potential to expand Exparel's use into new indications has helped Pacira Pharmaceuticals' share price rally over the past year, but enthusiasm was tempered today when management reported less-than-spectacular results in using it as a nerve block in total knee arthroplasty, or TKA. Specifically, Exparel failed to statistically and significantly control pain in TKA patients. Management is blaming the failure on results from one center participating in the trial that didn't follow trial protocols; nevertheless, the data took the luster off positive trial results in patients undergoing shoulder surgery and rotator-cuff surgery. In the shoulder-surgery trial, Exparel significantly reduced pain, and it reduced the use of opioids in recovering patients, both with p-values of <0.0001. Now what Exparel's sales increased 11%, to $276.4 million last year, and that performance translated into non-GAAP earnings per share of $0.62. This year, Exparel sales are expected to be between $290 million and $310 million, up 9% from 2016, at the low end. Exparel's success suggests that, if results from these trials had been a slam-dunk success, it could've led to a speedy FDA green light that could drive sales and profit even higher. Management still thinks it has enough data to file for the label expansion, so it's possible an approval will still happen, but it's far less of a lock than it could've been.10 stocks we like better than Pacira PharmaceuticalsWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the 10 best stocks for investors to buy right now... and Pacira Pharmaceuticals wasn't one of them! That's right -- they think these 10 stocks are even better buys. Click here to learn about these picks! *Stock Advisor returns as of July 6, 2017Todd Campbell has no position in any stocks mentioned. His clients may have positions in the companies mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.