There's reason to celebrate for Celebrex. Pfizer (NYSE:PFE) announced today that the U.S. Patent and Trademark Office has added 18 months onto the pharmaceutical company's previous patent for the painkiller Celebrex. The "reissue patent" effectively extend's Pfizer's exclusive sales from May 30, 2014, to Dec. 2, 2015, and also includes pediatric exclusivity for a six-month period.

"Continued development of new medicines that enhance patient lives is supported by protecting intellectual property and innovation," said Pfizer General Counsel and Executive VP Amy Schulman in a statement today. "We are pleased with the reissuance of this patent protecting the invention of using celecoxib to treat osteoarthritis and other approved conditions, and have initiated legal proceedings to enforce our intellectual property rights through Dec. 2, 2015."

The USPTO had denied previous requests for patent reinstatement, and several generic-drug companies had been in various stages of the approval process to sell generic versions of Celebrex. Pfizer filed suit today against Teva Pharmaceutical (NYSE:TEVA), Mylan Pharmaceuticals (NASDAQ:MYL), Watson Laboratories, Lupin Pharmaceuticals USA, and Apotex for infringement of its newly reissued patent.

According to The Wall Street Journal, Celebrex pulled in $1.75 billion of 2012 U.S. sales and $2.72 billion worldwide.