Feb 11 (Reuters) - Specialty pharmaceuticals company Mallinckrodt Plc said it would buy Cadence Pharmaceuticals Inc for about $1.3 billion to acquire Cadence's pain drug Ofirmev.

Mallinckrodt will pay $14 in cash per Cadence share, representing a premium of about 27 percent over Cadence's last close.

"Ofirmev's growth is driven by an expanding base of physicians who are prescribing the product for an increasing number of surgical patients," Mallinckrodt CEO Mark Trudeau said.

"The product will be an outstanding addition to the brands component of Mallinckrodt`s specialty pharmaceutical segment," Trudeau said in a statement.