Despite investigations into the composition of its key drug, Acthar gel, as well as into its marketing practices, Questcor Pharmaceuticals (UNKNOWN:QCOR.DL) has announced that it is being bought by Mallinckrodt (NYSE:MNK) for $5.6 billion. Short-sellers have been attacking Questcor relentlessly recently, alleging that the stock could, in fact, be worth nothing if Acthar's composition is found not to be what the company claims.

In this video, Motley Fool health-care analyst David Williamson looks at the purchase, which was at a 27% premium to the stock's price, and discusses the pros and cons for Mallinckrodt. He also tells Questcor bulls everywhere that this signals the end of the battle for Questcor investors, and that they've officially won the fight on this stock over the bears.

David Williamson and The Motley Fool have no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.