Covidien plans to spin off its pharmaceuticals division into a separate company. The independent division can better compete in the growing pain-management area, the company announced. The drugs division generates more than $2 billion in sales each year. Among its products are Exalgo, a 24- hour extended release opioid, and Pennsaid, a topical anti-inflammatory medication. The company’s medical products business has annual sales of about $9.6 billion, according to the firm.