Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: King Pharmaceuticals (NYSE: KG) shares are up nearly 40% today after it was announced the company would be purchased by Pfizer Inc. (NYSE: PFE).

So what: Pfizer will pay $3.6 billion in cash for King, the maker of the Flector Patch and Embeda. The $14.25 price per share represents a 40% premium from Monday's price.

Now what: Pfizer has been looking for new products to soften the loss of exclusivity for Lipitor. With King, Pfizer also gets development partnerships with Pain Therapeutics (Nasdaq: PTIE) and Acura Pharmaceuticals (Nasdaq: ACUR). This is a great selling opportunity for King Pharmaceuticals shareholders who have seen their shares nearly double since early July.

Interested in more info on King Pharmaceuticals? Add it to your watchlist by clicking here.

Fool contributor Travis Hoium does not have a position in any company mentioned. Pfizer is a Motley Fool Inside Value pick. Try any of our Foolish newsletter services free for 30 days. True to its name, The Motley Fool is made up of a motley assortment of writers and analysts, each with a unique perspective; sometimes we agree, sometimes we disagree, but we all believe in the power of learning from each other through our Foolish community. The Fool has a disclosure policy.