Pfizer reportedly will acquire King Pharmaceuticals and King’s Alpharma Animal Health.

It is a $3.6 billion deal that’s meant to shore up the portfolio of the world's largest drug company, it includes both human-health and animal-health products.

The deal to buy King Pharmaceuticals is Pfizer's largest purchase since it bought rival Wyeth for $68 billion in 2009.

Pfizer already has a large stake in the human pain drug market with its drugs Lyrica and Celebrex, which combined for more than $5 billion in sales in 2009. But now the company is betting that King's work on "abuse-resistant" pain drugs will pay off and help make up for the revenue Pfizer will lose in a few years when top sellers such as the cholesterol drug Lipitor no longer have patent protection.

King markets one such drug, called Embeda, and it's seeking approval for two others under the names Remoxy and Acurox. Remoxy is similar to Purdue Pharma LP's OxyContin, the top-selling human painkiller in the U.S. Both are designed to treat pain by slowly releasing the narcotic oxycodone. 

According to Pfizer, King's key businesses are not only complementary to Pfizer's businesses, but are also strategically aligned with Pfizer's Primary Care, Established Products and Animal Health business units, enabling a seamless combination that will maximize King's assets with Pfizer's global organization's scale and resources.

Pfizer officials anticipate the transaction to yield initial cost savings from operating expenses of at least $200 million, which are expected to be fully realized by the end of 2013. The transaction is not expected to impact Pfizer's 2010 financial guidance. Also, the tender offer is subject to regulatory approval in the U.S. and other jurisdictions.

(Parts of this report were contributed by The Associated Press)