Zoetis Inc. is an American drug company, the world's largest producer of medicine and vaccinations for pets and livestock. The company was a subsidiary of Pfizer, the world's largest drug maker, but with Pfizer's spinoff of its 83% interest in the firm it is now a completely independent company. The company directly markets its products in approximately 45 countries, and sells them in more than 100 countries. Operations outside the United States accounted for 50% of the total revenue. Contemporaneous with the spinoff in June 2013 S&P Dow Jones Indices announced that Zoetis would replace First Horizon National Corporation in the S&P 500 stock market index.