Merck's hepatitis C treatment Zepatier had sales of $378 million, topping analysts' estimates of $269 million, while sales of $532 million for Gardasil vaccine against human papillomavirus also sailed past Wall Street forecasts. Animal health sales grew 13 percent to $939 million.

The company cautioned that animal health growth would be "more measured in subsequent quarters."

Excluding items, Merck earned 88 cents per share, beating analysts' average estimate by 5 cents, according to Thomson Reuters I/B/E/S.

Merck shares were up 10 cents at $62.48.

(Reporting by Bill Berkrot in New York and Natalie Grover in Bangaluru; Editing by Savio D'Souza, Bernard Orr)