Merck reported better-than-expected profit in the first quarter, driven by higher sales of its diabetes drug Januvia and heart drug Zetia.
The company also raised its full-year adjusted earnings forecast and narrowed its revenue forecast to account for changes in foreign exchange rates.
The 125-year-old company's stock was up marginally in premarket trading on Thursday.
Sales of Januvia rose 2.5 percent to $906 million in the quarter, while Zetia sales increased 7.7 percent to $612 million.
But, sales of Merck's arthritis drug Remicade slumped about 30 percent to $349 million. The drug is facing competition outside the United States from cheaper copycat versions.
Total revenue dipped about 1 percent due in part to a stronger dollar. Revenue fell to $9.31 billion from $9.43 billion, while analysts were expecting an increase to $9.46 billion.
Net income attributable to Merck rose to $1.12 billion, or 40 cents per share, from $953 million, or 33 cents per share, a year earlier.
Excluding items, Merck earned 89 cents, beating analysts average estimate by 4 cents, according to Thomson Reuters I/B/E/S.
Merck raised its full-year adjusted earning forecast to $3.65 to $3.77 per share from $3.60 to $3.75.
The drugmaker narrowed its sales forecast to $39.0 to $40.2 billion from $38.7 to $40.2 billion.