Merck & Co said its fourth-quarter profit fell 7% as generic competition slashed sales of its blockbuster allergy drug Singulair.

The drugmaker also said it took sizeable restructuring and acquisition charges.

The world's third biggest drugmaker by revenue said net income was $1.4 billion, or 46 cents per share, down from $1.51 billion, or 49 cents per share, a year earlier.

Excluding one-time charges totaling $1.14 billion, net income was $2.54 billion, or 83 cents per share, 2 cents more than analysts were expecting.

The maker of Januvia and other diabetes pills said revenue totalled $11.74 billion, down 5% from 2011's fourth quarter.

Analysts expected revenue of $11.47 billion. US-based Merck forecast 2013 earnings per share of $3.60 to $3.70, excluding charges.