Pfizer, the world's biggest drug maker, said its first-quarter profit fell 19% from a year earlier due to generic competition for its blockbuster anti-cholesterol pill Lipitor.

Pfizer said net income was $1.8 billion in the first three months of the year, or 24 cents per share, compared with $2.2 billion the same time last year.

Excluding special items, Pfizer earned 58 cents per share, better than the 56 cents forecasted by analysts.

Revenue fell 7% from a year ago to $15.4 billion, slightly below Wall Street expectations of $15.5 billion. 

US revenues fell 15% to $6 billion, mainly as a result of the US loss of exclusivity of Lipitor on November 30, 2011, the New York-based Pfizer said.

International revenues were $9.5 billion, stable compared with the 2011 first quarter. In emerging markets, revenues jumped 9%, driven by surging sales mainly in China, Mexico and Russia.

"I am pleased with our first-quarter 2012 financial performance, which was driven primarily by growth in certain brands including Celebrex, Enbrel and Lyrica, growth in key geographies such as China, as well as our continued ability to realize cost savings and efficiently allocate our shareholders' capital," Ian Read, chairman and chief executive, said.

Pfizer lowered its full-year adjusted profit forecast to take into account the sale last month of its infant food maker Pfizer Nutrition to Swiss food giant Nestle, for $11.85 billion.

The company said it expects earnings per share of $2.14 to $2.24, down six cents from its earlier estimate. Analysts previously had forecast $2.26.