Pfizer Inc.'s fourth-quarter profit more than quadrupled, despite competition from generic drugs hurting sales, because of a $4.8 billion gain from selling its nutrition business.

The world's biggest drugmaker said Tuesday that its net income was $6.32 billion, or 85 cents per share, up from $1.44 billion, or 19 cents per share, a year earlier.

Excluding one-time items, the Viagra maker would have had a profit of $3.51 billion, or 47 cents per share — 3 cents more than analysts surveyed by FactSet were expecting.

The New York-based company's stock rose 4 cents to $2688 in premarket trading.

Revenue fell 7 percent to $15.1 billion, mainly due to generic competition to cholesterol blockbuster Lipitor. Analysts expected $14.35 billion.

Lipitor, which had reigned as the world's top-selling drug ever for nearly a decade, got U.S. generic competition in December 2011 and now has generic rivals in many major markets. The drug had been bringing Pfizer nearly $11 billion a year before then, down from its peak of $13 billion a year.

In the fourth quarter, Lipitor sales plunged 91 percent in the U.S. and 71 percent worldwide, to $584 million. A dozen other medicines also had lower sales due to generic competition. But key newer drugs had double-digit sales increases, including fibromyalgia and pain treatment Lyrica, at $1.13 billion, painkiller Celebrex at $750 million, and the Prevnar 13 vaccine against meningitis and other pneumococcal infections, at $993 million.

Altogether, Pfizer's prescription drug revenue fell 9 percent in the quarter, to $12.89 billion. The animal health business, which Pfizer is planning to spin off, saw revenue increase 6 percent, to $1.17 billion. The consumer health business, which sells Centrum vitamins, had revenue jump 16 percent, to $936 million.

Pfizer said this year it expects earnings per share of $2.20 to $2.30, excluding one-time items, and revenue of $56.2 billion to $58.2 billion. Analysts are expecting $2.28 per share and revenue of $57.55 billion.

For the full year, net income was $14.57 billion, or $1.94 per share. That was down from $10.01 billion, or $1.27 per share, in 2011. Revenue totaled $58.99 billion, down 10 percent from $65.26 billion in 2011, before generic competition slashed sales of Lipitor and schizophrenia drug Geodon.