Pharmaceutical giant Pfizer announced fourth-quarter earnings that missed analyst expectations Tuesday following a pair of recent acquisitions.

Net income in the fourth quarter was $775 million, compared with a loss of $172 million in the year-ago period. That translated into 47 cents per share, three cents below analyst expectations.

Revenues were $13.6 billion, down three percent from the year-ago period.

Pfizer, which completed purchases of Medivation and Anacor last year, said results were dented in part by patent expirations on popular drugs and the strong dollar.

Pfizer's best-known drugs include the sexual dysfunction medication Viagra, the cancer drug Ibrance and the pain drug Lyrica.

"I was pleased with the company's overall performance during 2016 and believe both of our businesses executed well despite a challenging operating environment," said chief executive Ian Read.

Pfizer projected 2017 adjusted, diluted earnings of $2.50 to $2.60 per share, compared with $2.40 in 2016.

Pfizer said it sees 2017 revenues at between $52 billion and $54 billion, compared with $52.8 billion last year.

Shares of Pfizer were down 0.7 percent to $31.08 in pre-market trade.