Net income dropped to $473.9 million, or 22 cents a share, from $1.12 billion, or 51 cents, a year earlier. Revenue in the quarter rose to $6.04 billion.
Zocor sales fell by 65% due to generic competition form cheaper alternatives after the patent on the cholesterol treatment expired in June.
In contrast, sales of Merck's newer cholesterol drugs, Vytorin and Zetia, rose 46% to $1.1 billion.
“The impressive sales performance of our newer and in-line products coupled with the rapid uptake of new, first-in-class vaccines and medicines like Gardasil and Januvia, speaks to the strength of our underlying business and product portfolio,” said Richard Clark, CEO and president of Merck.
However, Merck's falling profit also took a hit from its takeover of Sirna Therapeutics, with a charge of $466 million. Merck acquired Sirna for $1.1 billion in order to gain its gene-silencing technology.
Earnings were also hurt by the cost of lawsuits relating to the withdrawn drug Vioxx. Many Vioxx uses are alleging that they suffered heart attacks as a result of taking the drug. The company reported a $75 million charge in the fourth quarter to fund the legal costs.