The global recession continued to take a toll on the drug maker Merck’s (MRK: 23.7275, -1.5425, -6.1%) business in the first months of 2009, as the company saw sales of its most popular and lucrative cholesterol and cancer drugs evaporate during the quarter.

The Whitehouse Station, N.J.-based company said it earned $1.45 billion last quarter, or 67 cents a share, down 56% from $3.33 billion, or $1.52 a share, from a year ago.

On an adjusted basis, Merck said it earned 74 cents a share during the first quarter; three cents shy of the 77 cents expected by analysts, according to Thomson Reuters. The adjusted earnings included a 7-cent charge related to its merger and related costs with Schering-Plough (SGP: 22.16, -0.88, -3.82%).

Merck’s total sales during the quarter fell by 8% to $5.4 billion, well short of the $5.76 billion expected by analysts.

In a statement, Merck’s President, Chairman and Chief Executive Richard Clark said last quarter’s results “reflect the impact of the difficult global economy on patients, providers, and payers.”

Shares of Merck were down 7% on Tuesday, and are down more than 21% year to ate.

The drug company’s weakness could be seen in the company’s most prominent drugs. Sales of the popular Zetia and Vytorian cholesterol medications dropped by 23% during the quarter to $945 million compared to a year ago.

Merck’s cervical cancer vaccine, commonly known as Gardasil, saw sales fall by 33% compared to last year, to $262 million. The popular asthma drug Singulair saw sales drop 4% to $1.1 billion.

One drug that did do well during the quarter was Merck’s diabetes drug Januvia, which saw sales rise 51% from a year ago to $411 million.

The drop in sales for both of those drugs could be an indication of American consumers, who often lost their health insurance or are cutting back on discretionary purchases, stopped using the high profit margin, brand name drugs that Merck offers and switched to generics. Merck said it expects flat sales for Gardasil for 2009.

There was also disappointing news out of Merck’s already troubled drug development pipeline. Merck said it would be withdrawing its application for Food and Drug Administration approval for its experiment migraine drug MK-0974, citing an increase in liver disease among patients.

Despite the disappointing news in its pipeline and the decrease in sales, Merck reiterated its full-year forecast of $3.15 to $3.30 a share. The company did reduce its revenue forecast to $23.2 billion from $23.5 billion, saying it would make up the cut in revenue through cost cuttin