Merck's best selling drugs account for 60% of its global health sales:

Zocor Vioxx Cozaar and Hyzaar Fosamax Singulair

"The results look in line [with industry analysts' expectations], and their main products are still growing well," said Parker Hunter pharmaceutical analyst Richard Lawrence.

The recently launched arthritis drugs Vioxx and the arthritis fighting Zocor helped lift Merck's sales by 28% to $11.3bn during the period.

Sales of both drugs rose 31% during the quarter.

Top selling drugs

Combined sales of the company's top drugs rose 30% during the period compared to the first quarter of 2000, said the company's boss Raymond Gilmartin.

Net income rose to $1.66bn, from $1.5bn during last year's first quarter.

The asthma drug Singulair and the osteoporosis drug Fosamax also sold well, up 70% and 27% respectively.

Sales of the hypertension drugs Cozaar and Hyzaar, which are typically administered together, rose 5%.

Worries put to rest

Ahead of the results, investors had been concerned about the effect on the company's bottom line of several recent and forthcoming patent expirations for some of its main drugs, for example its ulcer drugs Pepcid and Prilosec.

But the strong sales of Vioxx seemed to convince them that new drugs were coming through the pipeline to replace yesterday's best sellers, analysts said.

Merck's own predictions for the rest of the year's profits were in line with analysts' predictions.

However, Mr Gilmartin acknowledged that it is reasonable to assume that the strong growth seen so far this year "may be stronger than the growth rates for the remaining three quarters of the year".

Ailing stock

Merck's share price has fallen 16% this year after having reached a historic high in November 2000.

The decline is sharper than the 15% drop recorded by the American Stock Exchange Pharmaceutical Index.

When the markets closed in the US on Thursday, the share was worth $78.27.The stock closed almost $5 lower at $73.6 on the New York Stock Exchange on Friday.