Medco Health Solutions Inc. said Tuesday it extended its contract to provide pharmacy benefit services to health insurer UnitedHealth Group Inc.

The contract will be valid through 2012 but the company did not disclosed details of it. Analysts estimate the contract totaled about 20 percent of Medco's revenue in 2007.

Shares of Franklin Lakes, N.J.- based Medco rose 6.05 percent to $50.67 on the New York Stock Exchange by 3:40 p.m. on Tuesday. Earlier shares rose as much as 8.1 percent.

UnitedHealth shares dropped 10.69 percent or $4.01 to $33.77 on the New York Stock Exchange as the larges U.S. health insurer reduced its profit forecast for 2008.