Wyeth ( WYE) reported a 12% rise in first-quarter earnings compared with the year-ago quarter. However, sales of the company's top-selling drug, the antidepressant Effexor, slid 6%. Wyeth lost 67 cents, or 1.2%, at $55.66.

Other health care providers lost ground as well. MedcoHealth ( MHS) was down 1.8%, Coventry Health ( CVH) slid 1.2%, and WellPoint ( WLP) was off 1.8%.

Medical-device makers were also under pressure. Stryker ( SYK) beat first-quarter earnings targets after reporting results following Wednesday's close, but the stock fell $3.09, or 4.5%, to $66.01.

Among other device makers, Zimmer Holdings ( ZMH) shed 2.1%, and Boston Scientific ( BSX) was off 0.7%.

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