Updated from 1:57 p.m. EDT

Shares of BioMarin ( BMRN - Get Report) were among the worst-performing health and pharmaceutical stocks Wednesday, falling 15.2% after the company warned that 2004 losses would be wider than expected.

The biopharmaceutical company now expects full-year losses of $137 million to $140 million, higher than the $112 million to $114 million it previously forecast. The company did not provide expectations on a per-share basis. Analysts polled by Thomson First Call are expecting a full-year loss of $1.06 a share on sales of $26.4 million. BioMarin said that lower-than-expected sales from its Orapred product led to the earnings revision. Shares of BioMarin traded down 93 cents to $5.21.

Pain Therapeutics ( PTIE) fell 9.1% after the company said it would sell 8 million shares. The biopharmaceutical company also plans to offer underwriters a 30-day option to purchase an additional 1.2 million shares. The sale is being done under a shelf registration. Shares traded down 72 cents to $7.19.

Shares of Alpharma ( ALO - Get Report) traded actively after Pfizer ( PFE - Get Report) filed a preliminary injunction to block the company's marketing of gabapentin, a generic drug that's used to treat epilepsy. A hearing date has been set for Sept. 24. Last week, Alpharma rose after an appellate court vacated its stay order regarding the launch of gabapentin capsules. Gabapentin is the generic version of Neurontin, which is a Pfizer epilepsy drug that had sales of $2 billion in 2003. Shares of Alpharma traded up 20 cents, or 1.1%, to $17.85.

Exelixis ( EXEL - Get Report) fell 9.1% after J.P. Morgan downgraded shares of the company to neutral from overweight. The analyst cited the biotechnology company's recent price run-up for the ratings cut, saying that shares of Exelixis have appreciated much more than its peers' shares. The firm also said that other companies in Exelixis' space now offer more-compelling valuations. Shares traded down 82 cents to $8.22.

Other health care volume movers included Teva Pharmaceutical ( TEVA), down $1.07 to $26.13; Amgen ( AMGN), down 99 cents to $57.57; Schering-Plough , down 23 cents to $19.02; Merck ( MRK), down 9 cents to $44.75; Johnson & Johnson ( JNJ), down 60 cents to $57.30; and Genentech up 30 cents to $54.27.