Watson Pharmaceuticals

(WPI)

said Wednesday it filed an antitrust lawsuit against

Bristol-Myers Squibb

(BMY) - Get Report

, claiming the pharmaceuticals giant unlawfully blocked competition to its anti-anxiety medicine BuSpar.

The Watson suit comes on the heels of a federal court judge's ruling Tuesday night that said Pittsburgh-based

Mylan Laboratories

(MYL) - Get Report

would not infringe on patent laws by manufacturing a generic version of BuSpar, a medication used to treat generalized anxiety disorder.

A spokeswoman from Bristol-Myers said the company was surprised by the court's decision and has filed for a stay of its order while it prepares for an appeal. The company would not comment on the Watson suit except to confirm it had been served with court papers.

Shares of Bristol-Myers were down $2.22, or 3.6%, to $58.78 in recent trading on the

New York Stock Exchange

. Shares of Watson were up 55 cents to $55.05, and Mylan shares fell 41 cents to $22.34.