BOSTON (Reuters) - A U.S. drug distribution company charged Canada's Biovail Corp (BVF.TO: Quote, Profile, Research) and Britain's GlaxoSmithKline (GSK.L: Quote, Profile, Research) with violations of antitrust laws in a suit filed in Boston federal court on Thursday.

American Sales Co, of Erie, New York, charged in papers filed in U.S. District Court that Biovail and Glaxo filed "baseless" patent-infringement lawsuits and petitions with U.S. regulatory authorities to block generic competitors to a branded antidepressant drug from coming to market.

It charges that Biovail and Glaxo "engaged in sham litigation and petitioning and entered into anti-competitive agreements to improperly maintain their monopoly profits" for the drug, sold under the brand name Wellbutrin XL. It also claims the companies entered into agreements with developers of generic competitors to delay their entry into the market.

Generic drugs typically cost less than their branded counterparts, making them a popular alternative with consumers and pharmacy benefit managers.

The suit, which charges violation of the U.S. Sherman Act, seeks unspecified monetary damages.

Officials at Biovail and Glaxo could not be reached for immediate comment.

(Reporting by Scott Malone; Editing by Brian Moss)