State Representative John Lawn, a Watertown Democrat, was arrested early Wednesday on drunken driving charges outside the State House.

Massachusetts State Representative John Lawn will lose his license for 45 days after changing his plea in his drunk driving case.

Boston police said that Lawn, a 56-year-old Democrat who chairs the influential health care financing committee, was arrested at about 1:45 a.m. with the assistance of Massachusetts State Police.