The invention relates to L-arginine, a derivative thereof or a pharmaceutically acceptable salt thereof for use as a laxative, for treatment of constipation and for clearing the rectum and/or the colon of a mammal. Compositions suitable for topical administration to an area of the gastrointestinal tract are provided. Orally administered preparations comprising for example an enteric coating that dissolves at a desired location in the gastrointestinal tract; a controlled release formulation; a sustained release formulation; a targeted drug delivery system; or a combination thereof are also provided.