Lactulose operates like the other osmotic laxatives above, but it is available only by prescription. Brand names include Cephulac, Chronulac, Constilac, Cholac, Constulose, Duphalac, Enulose ...

Osmotic laxatives draw water into the bowel because they are hypertonic, essentially flushing the colon. Examples of osmotic laxatives include milk of magnesia (which also softens stools), sodium ...