Lactulose Suspension is a laxative that treats constipation by drawing water into the bowels thereby making stools softer and easier to pass. This medicine takes a couple of days to work (up to 3 days). Take it as instructed even it appears not to be working. Talk to your doctor if you are still constipated after 3 days. Constipation is a common problem that can cause significant pain and discomfort. This medicine can relieve discomfort and improve your quality of life. To prevent constipation from happening it may help to eat more high-fiber foods including fruit and vegetables and drink plenty of water.