Lactulose oral solution is a prescription drug that’s available as the brand-name drugs Enulose and Generlac. It’s also available as a generic drug. Generic drugs usually cost less. In some cases, they may not be available in every strength or form as the brand-name versions. Lactulose also comes as a rectal solution. This is only given as an enema by a healthcare provider. Why it’s used Lactulose is used to treat constipation. It’s also used to treat a brain problem called portal-systemic encephalopathy. This problem is a complication of severe liver disease. This drug may be used as part of a combination therapy. This means you may need to take it with other medications. How it works Lactulose belongs to a class of drugs called laxatives. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions. Lactulose is a synthetic (man-made) sugar. It breaks down in your large intestine and then draws water into the intestine. This softens your stool, which helps ease constipation. This drug also treats high ammonia levels in the blood due to liver disease. High ammonia levels can lead to portal-systemic encephalopathy. This drug works by drawing ammonia from your blood into your large intestine. Your large intestine then removes the ammonia from your body through your stool.