Manevac granules belongs to the group of medicines known as stimulant laxatives. Manevac granules are used to treat constipation. They work by encouraging the bowel to contract and move the waste products along the bowel helping you to go to the toilet. Constipation can be caused by a poor diet, not drinking enough water and not going to the toilet as soon as you feel you need to. Pregnancy, a lack of exercise or movement (such as being ill in bed) and some medicines, including some pain killers, can also cause constipation.