Laxatives, purgatives, or aperients are substances that loosen stools and increase bowel movements. They are used to treat and prevent constipation. Laxatives vary as to how they work and the side effects they may have. Certain stimulant, lubricant and saline laxatives are used to evacuate the colon for rectal and bowel examinations, and may be supplemented by enemas under certain circumstances. Sufficiently high doses of laxatives may cause diarrhea. Some laxatives combine more than one active ingredient. Laxatives may be administered orally or rectally. Types
Bulk-forming agents
Bulk-forming laxatives, also known as roughage, are substances, such as fiber in food and hydrophilic agents in over-the-counter drugs, that add bulk and water to stools so that they can pass more easily through the intestines (lower part of the digestive tract).Properties

Site of action: small and large intestines
Onset of action: 12–72 hours
Examples: dietary fiber, Metamucil, Citrucel, FiberConBulk-forming agents generally have the gentlest of effects among laxatives, making them ideal for long-term maintenance of regular bowel movements. Dietary fiber
Foods that help with laxation include fiber-rich foods.
Dietary fiber includes insoluble fiber and soluble fiber, such as:
Fruits, such as bananas, though this depends on their ripeness, kiwifruits, prunes, apples (with skin), pears (with skin), and raspberries
Vegetables, such as broccoli, string beans, kale, spinach, cooked winter squash, cooked taro and poi, cooked peas, and baked potatoes (with skin)
Whole grains
Bran products
Nuts
Legumes, such as beans, peas, and lentils

Emollient agents (stool softeners)
Emollient laxatives, also known as stool softeners, are anionic surfactants that enable additional water and fats to be incorporated in the stool, making it easier for them to move through the gastrointestinal tract. Properties

Site of action: small and large intestines
Onset of action: 12–72 hours
Examples: Docusate (Colace, Diocto), Gibs-EzeEmollient agents prevent constipation rather than treating long-term constipation. Lubricant agents
Lubricant laxatives are substances that coat the stool with slippery lipids and decrease colonic absorption of water so that the stool slides through the colon more easily. Lubricant laxatives also increase the weight of stool and decrease intestinal transit time.Properties

Site of action: colon
Onset of action: 6–8 hours
Example: mineral oilMineral oil is the only nonprescription lubricant. Mineral oil may decrease the absorption of fat-soluble vitamins and some minerals.One example is Liquid paraffin.