How Laxatives Treat Constipation


A laxative is any substance that affects the intestines in a way that brings about a bowel movement. For mild constipation, a natural laxative or a bulk-forming laxative might be helpful in promoting a bowel movement. Harsher medication laxatives may also work to alleviate constipation, but most physicians warn against using them on a regular basis because they can cause harm to the bowels.


What Laxatives Are

Very broadly, a laxative is any type of food, medication, or supplement that will cause a person to have a bowel movement. Laxatives vary widely both in their form and in their effectiveness. Laxatives that are prescribed for use before a colonoscopy, for example, are going to work quicker and with more vigor than ones that are used for a case of mild, infrequent constipation. In all cases, laxative medications need to be used with care, because even though they are available over-the-counter, they can be harmful when not used properly.

Laxative medications are typically given in liquid, pill, or suppository form and may be prescribed to treat constipation that is not responding to other treatments. The use of laxatives (except bulk-forming laxatives) on a regular basis is typically not recommended, except in certain circumstances and on the advice of a physician. A physician will be able to make the determination as to which laxative will be most effective in each particular case.


Several types of laxatives are available over-the-counter in drug stores. They work in different ways.

  • Bulk-forming laxatives. This type of laxative, which includes such brand names as FiberCon, Metamucil, and Citrucel, are made of a type of fiber that is not absorbed by the intestine. Because the fiber in these supplements are not absorbed by the intestines, they pass all the way through the digestive tract. This type of fiber absorbs water and softens the stool, which makes having a bowel movement easier. Bulk-forming laxatives can be safely used long-term and are effective for treating both diarrhea and constipation. Benefiber, a more soluble fiber, tends to cause less bloating and extension.
  • Emollient laxatives. Emollients are a type of laxative also known as a “stool softener. This type of medication works by helping the body pull more fat and water into the stool, which helps makes the stool softer and easier to pass.
  • Lubricant laxatives. One example of a lubricant laxative would be mineral oil. Lubricants are oily and they work by coating the stool, making it difficult for water to be withdrawn. The stool holds on to more water, and this extra water helps to keep it soft and it is easier to pass as a bowel movement.
  • Hyperosmotic laxatives. This type of laxative includes milk of magnesia or Epsom salts. They aid in easing constipation by causing more water to be drawn into the intestine. The extra water keeps the stool soft, avoiding constipation and making it easier to pass.
  • Stimulant laxatives. Stimulants, such as castor oil, work by speeding up the movement of the muscles in the intestines to pass the waste material through. This movement, which is the muscles contracting in order to propel food on its way through the digestive tract, is called peristalsis. When peristalsis is sped up, stool is passed through the body at a faster than normal rate, which helps to prevent it from becoming thicker and causing constipation.
  • Natural laxatives. There are foods that tend to have mild laxative properties, such as prunes. Other foods that may help relieve constipation include prune juice, figs, licorice, rhubarb, and other foods that are high in fiber. The high fiber content tends to act like a bulk-forming laxative, helping to soften the stool. Eating typical serving sizes of foods that are natural laxatives is not going to have a harsh effect on the body, and are not going to cause harm to the intestines.

Laxatives Before Medical Procedures

Laxatives may also be given to clean the bowel in preparation for a test, such as colonoscopy, or before surgery. These types of laxatives are typically used under the care of a physician. These laxatives may include any of the above listed medical laxatives, and sometimes more than one form.

Also Known As: purgative

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