The Four Types of Laxatives: How Each Works and the Risks they Pose

Is there anyone reading this article who hasn’t been constipated at one time or another? Symptoms can range from feeling bloated to stomach cramps, but for many people the solution is the same: laxatives. The next time you reach for one, however, bear in mind that laxatives aren’t without risks, and overusing them can make your bowels "lazy" and cause rebound constipation. In many cases, all you may need to become "regular" again is more water and fiber.

Do you really need a laxative? If you’re constipated, a laxative isn’t necessarily the best medicine. But if you do need a laxative in the short term, some over-the-counter types are much safer than others. However, using any laxative – except fiber supplements – long term can pose a variety of health problems. Doctors say that laxatives can cause a dangerous upset of body fluids and electrolytes (minerals that help maintain body chemistry), muscle weakness, and heart-rhythm abnormalities. Chronic use can even damage your colon. And once you stop using laxatives, rebound constipation can occur, creating long-term bowel difficulties.

Know that not all laxatives are created equal. Some are gentler than others. Medical experts say that the ingredients that can be extremely harsh include phenolphthalein, bisacodyl, castor oil, senna, and cascara sagrada. Here are the four types of laxatives, how they work, what their possible side effects are, and how each of them should be taken as per the guidelines set by medical experts:

1. Fiber products / bulk-forming agents – These laxatives make stool larger, which helps the intestines contract and provoke a bowel movement. They are slow-acting and work from 12 hours up to three days; best to build up gradually over 7 to 10 days. Doctors recommend daily dosage and, as a fiber supplement, may be used long term, if necessary. Users must drink lots of fluids, particularly water or fruit juice. Possible side effects include bloating, abdominal pain, and gas; intestinal blockage; rare allergic reactions; breathing and swallowing difficulty; and skin rash or itching.

2. Osmotic agents and saline laxatives – These laxatives pull water into the large intestine, creating bulk and pressure to stimulate contractions. The Lactulose brand works from 24 to 48 hours, while saline works from half an hour to 3 hours. Osmotics can cause dehydration and the buildup of magnesium and phosphate, which is dangerous for anyone with kidney problems. Doctors recommend short-term use; no more than three consecutive days. And to avoid problems, take each dose with 8 to 16 ounces (235 to 470 milliliters) of water. Possible side effects include dizziness, confusion, fatigue, muscle cramps, and irregular heartbeat which can indicate an electrolyte imbalance.

3. Stool softeners and lubricants – These laxatives allow fluids to mix into the stool, making it easier to pass. Lubricants also coat the stool and bowel wall with a water-resistant film. These laxatives work at an average speed of from one to two days, but can take as long as five days. Liquid stool softeners may be mixed with milk or fruit juices; mineral oil should not be taken within two hours of a meal. Stool softeners do not cause a bowel movement, but they may help prevent constipation. Doctors prescribe short-term use of softeners, and occasional use only of mineral oil. Possible side effects include skin rash, risk of cramping, and throat irritation (liquid form only). Mineral oil can also build up in the body, causing health problems, and may cause leakage from the rectum.

4. Stimulant laxatives – These laxatives contain an irritant, such as bisacodyl, that stimulates the lining of the bowel, causing increased contractions. Liquid or pill yields semi-solid bowel movement in 6 to 8 hours, while suppositories work in 15 minutes to 1 hour. Overuse of these laxatives can cause serious intestinal damage and "lazy bowel syndrome," in which the bowel can’t function without a laxative. Bisacodyl tablets should not be crushed or chewed or taken with milk or antacids. Doctors recommend short-term use only – no more than three consecutive days. Possible side effects include muscle cramps, discolored urine or stools (red, violet, or pink), allergic reactions (such as skin rash), fatigue, and irregular heartbeat which can indicate an electrolyte imbalance.

As a final reminder, never use a laxative to facilitate weight loss. Laxatives do not stop calories from being absorbed, and they can cause physical dependence and serious or even deadly changes in metabolism.