Understanding Laxatives

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Laxatives are commonly used medications used to treat occasional constipation. They are available over the counter (OTC) and based on how they work, they can be categorized into osmotic agents, stimulants, bulk-forming agents and stool softeners.


Agents such as polyethylene glycol (PEG), lactulose and magnesium hydroxide are water-loving substances that attract and retain water in the colon to ease and enhance stool passage. Of these agents, polyethylene glycol, which is found in MiraLAX®, has the best clinical evidence to increase stool frequency and softness in individuals with constipation. It works naturally with the water in your body to hydrate and soften, unblocking your system without causing harsh gastrointestinal side effects. MiraLAX® is highly recommended by physicians, pharmacists and gastroenterologists.


This type of laxative makes your body go by forcefully and directly stimulating the nerves in your colon. This causes the muscles of the intestinal wall to contract and help to push stool along. This action, while effective for relieving occasional constipation, may in some cases cause harsh side effects such as cramping and sudden urgency. Senna and bisacodyl are the most commonly used stimulant laxatives and are found in brands such as Senokot®, ex-lax®,
and Dulcolax®.


Bulk-forming agents are fiber supplements that trap water in the stool to increase stool weight and improve stool consistency. Commercially available fiber supplements include psyllium and bran. They may be appropriate for people who do not consume enough fiber in their diet. Some powder fiber supplements can be gritty and viscous when mixed into a beverage, and some people may find them distasteful. Once in the digestive system, common side effects include gas and bloating which comes from partial fermentation of the dietary fiber. Adequate fluid intake is necessary for bulk-forming agents to work; lack of water may enhance bloating. Bulk-forming brands include Benefiber® and Metamucil®.


As the name implies, stool softeners such as docusate sodium moisten and soften stool, making it easier to pass. Although they may work well for people with hard stools, the overall quality of evidence for constipation relief is poor — hence the recommendation for use of docusate sodium is only moderate. Stool softener brands include Colace®


Jin J. JAMA. 2014;312:1167. Leung L et al. JAFBM. 2011;24:436-451. QuintilesIMS Survey 2018, Pharmacy Times Survey 2018, QuintilesIMS Survey 2018, Accessed September 14, 2017. DiPalma JA et al. South Med J. 2007;100:1085-1090. Cleveland MV et al. South Med J. 2001;94:478-481. DiPalma JA et al. Online J Dig Health. 1999;1:1-10.


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