Agents that relax and loosen the bowels and stools
Glycerin suppositories used as laxatives.
Laxatives, purgatives, or aperients are substances that loosen stools[1] 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, and may be administered orally or rectally.
Emollient laxatives, also known as stool softeners, are anionic surfactants that enable additional water and fats to be incorporated in the stool, making movement through the bowels easier.
Emollient agents prevent constipation rather than treating long-term constipation.[3]
Lubricant agents
Lubricant laxatives are substances that coat the stool with slippery lipids and decrease colonic absorption of water so the stool slides through the colon more easily. Lubricant laxatives also increase the weight of stool and decrease intestinal transit time.[9]
Mineral oils, such as liquid paraffin, are generally the only nonprescription lubricant laxative available, but due to the risk of lipid pneumonia resulting from accidental aspiration, mineral oil is not recommended, especially in children and infants.[10][11] Mineral oil may decrease the absorption of fat-soluble vitamins and some minerals.[9]
Hyperosmotic agents
Hyperosmotic laxatives cause the intestines to hold more water, creating an osmotic gradient, which adds more pressure and stimulates bowel movement.[12][10]
Properties
Site of action: colon
Onset of action: 12–72 hours (oral), 0.25–1 hour (rectal)
Lactulose works by the osmotic effect, which retains water in the colon; lowering the pH through bacterial fermentation to lactic, formic, and acetic acids; and increasing colonic peristalsis. Lactulose is also indicated in portal-systemic encephalopathy. Glycerin suppositories work mostly by hyperosmotic action, but the sodium stearate in the preparation also causes local irritation to the colon.[citation needed]
Saline laxatives are nonabsorbable, osmotically active substances that attract and retain water in the intestinal lumen, increasing intraluminal pressure that mechanically stimulates evacuation of the bowel. Magnesium-containing agents also cause the release of cholecystokinin, which increases intestinal motility and fluid secretion.[3] Saline laxatives may alter a patient's fluid and electrolyte balance.
Properties
Site of action: small and large intestines
Onset of action: 0.5–3 hours (oral), 2–15 minutes (rectal)
Stimulant laxatives are substances that act on the intestinal mucosa or nerve plexus, altering water and electrolyte secretion.[13] They also stimulate peristaltic action and can be dangerous under certain circumstances.[14]
Prolonged use of stimulant laxatives can create drug dependence by damaging the colon's haustral folds, making users less able to move feces through their colon on their own. A study of patients with chronic constipation found that 28% of chronic stimulant laxative users lost haustral folds over the course of one year, while none of the control group did.[15]
Miscellaneous
Castor oil is a glyceride that is hydrolyzed by pancreatic lipase to ricinoleic acid, which produces laxative action by an unknown mechanism.
Properties
Site of action: colon, small intestine (see below) [citation needed]
Long-term use of castor oil may result in loss of fluid, electrolytes, and nutrients.[3]
Serotonin agonist
These are motility stimulants that work through activation of 5-HT4 receptors of the enteric nervous system in the gastrointestinal tract. However, some have been discontinued or restricted due to potentially harmful cardiovascular side effects.
Tegaserod (brand name Zelnorm) was removed from the general U.S. and Canadian markets in 2007, due to reports of increased risks of heart attack or stroke. It is still available to physicians for patients in emergency situations that are life-threatening or require hospitalization.[16]
Prucalopride (brand name Resolor) is a current drug approved for use in the EU since October 15, 2009,[17] in Canada (brand name Resotran) since December 7, 2011,[18] and in the United States since December 2018.
Chloride channel activators
Lubiprostone is used in the management of chronic idiopathic constipation and irritable bowel syndrome. It causes the intestines to produce a chloride-rich fluid secretion that softens the stool, increases motility, and promotes spontaneous bowel movements.
For adults, a randomized controlled trial found PEG (MiraLax or GlycoLax) 17 grams once per day to be superior to tegaserod at 6 mg twice per day.[21] A randomized controlled trial found greater improvement from two sachets (26 g) of PEG versus two sachets (20 g) of lactulose.[22] 17 g per day of PEG has been effective and safe in a randomized, controlled trial for six months.[23] Another randomized, controlled trial found no difference between sorbitol and lactulose.[24]
For children, PEG was found to be more effective than lactulose.[25]
Although some patients with eating disorders such as anorexia nervosa and bulimia nervosa abuse laxatives in an attempt to lose weight, laxatives act to speed up the transit of feces through the large intestine, which occurs after the absorption of nutrients in the small intestine is already complete. Thus, studies of laxative abuse have found that effects on body weight reflect primarily temporary losses of body water rather than energy (calorie) loss.[26][31][32]
Laxative gut
Physicians warn against the chronic use of stimulant laxatives due to concern that chronic use could cause the colonic tissues to get worn out over time and not be able to expel feces due to long-term overstimulation.[33] A common finding in patients having used stimulant laxatives is a brown pigment deposited in the intestinal tissue, known as melanosis coli.[citation needed]
^ abcdef"Constipation"(PDF). www.digestive.niddk.nih.gov. National Digestive Diseases Information Clearinghouse. Retrieved 3 November 2014.
^Bulk-forming agent entry in the public domain NCI Dictionary of Cancer Terms
^ abcdefghBerardi M, Tietze KJ, Shimp LA, Rollins CJ, Popovich NG (2006). Handbook of Nonprescription Drugs (15th ed.). Washington, D.C.: American Pharmaceutical Association. ISBN978-1582120744.
^ abc"The Facts About Fiber"(PDF). www.aicr.org. American Institute for Cancer Research. Archived from the original(PDF) on 3 November 2014. Retrieved 3 November 2014.
^Stacewicz-Sapuntzakis M, Bowen PE, Hussain EA, Damayanti-Wood BI, Farnsworth NR (2001). "Chemical composition and potential health effects of prunes: a functional food?". Critical Reviews in Food Science and Nutrition. 41 (4): 251–86. doi:10.1080/20014091091814. PMID11401245. S2CID31159565.
^ abcBerardi M, Tietze KJ, Shimp LA, Rollins CJ, Popovich NG (2006). Handbook of Nonprescription Drugs (15th ed.). Washington, D.C.: American Pharmaceutical Association. ISBN978-1582120744.
^Dipalma JA, Cleveland MV, McGowan J, Herrera JL (2007). "A randomized, multicenter, placebo-controlled trial of polyethylene glycol laxative for chronic treatment of chronic constipation". Am. J. Gastroenterol. 102 (7): 1436–41. doi:10.1111/j.1572-0241.2007.01199.x. PMID17403074. S2CID10946562.
^Lederle FA, Busch DL, Mattox KM, West MJ, Aske DM (1990). "Cost-effective treatment of constipation in the elderly: a randomized double-blind comparison of sorbitol and lactulose". Am J Med. 89 (5): 597–601. doi:10.1016/0002-9343(90)90177-F. PMID2122724.
^Brown NW, Treasure JL, Campbell IC (2001). "Evidence for long-term pancreatic damage caused by laxative abuse in subjects recovered from anorexia nervosa". International Journal of Eating Disorders. 29 (2): 236–238. doi:10.1002/1098-108X(200103)29:2<236::AID-EAT1014>3.0.CO;2-G. PMID11429987.
^Oster JR, Materson BJ, Rogers AI (November 1980). "Laxative abuse syndrome". Am. J. Gastroenterol. 74 (5): 451–8. PMID7234824.
^Lacey JH, Gibson E (1985). "Controlling weight by purgation and vomiting: A comparative study of bulimics". Journal of Psychiatric Research. 19 (2–3): 337–341. doi:10.1016/0022-3956(85)90037-8. PMID3862833.
^Joo JS, Ehrenpreis ED, Gonzalez L, Kaye M, Breno S, Wexner SD, Zaitman D, Secrest K (June 1998). "Alterations in colonic anatomy induced by chronic stimulant laxatives: the cathartic colon revisited". Journal of Clinical Gastroenterology. 26 (4): 283–6. doi:10.1097/00004836-199806000-00014. PMID9649012.
^Stolberg, Michael (2003). "[The miraculous effects of taking laxatives. Success and failure of pre-modern medical treatment from the patients' perspective]". Wurzburger Medizinhistorische Mitteilungen. 22: 167–177. ISSN0177-5227. PMID15641192.
