Laxatives,purgatives, oraperients are substances that loosenstools[1] and increasebowel movements. They are used to treat and preventconstipation.
Laxatives vary as to how they work and the side effects they may have. Certainstimulant,lubricant, andsaline laxatives are used to evacuate thecolon forrectal and bowel examinations, and may be supplemented byenemas under certain circumstances. Sufficiently high doses of laxatives may causediarrhea. Some laxatives combine more than one active ingredient, and may be administeredorally orrectally.
Bulk-forming laxatives, also known asroughage, are substances, such asfiber in food andhydrophilic agents inover-the-counter drugs, that add bulk and water tostools so they can pass more easily through theintestines (lower part of thedigestive tract).[2]
Properties
Bulk-forming agents generally have the gentlest of effects among laxatives,[1] making them ideal for long-term maintenance of regular bowel movements.
Foods that help with laxation include fiber-rich foods.Dietary fiber includesinsoluble fiber andsoluble fiber, such as:[4]
Emollient laxatives, also known as stool softeners, areanionic surfactants that enable additional water and fats to be incorporated in the stool, making movement through the bowels easier.
Properties
Emollient agents prevent constipation rather than treating long-term constipation.[3]
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]
Properties
Mineral oils, such asliquid 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 laxatives cause the intestines to hold more water, creating anosmotic gradient, which adds more pressure and stimulates bowel movement.[12][10]
Properties
Lactulose works by theosmotic effect, which retains water in the colon; lowering thepH through bacterial fermentation to lactic, formic, and acetic acids; and increasing colonicperistalsis. Lactulose is also indicated inportal-systemic encephalopathy. Glycerin suppositories work mostly by hyperosmotic action, but thesodium stearate in the preparation also causes local irritation to the colon.[citation needed]
Solutions ofpolyethylene glycol and electrolytes (sodium chloride,sodium bicarbonate,potassium chloride, and sometimessodium sulfate) are used forwhole bowel irrigation, a process designed to prepare the bowel for surgery orcolonoscopy and to treat certain types ofpoisoning. Brand names for these solutions include GoLytely, GlycoLax, Cosmocol, CoLyte, Miralax, Movicol, NuLytely, Suprep, and Fortrans. Solutions ofsorbitol (SoftLax) have similar effects.[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 ofcholecystokinin, which increases intestinal motility and fluid secretion.[3] Saline laxatives may alter a patient's fluid and electrolyte balance.
Properties
Stimulant laxatives are substances that act on the intestinalmucosa ornerve plexus, altering water andelectrolyte secretion.[13] They also stimulate peristaltic action and can be dangerous under certain circumstances.[14]
Properties
Prolonged use of stimulant laxatives can create drug dependence by damaging the colon'shaustral 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]
Castor oil is a glyceride that is hydrolyzed by pancreatic lipase toricinoleic acid, which produces laxative action by an unknown mechanism.
Properties
Long-term use of castor oil may result in loss of fluid, electrolytes, and nutrients.[3]
These are motility stimulants that work through activation of5-HT4 receptors of theenteric nervous system in thegastrointestinal tract. However, some have been discontinued or restricted due to potentially harmful cardiovascular side effects.
Tegaserod (brand nameZelnorm) 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.
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.
| Preparation(s) | Type | Site of action | Onset of action |
|---|---|---|---|
| Cascara (casanthranol) | Anthraquinone | colon | 36–8 hours |
| Buckthorn | Anthraquinone | colon | 36–8 hours |
| Senna extract (senna glycoside) | Anthraquinone | colon | 36–8 hours |
| Aloe vera (aloin) | Anthraquinone | colon | 58–10 hours |
| Phenolphthalein | Triphenylmethane | colon | 48 hours |
| Bisacodyl (oral) | Triphenylmethane | colon | 66–12 hours |
| Bisacodyl (suppository) | Triphenylmethane | colon | 160 minutes |
| Castor oil | Ricinoleic acid | small intestine | 22–6 hours |
For adults, arandomized controlled trial foundPEG (MiraLax or GlycoLax) 17 grams once per day to be superior totegaserod 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]
Some of the less significant adverse effects of laxative abuse includedehydration (which causes tremors, weakness, fainting, blurred vision, kidney damage),low blood pressure,fast heart rate, postural dizziness andfainting;[26] however, laxative abuse can lead to potentially fatalacid-base, andelectrolyte imbalances.[26] For example, severehypokalaemia has been associated withdistal renal tubular acidosis from laxative abuse.[26]Metabolic alkalosis is the most common acid-base imbalance observed.[26] Other significant adverse effects includerhabdomyolysis,[26]steatorrhoea,[26]inflammation andulceration of colonic mucosa,[26]pancreatitis,[26][27]kidney failure,[26][28][29]factitious diarrhea[26][30] and other problems.[26] The colon will need more quantities of laxatives to keep functioning, this will result in a lazy colon, infections, irritable bowel syndrome, and potential liver damage.
Although some patients with eating disorders such asanorexia nervosa andbulimia 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]
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 asmelanosis coli.[citation needed]
Laxatives, once called "physicks" or "purgatives", were used extensively inhistoric medicine to treat many conditions for which they are now generally regarded as ineffective inevidence-based medicine.[34] Likewise, laxatives (often termedcolon cleanses) may be promoted inalternative medicine for various conditions ofquackery, such as "mucoid plaque".[35]
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