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Laxatives, purgatives, or aperients are substances that loosen stools<ref name=NIDDK>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.
TypesEdit
Bulk-forming agentsEdit
Bulk-forming laxatives, also known as roughage, are substances, such as fiber in food and hydrophilic agents in over-the-counter drugs, that add bulk and water to stools so they can pass more easily through the intestines (lower part of the digestive tract).<ref>Bulk-forming agent entry in the public domain NCI Dictionary of Cancer Terms</ref>
Properties
- Site of action: small and large intestines
- Onset of action: 12–72 hours
- Examples: dietary fiber, Metamucil, Citrucel, FiberCon<ref name=Handbook>Template:Cite book</ref>
Bulk-forming agents generally have the gentlest of effects among laxatives,<ref name=NIDDK/> making them ideal for long-term maintenance of regular bowel movements.
Dietary fiberEdit
Foods that help with laxation include fiber-rich foods. Dietary fiber includes insoluble fiber and soluble fiber, such as:<ref name=AICR>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
- Fruits, such as bananas,<ref>Template:Cite journal</ref> though this depends on their ripeness,<ref>Template:Cite news</ref> kiwifruits,<ref name=pmid12074185>Template:Cite journal</ref> prunes,<ref>Template:Cite journal</ref> apples (with skin), pears (with skin), and raspberries<ref name=NIDDK/>
- Vegetables, such as broccoli, string beans, kale, spinach,<ref name=AICR/> cooked winter squash, cooked taro and poi, cooked peas, and baked potatoes (with skin)<ref name=NIDDK/>
- Whole grains
- Bran products<ref name=NIDDK/><ref name=AICR/>
- Nuts
- Legumes, such as beans, peas, and lentils<ref name=NIDDK/>
Emollient agents (stool softeners)Edit
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.
Properties
- Site of action: small and large intestines
- Onset of action: 12–72 hours
- Examples: Docusate (Colace, Diocto), Gibs-Eze<ref name=Handbook/>
Emollient agents prevent constipation rather than treating long-term constipation.<ref name=Handbook/>
Lubricant agentsEdit
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.<ref name="Handbook3">Template:Cite book</ref>
Properties
- Site of action: colon
- Onset of action: 6–8 hours
- Example: mineral oil<ref name="Handbook3" />
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.<ref name=":0">Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Mineral oil may decrease the absorption of fat-soluble vitamins and some minerals.<ref name="Handbook3" />
Hyperosmotic agentsEdit
Hyperosmotic laxatives cause the intestines to hold more water, creating an osmotic gradient, which adds more pressure and stimulates bowel movement.<ref name="Handbook22">Template:Cite book</ref><ref name=":0" />
Properties
- Site of action: colon
- Onset of action: 12–72 hours (oral), 0.25–1 hour (rectal)
- Examples: glycerin suppositories (Hallens), sorbitol, lactulose, and polyethylene glycol (PEG - Colyte, MiraLax)<ref name="Handbook22" />
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.Template:Cn
Solutions of polyethylene glycol and electrolytes (sodium chloride, sodium bicarbonate, potassium chloride, and sometimes sodium sulfate) are used for whole bowel irrigation, a process designed to prepare the bowel for surgery or colonoscopy and to treat certain types of poisoning. Brand names for these solutions include GoLytely, GlycoLax, Cosmocol, CoLyte, Miralax, Movicol, NuLytely, Suprep, and Fortrans. Solutions of sorbitol (SoftLax) have similar effects.Template:Cn
Saline laxative agentsEdit
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.<ref name=Handbook/> 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)
- Examples: sodium phosphate (and variants), magnesium citrate, magnesium hydroxide (milk of magnesia), and magnesium sulfate (Epsom salt)<ref name=Handbook/>
Stimulant agentsEdit
Stimulant laxatives are substances that act on the intestinal mucosa or nerve plexus, altering water and electrolyte secretion.<ref>Laxative (Oral Route) from Mayo clinic. Last updated: Nov. 1, 2012</ref> They also stimulate peristaltic action and can be dangerous under certain circumstances.<ref name=pmid9649012>Template:Cite journal</ref>
Properties
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.<ref>Template:Cite journal</ref>
MiscellaneousEdit
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) Template:Citation needed
- Onset of action: 2–6 hours
- Examples: castor oil<ref name=Handbook/>
Long-term use of castor oil may result in loss of fluid, electrolytes, and nutrients.<ref name=Handbook/>
Serotonin agonistEdit
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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Prucalopride (brand name Resolor) is a current drug approved for use in the EU since October 15, 2009,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> in Canada (brand name Resotran) since December 7, 2011,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and in the United States since December 2018.
Chloride channel activatorsEdit
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.
Comparison of available agentsEdit
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| Preparation(s) | Type | Site of action | Onset of action |
|---|---|---|---|
| Cascara (casanthranol) | Anthraquinone | colon | 6–8 hours |
| Buckthorn | Anthraquinone | colon | 6–8 hours |
| Senna extract (senna glycoside) | Anthraquinone | colon | 6–8 hours |
| Aloe vera (aloin) | Anthraquinone | colon | 8–10 hours |
| Phenolphthalein | Triphenylmethane | colon | 8 hours |
| Bisacodyl (oral) | Triphenylmethane | colon | 6–12 hours |
| Bisacodyl (suppository) | Triphenylmethane | colon | 60 minutes |
| Castor oil | Ricinoleic acid | small intestine | 2–6 hours |
EffectivenessEdit
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.<ref name="pmid17573794">Template:Cite journal</ref> A randomized controlled trial found greater improvement from two sachets (26 g) of PEG versus two sachets (20 g) of lactulose.<ref name=pmid9895382>Template:Cite journal</ref> 17 g per day of PEG has been effective and safe in a randomized, controlled trial for six months.<ref name="pmid17403074">Template:Cite journal</ref> Another randomized, controlled trial found no difference between sorbitol and lactulose.<ref name=pmid2122724>Template:Cite journal</ref>
For children, PEG was found to be more effective than lactulose.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Problems with useEdit
Laxative abuseEdit
Some of the less significant adverse effects of laxative abuse include dehydration (which causes tremors, weakness, fainting, blurred vision, kidney damage), low blood pressure, fast heart rate, postural dizziness and fainting;<ref name="Laxative abuse review" /> however, laxative abuse can lead to potentially fatal acid-base, and electrolyte imbalances.<ref name="Laxative abuse review" /> For example, severe hypokalaemia has been associated with distal renal tubular acidosis from laxative abuse.<ref name="Laxative abuse review" /> Metabolic alkalosis is the most common acid-base imbalance observed.<ref name="Laxative abuse review" /> Other significant adverse effects include rhabdomyolysis,<ref name="Laxative abuse review" /> steatorrhoea,<ref name="Laxative abuse review" /> inflammation and ulceration of colonic mucosa,<ref name="Laxative abuse review" /> pancreatitis,<ref name="Laxative abuse review" /><ref name=Brown>Template:Cite journal</ref> kidney failure,<ref name="Laxative abuse review" /><ref name=copeland>Template:Cite journal</ref><ref name=wright>Template:Cite journal</ref> factitious diarrhea<ref name="Laxative abuse review" /><ref>Template:Cite journal</ref> and other problems.<ref name="Laxative abuse review">Template:Cite journal</ref> 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 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.<ref name="Laxative abuse review" /><ref name=Lacey>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Laxative gutEdit
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.<ref>Template:Cite journal</ref> A common finding in patients having used stimulant laxatives is a brown pigment deposited in the intestinal tissue, known as melanosis coli.Template:Citation needed
Historical and health fraud usesEdit
Laxatives, once called "physicks" or "purgatives", were used extensively in historic medicine to treat many conditions for which they are now generally regarded as ineffective in evidence-based medicine.<ref>Template:Cite journal</ref> Likewise, laxatives (often termed colon cleanses) may be promoted in alternative medicine for various conditions of quackery, such as "mucoid plaque".<ref>Template:Cite book</ref>
See alsoEdit
- ATC code A06
- Bowel management
- Cathartic
- Dietary fiber
- Diuretic
- Maltitol
- Enema
- Suppository
- Transanal irrigation
ReferencesEdit
Template:Major Drug Groups Template:Laxatives Template:Irritable bowel syndrome Template:Authority control Template:Portal bar