Laxative

Laxatives (purgatives, aperients) are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under certain circumstances. Sufficiently high doses of laxatives cause diarrhea. Laxatives work to increase the movement of fecal matter along the colon.

Some laxatives combine more than one active ingredient to produce a combination of the effects. Laxatives may be oral or in suppository form.

Foods

Some foods can be eaten to cure constipation and act as laxatives, although the effectiveness may vary. These include:

• Almonds
• Aloe vera
• Apple juice
• Apricots
• Basil
• Beets
• Banana
• Cactus fruit
• Carob
• Capsicum
• Celery
• Chicory
• Coconut
• Coffee
• Dandelion
• Dates
• Endive
• Fenugreek
• Flaxseed
• Grapes
• Guava (with seeds for full effect)
• Jujube
• Kale
• Kiwifruit
• Liquorice
• Mango
• Mint
• Molasses
• Olive oil
• Orange juice
• Papaya
• Parsley
• Peach
• Pear
• Persimmon
• Pineapple
• Plum
• Prune and prune juice
• Rhubarb
• Senna (genus)
• Soybean
• Tamarind
• Tea
• Tomato juice
• Vanilla
• Walnut
• Watercress
• Yam

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Bulk-producing agents

• Site of Action: Small and large intestine
• Onset of Action: 12–72 hours
• Examples: Bran, Gamkaraya, Sterculia[Normacol], psyllium husk (Metamucil), methylcellulose (Citrucel), polycarbophil, dietary fibre, apples, broccoli, prunes.

Also known as bulking agents or roughage, these include dietary fibre. Bulk-producing agents cause the stool to be bulkier and to retain more water, as well as forming an emollient gel, making it easier for peristaltic action to move it along. They should be taken with plenty of water. Bulk-producing agents have the gentlest of effects among laxatives and can be taken just for maintaining regular bowel movements.

Stool softeners

• Site of Action: Small and large intestine
• Onset of Action: 12–72 hours
• Examples: docusate (Colace, Diocto)

These enable additional water and fats to be incorporated in the stool, making it easier to move.

Lubricants or emollient

• Site of Action: Colon
• Onset of Action: 6–8 hours

These simply make the stool slippery, so that it slides through the intestine more easily. An example is mineral oil, which also retards colonic absorption of water, softening the stool. Mineral oil may decrease the absorption of fat-soluble vitamins and some minerals.

Hydrating agents (osmotics)

These cause the intestines to hold more water within, softening the stool. There are two principal types, saline and hyperosmotic.

Saline

• Site of Action: Small and large intestine
• Onset of Action: 0.5–6 hours
• Examples: sodium phosphate (and variants), potassium sodium tartrarate, magnesium citrate, magnesium hydroxide (Milk of magnesia or Cream of magnesia), magnesium sulfate (which is Epsom salt).

Saline laxatives attract and retain water in the intestinal lumen, increasing intraluminal pressure and thus softening the stool. They also cause the release of cholecystokinin, which stimulates the digestion of fat and protein. Saline laxatives may alter a patient's fluid and electrolyte balance.

Hyperosmotic agents

• Site of Action: Colon
• Onset of Action: 0.5–3 hours
• Examples: Glycerin suppositories, sorbitol, lactulose, and polyethylene glycol (PEG).

Lactulose works by the osmotic effect, which retains water in the colon, lowering the pH through bacterial fermentation to lactic, formic and acetic acid, and increasing colonic peristalsis. Lactulose is also indicated in Portal-systemic encephalopathy. Glycerin suppositories work mostly by hyperosmotic action, but also the sodium stearate in the preparation causes local irritation to the colon.

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, CoLyte, Miralax, NuLytely, and others.

Effectiveness

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. A randomized controlled trial found greater improvement from 2 sachets (26 grams) of PEG versus 2 sachets (20 grams) of lactulose. 17 grams/day of PEG has been effective and safe in a randomized controlled trial for six months. Another randomized controlled trial found no difference between sorbitol and lactulose.

For children, PEG was found to be more effective than lactulose.

Stimulant or irritant

Stimulant laxatives act on the intestinal mucosa or nerve plexus, altering water and electrolyte secretion. They also stimulate peristaltic action and can be dangerous under certain circumstances. They are the most severe among laxatives and should be used with care.

Common Stimulant Laxatives

Preparation(s)	Type	Site of Action	Onset of
Cascara (casanthranol)	Anthraquinone	colon	36–8 hours
Buckthorn	Anthraquinone	colon	36–8 hours
Senna extract (senokot)	Anthraquinone	colon	36–8 hours
Aloe vera (aloin)	Anthraquinone	colon	58–10 hours
Phenolphthalein	Triphenylmethane	colon	48 hours
Dulcolax (bisacodyl) (PO)	Triphenylmethane	colon	66–12 hours
Dulcolax (bisacodyl) (suppository)	Triphenylmethane	colon	160 minutes
Microlax	enema	rectum and colon	015–60 minutes
Castor Oil	ricinoleic acid	small intestine	22–6 hours

Serotonin agonist

Tegaserod is a motility stimulant that works through activation of 5-HT₄ receptors of the enteric nervous system in the gastrointestinal tract. However caution must be taken due to potentially harmful cardiovascular side-effects.

Zelnorm (market name for Tegaserod) was discontinued from marketing in the United States on March 30, 2007 but is still available for prescription under tight controls.

Uses

• Bowel preparation
• Chronic constipation
• Chronic immobility

Problems with use

Laxative abuse

Laxative abuse is potentially serious since it can lead to intestinal paralysis, irritable bowel syndrome (IBS), pancreatitis, renal failure, and other problems, even though recovery is possible with proper treatment.

Laxative gut

Physicians warn against the chronic use of stimulant laxatives due to concern that chronic use causes the colonic tissues to get worn out over time and not be able to expel feces due to long term overstimulation. It is unclear whether the elongated and poorly moving colon of a patient with chronic constipation was a result of or was just a cause for patients' use of stimulant laxatives. A common finding in patients who have used stimulant laxatives is a brown pigment deposited in the intestinal tissue, known as melanosis coli.

Eating disorders

Laxatives are used by people with an eating disorder. In cases of bulimia nervosa the patient abuses laxatives to get rid of calories, to purge food in the intestines before it becomes digested and absorbed by the body. This will not work, because laxatives hasten the elimination of undigested remains of food in the large intestine and colon. The large intestine and colon do not digest food. They just collect the undigested remains and hold it and absorb water until it is defaecated. Weight loss may be felt, but this is only temporary due to the fact that the person has expelled much of the fluids from their body. The common question of whether or not chronic diarrhea associated with laxative use can promote some degree of true weight loss remains unknown. In any case, this type of laxative misuse causes water to be lost more rapidly than is healthy, potentially leading to dehydration and electrolyte imbalance. Prolonged usage of laxatives will actually cause constipation. The sensation of bloating can be significant due to excessive water retention, leading to people with eating disorders to increase the dosage of the laxatives, resulting in dependency and further complicating the constipation. Abusing stimulant-type laxatives can lead to permanent impairment of the bowels, and the constipation problem becomes irreversible. In addition, blood can develop in stools, and excessive blood loss can result in anemia. Patients recovering from laxative abuse often have several months of problematic water retention, resulting in temporary weight gain (not noticeable on the exterior), and sometimes "pitting" edema (in which pressing on the skin leaves an indentation).

See also

• ATC code A06
• Cathartic

External links

• Laxative overdose – MedlinePlus.
• [1]
• Senna tea benefits, problems as a laxative.
• [2] bulk-forming agents.