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*Laxatives

.

*Constipation

*Abnormally infrequent and difficult passage of feces through the lower GI tract

*Symptom, not a disease

*Disorder of movement through the colon and/or rectum

*Can be caused by a variety of diseases or drugs

*What is constipation?

*Constipation is generally defined as infrequent and/or unsatisfactory defecation fewer than 3 times per week.

*Patients may define constipation as passing hard stools or straining, incomplete or painful defecation.

Epidemiology

2-27% of the population has constipation

Constipation affects twice as many women as men

Constipation is more prevalent in non-White persons than in White persons (non-White:White ratio range 1.11--2.89)

Causes of constipation Diet

Lack of exercise

Age

Irregular bowel habits

Drug induced

Disease States/Conditions

Spasam of sigmoid colon

Dysfunction of myenteric plexus

I’m constipated, now what?

Two approaches to consider:

Non-drug Approach Drug Approach

*1. Exercise - Fibre in the diet - Fluid Intake

No evidence that increased exercise is beneficial

in severe constipation

Aim for 25-30g fibre/day

Unless dehydrated, increasing fluid does not

relieve chronic constipation and may increase

the risk of fluid overload eg heart or renal failure

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*Laxatives: Mechanism of

Action

*Bulk forming

*Emollient

*Hyperosmotic

*Saline

*Stimulant

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*Laxatives: Mechanism of

Action (cont'd)

1. Bulk forming

*High fiber

*Absorbs water to increase bulk

*Distends bowel to initiate reflex bowel activity

Examples:

*psyllium (Metamucil)

*methylcellulose (Citrucel)

*polycarbophil

Improve stool consistency and frequency with

regular use

Ensure good fluid intake to prevent faecal

impaction

Onset of action 2-3 days

Side Effects may include bloating,

flatulence, distension

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*Laxatives: Mechanism of

Action (cont'd)

2. Emollient

*Stool softeners and lubricants

*Promote more water and fat in the stools

*Lubricate the fecal material and intestinal walls

Examples:

*Stool softeners: docusate salts (Colace, Surfak)

*Lubricants: mineral oil

*Stool softener may take days to become effective.

*They should not be taken together with mineral oil because of the potential for absorption of the mineral oil.

*Lubricant laxatives include Mineral oil and glycerin suppositories.

* They facilitate the passage of hard stools.

*Mineral oil should be taken orally in an upright position to avoid its aspiration and potential for lipid or lipoid pneumonia.

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*Laxatives: Mechanism of

Action (cont'd)

3. Hyperosmotic

*Increase fecal water content

*Result: bowel distention, increased peristalsis, and evacuation

Examples:

*polyethylene glycol (GoLYTELY)

*sorbitol

*glycerin

*lactulose (Chronulac)

*PEG powder for solution is available as a prescription and also an over-the-counter laxative.

*Lactulose is a semisynthetic disaccharide sugar that also acts as an osmotic laxative. It is a product that cannot be hydrolyzed by intestinal enzymes. Oral doses are degraded in the colon by colonic bacteria into lactic, formic, and acetic acids. This increases osmotic pressure, thereby accumulating fluid, distending the colon, creating a soft stool, and causing defecation.

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*Laxatives: Mechanism of

Action (cont'd)

Saline

*Increase osmotic pressure within the intestinal tract, causing more water to enter the intestines

*Result: bowel distention, increased peristalsis, and evacuation

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*Laxatives: Mechanism of

Action (cont'd)

Saline laxative; saline cathartic; examples:

*magnesium sulfate (Epsom salts)

*magnesium hydroxide (MOM)

*magnesium citrate

*sodium phosphate (Fleet Phospho-Soda, Fleet enema)

*Saline cathartics are nonabsorbable salts (anions and cations) that hold water in the intestine by osmosis and distend the bowel.

*increasing intestinal activity and producing defecation in a few hours.

*Electrolyte solutions containing polyethylene glycol (PEG) are used as colonic lavage solutions to prepare the gut for radiologic or endoscopic procedures.

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*Laxatives: Mechanism of

Action (cont'd)

4. Stimulant

*Increases peristalsis via intestinal nerve stimulation

Examples:

*castor oil

*senna

*cascara

*bisacodyl

*Senna is a widely used stimulant laxative.

* Its active ingredient is a group of sennosides, a natural complex of anthraquinone glycosides.

*Taken orally, it causes evacuation of the bowels within 8 to 10 hours.

*It also causes water and electrolyte secretion into the bowel.

*In combination products with a docusate-containing stool softener, it is useful in treating opioid-induced constipation.

*Bisacodyl, available as suppositories and enteric-coated tablets, is a potent stimulant of the colon.

*It acts directly on nerve fibers in the mucosa of the colon.

*Adverse effects include abdominal cramps and the potential for atonic colon with prolonged use.

*.

*Antacids should not be taken at the same time as the enteric-coated tablets. The antacid would cause the enteric coating to dissolve prematurely in the stomach, resulting in stomach irritation and pain.

*The same adverse effects could be expected with milk, H2-receptor antagonists, and PPIs

*Castor oil is broken down in the small intestine to ricinoleic acid, which is very irritating to the gut, and promptly increases peristalsis.

*It should be avoided by pregnant patients, because it may stimulate uterine contractions.

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*Laxatives: Side Effects

*Bulk forming

*Impaction

*Fluid overload

*Emollient

*Skin rashes

*Decreased absorption of vitamins

*Hyperosmotic

*Abdominal bloating

*Rectal irritation

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*Laxatives: Side Effects (cont'd)

* Saline

*Magnesium toxicity (with renal insufficiency)

*Cramping

*Diarrhea

*Increased thirst* Stimulant

*Nutrient malabsorption

*Skin rashes

*Gastric irritation

*Rectal irritation

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*Laxatives: Side Effects (cont'd)

*All laxatives can cause electrolyte imbalances!

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*Laxatives: use

*Obtain a thorough history of presenting symptoms, elimination patterns, and allergies

*Assess fluid and electrolytes before initiating therapy

*Patients should not take a laxative or cathartic if they are experiencing nausea, vomiting, and/or abdominal pain

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*Laxatives: use

*A healthy, high-fiber diet and increased fluid intake should be encouraged as an alternative to laxative use

*Long-term use of laxatives often results in decreased bowel tone and may lead to dependency

*All laxative tablets should be swallowed whole, not crushed or chewed, especially if enteric coated

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*Laxatives: use

*Patients should take all laxative tablets with 6 to 8 ounces of water

*Patients should take bulk-forming laxatives as directed by the manufacturer with at least 240 mL (8 ounces) of water

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*Laxatives: Nursing

Implications

*Bisacodyl and cascara sagrada should be given with water due to interactions with milk, antacids, and H2 blockers

*Patients should contact their physician if they experience severe abdominal pain, muscle weakness, cramps, and/or dizziness, which may indicate possible fluid or electrolyte loss

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*Laxatives: use

*Monitor for therapeutic effect