Ch 83 Laxatives Flashcards
What is the definition of constipation?
- Infrequent, difficult, or incomplete bowel movements.
- Typically involves fewer than three bowel movements per week.
- May include hard stools, straining, or a sensation of incomplete evacuation.
What are nondrug measures to correct constipation?
- Increase dietary fiber intake (e.g., fruits, vegetables, whole grains)
- Increase fluid intake
- Engage in regular physical activity
- Establish a regular toilet routine
- Avoid delaying the urge to defecate
What are the indications for the use of a laxative?
- To relieve constipation
- To prevent straining (e.g., in cardiac or post-surgical patients)
- To empty the bowel before diagnostic procedures (e.g., colonoscopy)
- To treat drug-induced constipation (e.g., from opioids)
- To manage fecal impaction or bowel evacuation in certain conditions
What are the four major classes of laxatives and their mechanisms?
- Bulk-forming (e.g., psyllium): Absorb water, increase stool bulk, stimulate peristalsis
- Surfactant (e.g., docusate): Soften stool by allowing water/fat penetration
- Stimulant (e.g., bisacodyl, senna): Stimulate intestinal motility and increase water secretion
- Osmotic (e.g., milk of magnesia, polyethylene glycol): Draw water into the intestine, softening stool and stimulating peristalsis
Contraindications for laxative use
- abdominal pain
- nausea
- cramps
- symptoms of appendicitis
- diverticulitis
- ulcerative colitis
- acute surgical abdomen
- fecal impaction
- bowel obstruction
Use with caution in pregnancy and lactation
Drug: Psyllium (Metamucil)
Class: Bulk-forming laxative
MOA: Absorbs water, forming a gel that softens stool and increases bulk.
Note: Functions like dietary fiber; take with plenty of water.
Drug: Docusate sodium (Colace)
Class: Surfactant (stool softener)
MOA: Lowers surface tension to allow water penetration into stool.
Note: Produces soft stool after a few days of use.
Drug: Bisacodyl (Dulcolax)
Class: Stimulant laxative
MOA: Stimulates enteric nerves and increases secretion of water/electrolytes.
Note: Commonly used for opioid-induced constipation; may cause cramping.
Drug: Milk of Magnesia
Class: Osmotic laxative
MOA: Pulls water into intestines, promoting peristalsis.
Note: High doses work within hours; may cause dehydration.
Drug: Glycerin suppository
Class: Osmotic laxative
MOA: Softens/lubricates stool and stimulates rectal contraction.
Note: Often used in children; works within 30 minutes.
Useful for reestablishing normal bowel function after termination of chronic laxative use
Drug: mineral oil
Class: lubricant laxative
MOA: coats the surface of stool and intestinal mucosa with a waterproof film which retains water, making it softer and easier to pass
Note: can cause lipid pneumonia, anal leakage, and deposition of mineral oil in the liver
Bowel cleansing products used for colonoscopy preparation
- Polyethylene Glycol (PEG)–Based Products
* GoLYTELY & Colyte - 4L; ingest 300mL every 10min
* HalfLYTELY & MoviPrep - 2L - Sodium Phosphate–Based Products (⚠️ used less often due to kidney/electrolyte risks)
