Pharmacology - Laxatives
What are the major classifications of laxatives?
- Bulk-forming laxatives - Surfacant laxatives/stool softeners - Stimulant laxatives - Osmotic laxatives
What drug is a stimulant laxative?
bisacodyl (Dulcolax)
What drug is a surfactant laxative/stool softener
docusate sodium (Colace)
What drug is a bulk-forming laxative?
psyllium (Metamucil)
Osmotic Laxatives
- Laxative salts (magnesium and sodium) - Poorly absorbes salts that draw water into intestinal lumen; fecal mass softens and swells, wall stretches, and peristalsis is stimulated - Low doses: results in 6-12 hours - High doses: results in 2-6 hours - ex. magnesium hydroxide (MOM), also, polyethylene glycol (Miralax)
What drug is an osmotic laxative?
- Magnesium hydroxide - Milk of Magnesia (MOM)
What are the causes of laxative abuse?
- Misconception that bowel movements must occur daily - Can perpetuate their own use, now MUST take a laxative to trigger a bowel movement - Bowel replenishment after laxative-caused evacuation can be 2-5 days; often mistaken for constipation
Indications for Laxative Use
- Obtaining fresh stool sample - Before treatment/procedure preparation - ex. prep for colonoscopies and bowel surgeries - Expelling pinworms/parasites after treatment - Constipation (multiple causes, including pregnancy and opioid use) - Preventing fecal impaction in bedridden patients - Removing poisons - Preventing straining for at risk clients: recent MI, brain surgery, eye surgery, HTN
Treatment of laxative abuse
- Prevent by using the lowest dose, short-term - Try to withdraw from laxatives at the same time, increase fiber, fluids, and activity level
What is the laxative effect?
- Production of soft, formed stool over a period of 1 or more days - Relatively mild
How are laxatives used to ease or stimulate defecation?
- Soften the stool - Increase stool volume to stimulate peristalsis - Hasten fecal passage through the intestine - Facilitate evacuation from the rectum - Misuse comes from misconceptions of what constitutes normal bowel function
Surfactant Laxatives/Stool Softeners
- ex. docusate (Colace) - Softens stool: increases quantities of water in the intestinal lumen by decreasing surface tension of stool - Widely used - Mild
Adverse effects of osmotic laxatives
- Abdominal cramping - Dehydration: substantial water loss - too much drawn out of the blood into the intestines. Diarrhea may be triggered - If has renal disease: toxicity of magnesium can occur - Sodium retention: exacerbated heart failure, hypertension, edema
What are the adverse effects of bulk-forming laxatives?
- Adverse effects are minimal - N/V - Esophageal obstruction due to poor fluid intake with dose - lots of bulk with inadequate liquid intake causes a blockage - Need to drink a full glass of water with dose
What are the consequences of laxative abuse?
- Diminished defecation reflex, leading to further reliance on laxatives - Electrolyte imbalance, dehydration, and colitis
Stimulant Laxatives
- Ex. bicodyl (Dulcolax) - Two effects on bowel: stimulate intestinal motility and increase quantities of water and electrolytes in the intestinal lumen - Widely used and abused - Used for opioid-induced constipation and for constipation from slow intestinal transit/movement - Again, need to take with a full glass of water
Bulk-Forming Laxatives
- Function similarly to dietary fiber: swell with water to form a gel to soften fecal mass and increase mass to stimulate peristalsis - Preferred treatment for temporary treatment of constipation
Other Laxatives
- Glycerin suppository - Mineral oil (is not absorbed so passes through) - Both of these lubricate the GI tract to ease stool elimination
Contraindications of Laxative Use
- Individuals experiencing abdominal pain, nausea, cramps, or other symptoms of appendicitis, regional enteritis, diverticulitis, and ulcerative colitis - Fecal impaction or bowel obstruction - Habitual use/abuse - Use with caution in pregnancy and lactation
