Constipation

Question 1

Bulking Laxative (solid waste)
Dietary Fiber
Psyllium

Answer 1

Increase in stool weight

• causes retention of fluid in stool
• stimulates peristalsis
• effective within 12-24-max effect several days
• REQUIRES FLUID INTAKE

Contraindications:

• debilitated patients who cannot drink adequate fluid
• side effect-flatulence

Question 2

Osmotic Laxatives (water content of stool)
Non absorbable sugars
Lactulose and Sorbitol

Answer 2

synthetic disaccharide

• bacteria degrade in colon
• increases osmotic pressure and acidification of stool
• increase stool water content

Side effects:
bloating, cramps, flatulence, sickly sweet

Question 3

Osmotic Laxatives 
(water content of stool) 
Saline and magnesium salts
Magnesium citrate
Magnesium hydroxide (MOM) 
Sodium phosphate (Fleets phospho-soda)

Answer 3

Osmotically active parties

• Mg stimulates cholecystokinin
• Increases intraluminal volume
• Stimulates intestinal activity

-High doses-rapid bowel evacuation

Saline and Magnesium 
Contraindications:
Bowel Obstruction 
Dehydration 
Electrolyte abnormalities 
-do NOT use in patients with renal failure
-very cautious in patients with CHF and liver failure 
Ischemic colitis-rare

Sodium Phosphate
Side effects:
Acute phosphate nephropathy
-intratubular deposition of calcium phosphate
Risk factors: advanced age, CHF, hepatic or renal insufficiency, volume depletion, medications: NSAIDS, ACEI, ARB, diuretics

Indications:
Magnesium citrate and sodium phosphate
–>bowel prep

Magnesium hydroxide
–>constipation

Question 4

Polyethylene Glycol
(water content of stool) 
1. Miralax, Glycolax (constipation)
2. Colyte, Golytely 
(bowel prep)

Answer 4

osmotically active
retain water in stool
softer stool, more frequent movements

bowel prep-large volumes
constipation-small daily dose

Question 5

Stimulant laxative
(Motility)
Senna
Bisacodyl

Answer 5

Senna
-converts to active metabolites in colon and stimulates myenteric plexus

Bisacodyl
-stimulates sensory nerve endings, parasympathetic stimulation, peristalsis

Side effects:
cramping and melanosis coli

Question 6

Detergent Laxatives (stool softeners)
(motility)
Docusate

Answer 6

• surfactant
• increases penetration of fluid into stool
• emulsifies feces, water, fat

Question 7

Lubricants (motility)
Glycerin suppository/enema
Mineral oil enema

Answer 7

Glycerin
osmotic-softens, lubricates stool
irritant-stimulates rectal contractions

Mineral oil

• Coats fecal material
• soften stool, lubricates

May see response in 30 min

Side effects:
mineral oil should NEVER be administered to sick, debilitated patients–>lipoid pneumonitis

Clinical indication: Fecal impaction

Question 8

Large volume enemas

Answer 8

soften stool by increasing water content
distend distal colon
induce peristalsis

clinical indications: fecal impaction