Chapter 37 - Constipation and Elimination Problems

Question 1

Bulk-forming laxatives (class = laxatives)

Answer 1

Add mass to feces, stimulating peristalsis and defecation. Must be taken with water to avoid obstruction.
• Most desirable laxative for long-term use
• Drug: Psyllium preparations –> Metamucil

Question 2

Surfactant laxatives (class = laxatives)

Answer 2

Decrease the surface tension of the fecal mass to allow water and fat to penetrate into the stool, making it softer and easier to expel.
•Have little true laxative effect
•Drug: docusate sodium –> Colace (oil lubricates and softens stool; 1-3 days for max effect

Question 3

Lubricant Laxatives (class = laxatives)

Answer 3

Lubricate the fecal mass and slow colonic absorption of water from the fecal mass. May interfere with the absorption of fat-soluble vitamins and if aspirated may result in a lipid aspiration pneumonia
•Drug: Mineral oil –> used to soften hard stools, takes about 6-8 hours to take effect

Question 4

Stimulant cathartics (class = cathartics)

Answer 4

Irritate the GI mucosa, pull water into the colon, and stimulate peristalsis. Produce a watery stool and may lead to fluid, electrolyte, and acid-base imbalances
• Strongest and most abused laxative products
•Drug: bisacodyl –> Dulcolax

Question 5

Saline laxatives (class = cathartics)

Answer 5

Increase the osmotic pressure in the intestinal lumen, resulting in the retention of water, which distends the bowel and stimulates peristalsis. They produce a semifluid stool and may lead to fluid and electrolyte imbalances
•OTC, highly used med, easy to take, good for kids
•Drug: polyethelene glycol  Miralax

Question 6

Miscellaneous Agents for Constipation

• Lactulose

Answer 6

 Lactulose
 MOA: Exerts an osmotic effect, pulling water into the colon and stimulating peristalsis.
 Use: Constipation, also useful in treating hepatic encephalopathy by decreasing the production of the waste product ammonia

Question 7

Miscellaneous Agents for Constipation

• Lubriprostone

Answer 7

 Lubriprostone
 MOA: Increasing intestinal fluid secretion, stimulating intestinal motility and defecation
 Use: Chronic idiopathic constipation