1. Chapter 79
Laxatives 1

2. Laxatives Used to ease or stimulate defecation Soften the stool
Increase stool volume
Hasten fecal passage through the intestine
Facilitate evacuation from the rectum
Misuse comes from misconceptions of what constitutes normal bowel function 2

3. Laxative Effect vs. Catharsis
Production of soft, formed stool over 1 or more days
Relatively mild
Catharsis
Prompt, fluid evacuation of the bowel
Fast and intense 3

4. Function of the Colon Absorbs water and electrolytes
Absorption of nutrients is minimal
1500 mL of fluid enters colon each day
90% of fluid is absorbed
Delayed transport through colon causes excessive fluid absorption and hard stool
Frequency of bowel elimination varies widely (from 2 to 3 times/day to 2 times/week) 4

5. Dietary Fiber
Proper bowel function is highly dependent on dietary fiber (bran is best source)
Benefits of fiber
Absorbs water: Softens feces and increases size
Can be digested by colonic bacteria, whose growth increases fecal mass
Low-fiber diet: Frequent cause of constipation 5

6. Constipation One of the most common GI disorders
People seek medical help for constipation in the United States at least 2.5 million times a year
Hundreds of millions of dollars a year are spent on laxatives
Constipation may be defined as:
Hard stools, infrequent stools, excessive straining, prolonged effort, sense of incomplete evacuation, unsuccessful defecation 6

7. Indications for Laxative Use
Obtain fresh stool sample
Empty bowel before treatment or procedure
Expel dead parasites after treatment
Modify effluent from ileostomy or colostomy
Constipation (multiple causes, including pregnancy and opioid use)
Prevent fecal impaction in bedridden patients
Remove poisons 7

8. Contraindications to Laxative Use
Abdominal pain, nausea, cramps, or other symptoms of appendicitis, regional enteritis, diverticulitis, or ulcerative colitis
Acute surgical abdomen
Fecal impaction or bowel obstruction
Habitual use
Use with caution in pregnancy and lactation 8

9. Classification of Laxatives
Bulk-forming laxatives
Psyllium [Metamucil]
Surfactant laxatives
Docusate sodium [Colace]
Stimulant laxatives
Bisacodyl [Dulcolax]
Osmotic laxatives
Milk of magnesia (MOM) 9

10. Classification of Laxatives: Therapeutic Effect
Group I: Act rapidly (within 2 to 6 hours) and give stool a watery consistency; useful for preparing bowel for diagnostic procedures or surgery
Group II: Intermediate latency (6 to 12 hours); produce a semifluid stool
Group III: Most frequently abused by the general public; act slowly (1 to 3 days) to produce a soft, formed stool; uses include treating chronic constipation and preventing straining at stool 10

11. Bulk-Forming Laxatives
Function similarly to dietary fiber: Swell with water to form a gel that softens and increases fecal mass
Preferred temporary treatment of constipation
Used for diverticulosis and irritable bowel syndrome
Adverse effects are minimal
Esophageal obstruction 11

12. Surfactant Laxatives
Produce a soft stool several days after onset of treatment
Alter stool consistency by lowering surface tension, which facilitates penetration of water into feces
May also act on intestinal wall to (1) inhibit fluid absorption and (2) stimulate secretion of water and electrolytes into intestinal lumen; in this respect, surfactants resemble stimulant laxatives 12

13. Stimulant Laxatives Two effects on bowel: Widely used and abused
Stimulate intestinal motility
Increase amounts of water and electrolytes in intestinal lumen
Widely used and abused
Legitimately used for opioid-induced constipation and for constipation from slow intestinal transit 13

14. Osmotic Laxatives
Laxative salts (sodium phosphate, magnesium hydroxide)
Poorly absorbed salts that draw water into intestinal lumen; fecal mass softens and swells, wall stretches, and peristalsis is stimulated
Low doses: Results in 6 to 12 hours
High doses: Results in 2 to 6 hours 14

15. Osmotic Laxatives Adverse effects Dehydration: Substantial water loss
Acute renal failure
Sodium retention: Exacerbated heart failure, hypertension, edema 15

16. Other Laxatives Lubiprostone Selective chloride channel activator
By activating (opening) chloride channels in epithelial cells lining the intestine, lubiprostone (1) promotes secretion of chloride-rich fluid into the intestine and (2) enhances motility in the small intestine and colon
The result is spontaneous evacuation of a semisoft stool, usually within 24 hours

17. Other Laxatives
Mineral oil: Mixture of indigestible and poorly absorbed hydrocarbons. Laxative action is produced by lubrication. Mineral oil is especially useful when administered by enema to treat fecal impaction.
Adverse effects: Lipid pneumonia, anal leakage, and deposition of mineral oil in the liver.

18. Other Laxatives
Glycerin suppository: Osmotic agent that softens and lubricates hardened, impacted feces
May also stimulate rectal contraction
Evacuation occurs about 30 minutes after suppository insertion
Useful for reestablishing normal bowel function after termination of chronic laxative use

19. Bowel-Cleansing Products for Colonoscopy
Allow for good visualization of the bowel
Types
Sodium phosphate
Hypertonic with body fluids
Can cause dehydration and electrolyte disturbance
Possibility of renal damage
Polyethylene glycol (PEG) plus electrolytes (ELS)
Isotonic with body fluids
Requires ingestion of large volume of bad-tasting liquid
Combination of sodium picosulfate, magnesium oxide, and citric acid

20. Polyethylene Glycol – Electrolyte Solutions
CoLyte, GoLytely
Volume administered is huge, typically 4 L. Patients must ingest 250 to 300 mL every 10 minutes for 2 to 3 hours. With HalfLytely and MoviPrep, the volume is cut in half.
Most common adverse effects are nausea, bloating, and abdominal discomfort.

21. Sodium Phosphate Products
Osmotic laxatives that draw water into intestinal lumen, which softens and swells fecal mass, which stretches intestinal wall to stimulate peristalsis
Adverse effects: Nausea, bloating, abdominal discomfort; risk of dehydration, electrolyte disturbances, and kidney damage
Hyperphosphatemia, which can cause acute, reversible renal damage and possibly chronic, irreversible renal damage

22. Combination Product
Magnesium oxide/anhydrous citric acid/sodium picosulfate [Prepopik] has been approved for preparation for colonoscopy in adults.
Adverse effects: Possible electrolyte and fluid imbalances, renal impairment, seizures, and arrhythmia secondary to electrolyte abnormalities. Caution must be used in patients with reduced renal function. The most common adverse reactions are nausea, headache, and vomiting.

23. Laxative Abuse Causes Consequences
Misconception that bowel movements must occur daily
Can perpetuate their own use
Bowel replenishment after evacuation can take 2 to 5 days; often mistaken for constipation
Consequences
Diminished defecatory reflexes, leading to further reliance on laxatives
Electrolyte imbalance, dehydration, colitis 23

24. Question 1
The nurse identifies which of the following as the most common type of laxative abused by the general public?
A. Magnesium hydroxide [Milk of Magnesia]
B. Docusate sodium [Colace]
C. Bisacodyl [Dulcolax]
D. Polyethylene glycol [MiraLax]
Answer: C
Rationale: Stimulant laxatives (bisacodyl, senna, castor oil) are most commonly abused by the general public. The nurse should discourage use of these drugs for occasional relief of constipation.

25. Question 2
A patient who has been taking a long-acting morphine to treat severe pain for a few months complains of constipation. The nurse anticipates which of the following will be prescribed for the patient?
A. Polycarbophil [FiberCon]
B. Mineral oil
C. Psyllium [Metamucil]
D. Senna [Senokot]
Answer: D
Rationale: Stimulant laxatives are commonly used to treat opioid-induced constipation.

26. Question 3
A patient is prescribed bisacodyl. Which of the following should the nurse include in patient teaching?
A. Your urine will turn yellow-brown when taking this medication.
B. Crush the bisacodyl tablet and sprinkle it on your food.
C. Chew the bisacodyl tablet.
D. Do not take the bisacodyl with an antacid.
Answer: D
Rationale: Instruct patients to take oral bisacodyl no sooner than 1 hour after ingesting milk or antacids. Instruct patients to swallow the tablets intact, without crushing or chewing. Inform patients that bisacodyl suppositories may cause a burning sensation, and warn them that prolonged use can cause proctitis. Senna can cause the patient’s urine to turn a harmless yellow-brown or pink.

27. Question 4
The nurse identifies which of the following laxatives as having the added response of ridding the body of ammonia?
A. Polyethylene glycol
B. Lactulose
C. Lubiprostone
D. Mineral oil
Answer: B
Rationale: In addition to its laxative action, lactulose can enhance intestinal excretion of ammonia. This property has been exploited to lower blood ammonia content in patients with portal hypertension and hepatic encephalopathy secondary to chronic liver disease.