Ppt chapter 37

Chapter 37
Drugs Affecting the Lower
Gastrointestinal Tract
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

Question
• In what part of the colon are the majority of fluids and
electrolytes reabsorbed?
– A. Proximal colon
– B. Mid-segment of the colon
– C. Distal colon
– D. Rectum

Answer
• A. Proximal colon
• Rationale: Absorption of fluid and electrolytes occurs
primarily in the proximal colon.

Physiology
• The large intestine is approximately 5 feet long (1.5 m)
and 2.5 inches (6.5 cm) in diameter.
• The longitudinal muscle fibers on the outer surface of the
large intestine are in three layers.
• The large intestine is composed of the cecum, colon,
rectum, and anal canal.
• The contents from the small intestine enter the cecum
through the ileocecal valve.
• Peristalsis moves the contents through the small and
large intestines.
• Large amounts of mucus are secreted by goblet cells in
the epithelial layer of the large intestine.

Large Intestines

Pathophysiology
• Flatus is a normal by-product of digestion.
• Diarrhea is the frequent passage of loose or liquid
stools.
• Constipation is infrequent or incomplete passage of
hard stools resulting from a decrease in peristaltic
activity.
• Irritable bowel syndrome (IBS) is a common disorder
of the intestines characterized by altered bowel habits
and pain.
• Inflammatory bowel disease (IBD) is a general term
that includes both ulcerative colitis and Crohn disease.

Antiflatulents
• Antiflatulents decrease gas production.
• Prototype drug: simethicone (Mylicon)

Simethicone: Core Drug Knowledge
• Pharmacotherapeutics
– Relieves the discomfort of excess gas
• Pharmacokinetics
– Not absorbed from GI tract. Excreted: feces.
• Pharmacodynamics
– Defoaming action that alters the surface tension of
gas bubbles

Simethicone: Core Drug Knowledge
(cont.)
• Contraindications and precautions
– Simethicone has no contraindications or precautions.
• Adverse effects
– No substantial adverse reactions
• Drug interactions
– No drug interactions with simethicone are known.

Simethicone: Core Patient Variables
• Health status
– Assess bowel sounds and abdominal pai.
• Lifestyle, diet, and habits
– Assess dietary choices.
• Environment
– Assess the environment where the drug will be given.

Simethicone: Nursing Diagnoses and
Outcomes
• Acute Pain related to the presence of flatus
– Desired outcome: Within 2 to 3 hours of using
simethicone, the patient will experience a decrease in
abdominal pain and distention.

Simethicone: Planning and Interventions
• Maximizing therapeutic effects
– Simethicone should be given after meals and at
bedtime to increase its effectiveness.
– The suspension form of the drug must be shaken to
ensure that the active ingredients are well dispersed.

Simethicone: Teaching, Assessment, and
Evaluation
• Patient and family education
– Teach patients to take simethicone after each meal
and at bedtime.
– Caution patients not to increase the dosage.
• Ongoing assessment and evaluation
– Assess abdominal pain and distention periodically
throughout simethicone therapy to monitor the
effectiveness of the drug.

Question
• Simethicone has the following contraindication(s)
– A. Cardiac disease
– B. Renal insufficiency
– C. No contraindications
– D. Both A and B

Answer
• C. No contraindications
• Rationale: Simethicone has no contraindications or
precautions.

Antidiarrheals
• Antidiarrheals slow intestinal motility, allowing time for
fluid reabsorption and better stool formation.
• Prototype drug: diphenoxylate HCl with atropine sulfate
(Lomotil, Lonox)

Diphenoxylate: Core Drug Knowledge
– Adjunct in treating diarrhea
– Administered: oral. Metabolism: liver. Excreted:
urine and feces.
– Acts on the smooth muscle of the intestine to slow
intestinal motility and prolong intestinal transit time,
allowing for the reabsorption of fluid.

Diphenoxylate: Core Drug Knowledge
(cont.)
– Hypersensitivity
• Adverse effects
– Drowsiness and dizziness
– MAOIs, alcohol, barbiturates, and tranquilizers

Diphenoxylate: Core Patient Variables
• Health status
– Assess symptoms and contraindications to therapy.
• Life span and gender
– Pregnancy Category C drug
– Assess history of substance abuse.
• Environment
• Culture and inherited traits
– Assess cultural beliefs regarding bowel habits.

Diphenoxylate: Nursing Diagnoses and
Outcomes
• Diarrhea related to the causative factor (if identified)
– Desired outcome: Diarrhea will be controlled
through the use of diphenoxylate HCl with atropine
sulfate.
• Risk for Injury related to drowsiness and dizziness
secondary to drug therapy
– Desired outcome: The patient will not sustain
injury from drug therapy.

Diphenoxylate: Planning and
Interventions
– Administered as ordered
• Minimizing adverse effects
– Decrease the dosage when the number of stools
decreases.
– Assess for and report signs of atropine sulfate
toxicity.

Diphenoxylate: Teaching, Assessment,
and Evaluation
– Teach patients not to exceed the prescribed dosage.
– Instruct patients to notify the prescriber if diarrhea
persists for more than 2 days.
– It is important to assess skin turgor and mucous
membranes for loss of moisture because these signs
indicate dehydration.

Question
• Signs of atropine toxicity includes which of the following?
– A. Dry mouth
– B. Hypothermia
– C. Tachycardia
– D. Urinary retention
– E. All of the above

Answer
• E. All of the above
• Rationale: Assess for and report signs of atropine
sulfate toxicity (e.g., dry mouth, flushing,
hypothermia, tachycardia, and urinary retention)
because this condition requires immediate medical
attention.

Laxatives
• Drugs used to treat constipation are referred to as
laxatives.
• Laxatives are drugs that act directly on the intestine to
promote peristalsis and evacuation of the bowel.
• Laxatives are classified as saline, hyperosmotic,
stimulant, and bulk forming.
• Saline laxatives
– Attract or retain water in the intestinal lumen,
resulting in an increased intraluminal pressure that
stimulates peristalsis.
• Prototype drug: magnesium hydroxide (Milk of Magnesia)

Magnesium Hydroxide: Core Drug
Knowledge
– Constipation and prepare the bowel for surgery
– Local effect on GI tract. Duration: 2 to 6 hours.
– Attracting and retaining water in the intestinal lumen

Magnesium Hydroxide: Core Drug
Knowledge (cont.)
– Abdominal pain
• Adverse effects
– Overactive bowel and fluid and electrolyte imbalance
– May decrease or increase the effects of many drugs

Magnesium Hydroxide: Core Patient
Variables
• Health status
– Determine any history of renal insufficiency.
– Assess age before administration.
– Determine normal fluid intake.
• Environment
• Culture and inherited traits
– Cultural variations about frequency of bowel
movements

Magnesium Hydroxide: Nursing Diagnoses
and Outcomes
• Constipation related to dietary factors, fluid restrictions,
decreased peristalsis, lack of activity, changes in activity,
postoperative state, GI disease or malfunction, or
adverse effects from other drug therapy.
– Desired outcome: The patient will have a bowel
movement after taking magnesium hydroxide.

Magnesium Hydroxide: Planning and
Interventions
– The patient should follow with a full glass of water to
prevent dehydration and to promote a more rapid
effect.
– Limit to short-term use.
– At least 2 hours should pass between administration
of magnesium hydroxide and drugs that are known
to interact with it.

Magnesium Hydroxide: Teaching,
Assessment, and Evaluation
– Short-term use of medication
– Assess color, consistency, and amount of stool
produced to monitor effectiveness of magnesium
hydroxide.

Question
• Magnesium hydroxide is a laxative that can be used for
long-term therapy.
– A. True
– B. False

Answer
• B. False
• Rationale: Magnesium hydroxide is not for long-term use.
Fluid and electrolyte imbalance can occur with large
doses given frequently.

Drugs Used to Treat Irritable Bowel
Syndrome
• Serotonin receptors in the bowel play a role in bowel
motility.
• Drugs that work at these receptors can alter symptoms
of IBS.
• Blockade of serotonin receptor subtype 3 (5-HT3)
decreases the diarrhea associated with IBS.
• Prototype drug: alosetron (Lotronex)

Alosetron: Core Drug Knowledge
– Treatment of IBS
– Administered: oral. Metabolism: liver. Absorption:
Excreted: urine and feces.
– Blocks the 5-HT3 receptor
– Alters visceral sensation, decreasing abdominal
discomfort and pain

Alosetron: Core Drug Knowledge (cont.)
– History of chronic constipation
• Adverse effects
– Constipation
– No important drug interactions with alosetron have
been identified.

Alosetron: Core Patient Variables
• Health status
– Assess type of IBS.
– Pregnancy Category B drug

Alosetron: Nursing Diagnoses and
Outcomes
• Risk for Altered Elimination, Constipation, related to
potential adverse effects of alosetron
– Desired outcome: The patient will not develop
serious constipation while on alosetron.

Alosetron: Planning and Interventions
– No specific actions are recommended.
– Confirm that the patient has received the Medication
Guide from the prescriber before starting therapy
and has read it and understands it.
– Answer questions about therapy.

Alosetron: Teaching, Assessment, and
Evaluation
– Educate patients about the potential adverse effects.
– Instruct patients to report any constipation or signs
of ischemic colitis.
– Assess the patient throughout alosetron therapy for
constipation.

Question
• What is the major adverse effect of alosetron?
– A. Diarrhea
– B. Constipation
– C. Tachycardia
– D. Nephrotoxicity

Answer
• B. Constipation
• Rationale: Alosetron’s major adverse effect is
constipation.

Drugs Used to Treat Inflammatory Bowel
Disease
• Drug therapy cannot cure IBD.
• The drug groups used to treat IBD include the 5-
aminosalicylic acid (5-ASA) preparations, corticosteroids,
and drugs that suppress the immune system.
• 5-ASA preparations
– Aminosalicylates (5-ASA) are the anti-inflammatory
drugs most commonly prescribed for IBD.
• Prototype drug: mesalamine (Asacol, Pentasa, Lialda)

Mesalamine: Core Drug Knowledge
– Ulcerative colitis and proctosigmoiditis
– Formulation: tablet, capsule, suppository, and rectal
suspension. Metabolism: liver. Excreted: feces.
– The action of mesalamine is unknown.

Mesalamine: Core Drug Knowledge (cont.)
– Hypersensitivity
• Adverse effects
– Diarrhea, abdominal pain, cramps, flatulence,
nausea, and headache
– Azathioprine, mercaptopurine, and salicylates

Mesalamine: Core Patient Variables
• Health status
– Assess for hypersensitivity.
– Pregnancy Category B drug

Mesalamine: Nursing Diagnoses and
Outcomes
• Risk for Altered Elimination, Constipation, related to
potential adverse effects of mesalamine
– Desired outcome: The patient will not develop
serious constipation while on mesalamine.
• Acute pain related to drug-induced adverse GI effects
– Desired outcome: The patient will take
acetaminophen for pain as needed.

Mesalamine: Planning and Interventions
– Before administering the enema, shake the bottle
thoroughly.
– Administer the oral medication at even intervals
throughout the day.

Mesalamine: Teaching, Assessment, and
Evaluation
– Educate the patient about the potential adverse
effects.
– Instruct the patient how to administer an enema if
ordered.
– Assess the patient throughout mesalamine therapy
for relief of pain.

Question
• Mesalamine may be prescribed for all age groups.
– A. True
– B. False

Answer
• B. False
• Rationale: Mesalamine is not approved for use in
children.

Ppt chapter 37

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