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Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 37
Drugs Affecting the Lower Gastrointestinal Tract
Chapter 37
Drugs Affecting the Lower Gastrointestinal Tract
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question 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
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AnswerAnswer
• A. Proximal colon
• Rationale: Absorption of fluid and electrolytes occurs primarily in the proximal colon.
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Physiology 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.
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Large IntestinesLarge Intestines
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Pathophysiology 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.
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Antiflatulents Antiflatulents
• Antiflatulents decrease gas production.
• Prototype drug: simethicone (Mylicon)
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Simethicone: Core Drug Knowledge 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
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Simethicone: Core Drug Knowledge (cont.)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.
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Simethicone: Core Patient Variables 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.
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Simethicone: Nursing Diagnoses and Outcomes 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.
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Simethicone: Planning and InterventionsSimethicone: 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.
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Simethicone: Teaching, Assessment, and EvaluationSimethicone: 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.
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QuestionQuestion
• Simethicone has the following contraindication(s)
– A. Cardiac disease
– B. Renal insufficiency
– C. No contraindications
– D. Both A and B
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AnswerAnswer
• C. No contraindications
• Rationale: Simethicone has no contraindications or precautions.
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Antidiarrheals Antidiarrheals
• Antidiarrheals slow intestinal motility, allowing time for fluid reabsorption and better stool formation.
• Prototype drug: diphenoxylate HCl with atropine sulfate (Lomotil, Lonox)
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Diphenoxylate: Core Drug Knowledge Diphenoxylate: Core Drug Knowledge
• Pharmacotherapeutics
– Adjunct in treating diarrhea
• Pharmacokinetics
– Administered: oral. Metabolism: liver. Excreted: urine and feces.
• Pharmacodynamics
– Acts on the smooth muscle of the intestine to slow intestinal motility and prolong intestinal transit time, allowing for the reabsorption of fluid.
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Diphenoxylate: Core Drug Knowledge (cont.)Diphenoxylate: Core Drug Knowledge (cont.)
• Contraindications and precautions
– Hypersensitivity
• Adverse effects
– Drowsiness and dizziness
• Drug interactions
– MAOIs, alcohol, barbiturates, and tranquilizers
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Diphenoxylate: Core Patient Variables Diphenoxylate: Core Patient Variables
• Health status
– Assess symptoms and contraindications to therapy.
• Life span and gender
– Pregnancy Category C drug
• Lifestyle, diet, and habits
– Assess history of substance abuse.
• Environment
– Assess the environment where the drug will be given.
• Culture and inherited traits
– Assess cultural beliefs regarding bowel habits.
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Diphenoxylate: Nursing Diagnoses and Outcomes 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.
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Diphenoxylate: Planning and InterventionsDiphenoxylate: Planning and Interventions
• Maximizing therapeutic effects
– Administered as ordered
• Minimizing adverse effects
– Decrease the dosage when the number of stools decreases.
– Assess for and report signs of atropine sulfate toxicity.
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Diphenoxylate: Teaching, Assessment, and EvaluationDiphenoxylate: Teaching, Assessment, and Evaluation
• Patient and family education
– Teach patients not to exceed the prescribed dosage.
– Instruct patients to notify the prescriber if diarrhea persists for more than 2 days.
• Ongoing assessment and evaluation
– It is important to assess skin turgor and mucous membranes for loss of moisture because these signs indicate dehydration.
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QuestionQuestion
• Signs of atropine toxicity includes which of the following?
– A. Dry mouth
– B. Hypothermia
– C. Tachycardia
– D. Urinary retention
– E. All of the above
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AnswerAnswer
• 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.
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Laxatives 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)
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Magnesium Hydroxide: Core Drug Knowledge Magnesium Hydroxide: Core Drug Knowledge
• Pharmacotherapeutics
– Constipation and prepare the bowel for surgery
• Pharmacokinetics
– Local effect on GI tract. Duration: 2 to 6 hours.
• Pharmacodynamics
– Attracting and retaining water in the intestinal lumen
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Magnesium Hydroxide: Core Drug Knowledge (cont.)Magnesium Hydroxide: Core Drug Knowledge (cont.)
• Contraindications and precautions
– Abdominal pain
• Adverse effects
– Overactive bowel and fluid and electrolyte imbalance
• Drug interactions
– May decrease or increase the effects of many drugs
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Magnesium Hydroxide: Core Patient Variables Magnesium Hydroxide: Core Patient Variables • Health status
– Determine any history of renal insufficiency.
• Life span and gender
– Assess age before administration.
• Lifestyle, diet, and habits
– Determine normal fluid intake.
• Environment
– Assess the environment where the drug will be given.
• Culture and inherited traits
– Cultural variations about frequency of bowel movements
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Magnesium Hydroxide: Nursing Diagnoses and Outcomes 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.
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Magnesium Hydroxide: Planning and InterventionsMagnesium Hydroxide: Planning and Interventions
• Maximizing therapeutic effects
– The patient should follow with a full glass of water to prevent dehydration and to promote a more rapid effect.
• Minimizing adverse effects
– 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.
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Magnesium Hydroxide: Teaching, Assessment, and EvaluationMagnesium Hydroxide: Teaching, Assessment, and Evaluation
• Patient and family education
– Short-term use of medication
• Ongoing assessment and evaluation
– Assess color, consistency, and amount of stool produced to monitor effectiveness of magnesium hydroxide.
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QuestionQuestion
• Magnesium hydroxide is a laxative that can be used for long-term therapy.
– A. True
– B. False
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AnswerAnswer
• B. False
• Rationale: Magnesium hydroxide is not for long-term use. Fluid and electrolyte imbalance can occur with large doses given frequently.
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Drugs Used to Treat Irritable Bowel Syndrome 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)
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Alosetron: Core Drug Knowledge Alosetron: Core Drug Knowledge
• Pharmacotherapeutics
– Treatment of IBS
• Pharmacokinetics
– Administered: oral. Metabolism: liver. Absorption: Excreted: urine and feces.
• Pharmacodynamics
– Blocks the 5-HT3 receptor
– Alters visceral sensation, decreasing abdominal discomfort and pain
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Alosetron: Core Drug Knowledge (cont.)Alosetron: Core Drug Knowledge (cont.)
• Contraindications and precautions
– History of chronic constipation
• Adverse effects
– Constipation
• Drug interactions
– No important drug interactions with alosetron have been identified.
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Alosetron: Core Patient Variables Alosetron: Core Patient Variables
• Health status
– Assess type of IBS.
• Life span and gender
– Pregnancy Category B drug
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Alosetron: Nursing Diagnoses and Outcomes 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.
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Alosetron: Planning and InterventionsAlosetron: Planning and Interventions
• Maximizing therapeutic effects
– No specific actions are recommended.
• Minimizing adverse effects
– 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.
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Alosetron: Teaching, Assessment, and EvaluationAlosetron: Teaching, Assessment, and Evaluation
• Patient and family education
– Educate patients about the potential adverse effects.
– Instruct patients to report any constipation or signs of ischemic colitis.
• Ongoing assessment and evaluation
– Assess the patient throughout alosetron therapy for constipation.
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QuestionQuestion
• What is the major adverse effect of alosetron?
– A. Diarrhea
– B. Constipation
– C. Tachycardia
– D. Nephrotoxicity
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AnswerAnswer
• B. Constipation
• Rationale: Alosetron’s major adverse effect is constipation.
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Drugs Used to Treat Inflammatory Bowel Disease 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)
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Mesalamine: Core Drug Knowledge Mesalamine: Core Drug Knowledge
• Pharmacotherapeutics
– Ulcerative colitis and proctosigmoiditis
• Pharmacokinetics
– Formulation: tablet, capsule, suppository, and rectal suspension. Metabolism: liver. Excreted: feces.
• Pharmacodynamics
– The action of mesalamine is unknown.
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Mesalamine: Core Drug Knowledge (cont.)Mesalamine: Core Drug Knowledge (cont.)
• Contraindications and precautions
– Hypersensitivity
• Adverse effects
– Diarrhea, abdominal pain, cramps, flatulence, nausea, and headache
• Drug interactions
– Azathioprine, mercaptopurine, and salicylates
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Mesalamine: Core Patient Variables Mesalamine: Core Patient Variables
• Health status
– Assess for hypersensitivity.
• Life span and gender
– Pregnancy Category B drug
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Mesalamine: Nursing Diagnoses and Outcomes 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.
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Mesalamine: Planning and InterventionsMesalamine: Planning and Interventions
• Maximizing therapeutic effects
– Before administering the enema, shake the bottle thoroughly.
• Minimizing adverse effects
– Administer the oral medication at even intervals throughout the day.
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Mesalamine: Teaching, Assessment, and EvaluationMesalamine: Teaching, Assessment, and Evaluation
• Patient and family education
– Educate the patient about the potential adverse effects.
– Instruct the patient how to administer an enema if ordered.
• Ongoing assessment and evaluation
– Assess the patient throughout mesalamine therapy for relief of pain.
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QuestionQuestion
• Mesalamine may be prescribed for all age groups.
– A. True
– B. False
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AnswerAnswer
• B. False
• Rationale: Mesalamine is not approved for use in children.