Ppt chapter 37

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

Chapter 37

Drugs Affecting the Lower Gastrointestinal Tract

Chapter 37

Drugs Affecting the Lower Gastrointestinal Tract


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


AnswerAnswer

• A. Proximal colon

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


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.


Large IntestinesLarge Intestines


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.


Antiflatulents Antiflatulents

• Antiflatulents decrease gas production.

• Prototype drug: simethicone (Mylicon)


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


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.


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.


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.


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.


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.


QuestionQuestion

• Simethicone has the following contraindication(s)

– A. Cardiac disease

– B. Renal insufficiency

– C. No contraindications

– D. Both A and B


AnswerAnswer

• C. No contraindications

• Rationale: Simethicone has no contraindications or precautions.


Antidiarrheals 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 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.)Diphenoxylate: Core Drug Knowledge (cont.)


– Hypersensitivity

• Adverse effects

– Drowsiness and dizziness


– MAOIs, alcohol, barbiturates, and tranquilizers


Diphenoxylate: Core Patient Variables 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 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 InterventionsDiphenoxylate: 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 EvaluationDiphenoxylate: 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.


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


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.


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)


Magnesium Hydroxide: Core Drug Knowledge 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.)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 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 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 InterventionsMagnesium 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 EvaluationMagnesium Hydroxide: Teaching, Assessment, and Evaluation


– Short-term use of medication


– Assess color, consistency, and amount of stool produced to monitor effectiveness of magnesium hydroxide.


QuestionQuestion

• Magnesium hydroxide is a laxative that can be used for long-term therapy.

– A. True

– B. False


AnswerAnswer

• 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 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 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.)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 Alosetron: Core Patient Variables

• Health status

– Assess type of IBS.


– Pregnancy Category B drug


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.


Alosetron: Planning and InterventionsAlosetron: 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 EvaluationAlosetron: 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.


QuestionQuestion

• What is the major adverse effect of alosetron?

– A. Diarrhea

– B. Constipation

– C. Tachycardia

– D. Nephrotoxicity


AnswerAnswer

• B. Constipation

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


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)


Mesalamine: Core Drug Knowledge 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.)Mesalamine: Core Drug Knowledge (cont.)


– Hypersensitivity

• Adverse effects

– Diarrhea, abdominal pain, cramps, flatulence, nausea, and headache


– Azathioprine, mercaptopurine, and salicylates


Mesalamine: Core Patient Variables Mesalamine: Core Patient Variables

• Health status

– Assess for hypersensitivity.


– Pregnancy Category B drug


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.


Mesalamine: Planning and InterventionsMesalamine: 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 EvaluationMesalamine: 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.


QuestionQuestion

• Mesalamine may be prescribed for all age groups.

– A. True

– B. False


AnswerAnswer

• B. False

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

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