ppt chapter 58

Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins

Drugs Affecting Gastrointestinal Motility

Drugs Affecting Gastrointestinal Motility

Chapter 58


Actions of Drugs Used to Affect Motor Activity of the GI Tract

Actions of Drugs Used to Affect Motor Activity of the GI Tract

• Speed up or improve movement of intestinal contents when movement becomes slow or sluggish (constipation)

• Increase the tone of the GI tract and stimulate motility throughout the system

• Decrease movement along the GI tract when rapid movement decreases the time for absorption of nutrients (diarrhea)


Sites of Action of Drugs Affecting GI Motility

Sites of Action of Drugs Affecting GI Motility


Types of LaxativesTypes of Laxatives

• Chemical Stimulants

– Chemically irritate the lining of the GI tract

• Bulk Stimulants

– Cause the fecal matter to increase in bulk

• Lubricants

– Help the intestinal contents move more smoothly


Types of Chemical StimulantsTypes of Chemical Stimulants

• Cascara (Generic): Reliable agent that leads to intestinal evacuation

• Senna (Senokot): Reliable drug, similar to cascara (OTC)

• Castor Oil (Neoloid): Old standby for thorough evacuation of the intestine

• Bisacodyl (Dulcolax): Very popular OTC laxative


Types of Bulk StimulantsTypes of Bulk Stimulants

• Magnesium Sulfate (Epsom Salts)

• Magnesium Citrate (Citrate of Magnesia)

• Magnesium Hydroxide (Milk of Magnesia)

• Lactulose (Chronulac)

• Polycarbophil (FiberCon)

• Psyllium (Metamucil)


Types of Lubricating LaxativesTypes of Lubricating Laxatives

• Docusate (Colace)

– Has a detergent action on the surface of the intestinal bolus, making a softer stool

• Glycerin (Sani-Supp)

– Hyperosmolar laxative used to gently evacuate the rectum without systemic effects higher in the GI tract

• Mineral Oil (Agoral Plain)

– Forms a slippery coat on the contents of the intestinal tract


LaxativesLaxatives• Actions

– Work in three ways:

• Direct chemical stimulation of the GI tract

• Production of bulk or increased fluid in the lumen

• Lubrication of the intestinal bolus to promote passage through the GI tract

• Indications

– Short-term relief of constipation

– Prevent straining when it is clinically undesirable

– Evacuate the bowel for diagnostic procedures

– Removal of ingested poisons

– Adjunct in antihelmintic therapy


Laxatives (cont.)Laxatives (cont.)

• Pharmacokinetics

– Only minimally absorbed and exert their therapeutic effect directly in the GI tract

• Contraindications

– Acute abdominal disorders

• Caution

– Pregnancy or lactation


Laxatives (cont.)Laxatives (cont.)

• Adverse Effects

– GI effects - Diarrhea, abdominal cramping, and nausea

– CNS effects – Dizziness, headache, and weakness

– CV effects – Sweating, palpitations, flushing, and fainting

– Cathartic dependency

• Drug-to-Drug Interactions

– Some interfere with the timing or process of absorption


QuestionQuestion

Which of the following is a very popular OTC laxative?

A. Cascara

B. Magnesium citrate

C. Bisacodyl

D. Polycarbophil


AnswerAnswer

C. Bisacodyl

Rationale: Bisacodyl (Dulcolax): Very popular OTC laxative.


Types of Gastrointestinal StimulantsTypes of Gastrointestinal Stimulants

• Dexpanthenol (Ilopan)

– Increases acetylcholine levels and stimulates the parasympathetic system

• Metoclopramide (Reglan)

– Blocks dopamine receptors and makes the GI cells more sensitive to acetylcholine

– Leads to increased GI activity and rapid movement of food through the upper GI tract


Gastrointestinal StimulantsGastrointestinal Stimulants

• Actions

– Stimulate parasympathetic activity within the GI tract

– Increase GI secretions and motility

• Indications

– Rapid movement of GI contents is desirable


– Rapidly absorbed

– Metabolized in the liver

– Excreted in the urine


Gastrointestinal Stimulants (cont.)Gastrointestinal Stimulants (cont.)


– Allergy

– GI obstruction

• Caution

– Pregnancy

– Lactation


Gastrointestinal Stimulants (cont.)Gastrointestinal Stimulants (cont.)

• Adverse Effects

– Nausea, vomiting, diarrhea, intestinal spasms, cramping, decreased blood pressure and heart rate, weakness, and fatigue


– Digoxin

– Cyclosporine

– Alcohol


Types of Antidiarrheal DrugsTypes of Antidiarrheal Drugs

• Bismuth Subsalicylate (Pepto-Bismol): Coats the lining of the GI tract and soothes irritation stimulating local reflexes to cause excessive GI activity and diarrhea

• Loperamide (Imodium): Has a direct effect on the muscle layers of the GI tract; slows peristalsis and allows increased time for absorption of fluid and electrolytes

• Opium Derivatives (Paregoric): Stimulates spasm within the GI tract, stops peristalsis and diarrhea


Antidiarrheal DrugsAntidiarrheal Drugs• Actions

– Slow the motility of the GI tract through direct action on the lining of the GI tract

• Indications

– Relief of symptoms of acute or chronic diarrhea

– Reduction of volume of discharge from ileostomies

– Prevention and treatment of traveler’s diarrhea


– Vary depending on agent


Antidiarrheal Drugs (cont.)Antidiarrheal Drugs (cont.)


– Allergy

• Caution

– Pregnancy

– Lactation

– History of GI obstruction

– History of acute abdominal conditions

– Diarrhea due to poisonings



• Adverse Effects

– Constipation

– Abdominal distension

– Abdominal discomfort

– Nausea

– Dry mouth

– Toxic megacolon

– Fatigue

– Weakness

– Dizziness




– Depends on the drug


QuestionQuestion

Please answer the following statement as true or false.

Pepto-Bismol can be involved in salicylate toxicity.


AnswerAnswer

True

Rationale: Bismuth Subsalicylate (Pepto-Bismol) coats the lining of the GI tract and soothes irritation stimulating

local reflexes to cause excessive GI activity and diarrhea.


Use of Laxative and Antidiarrheal Agents Across the Lifespan

Use of Laxative and Antidiarrheal Agents Across the Lifespan


Prototype Chemical Stimulant LaxativePrototype Chemical Stimulant Laxative


Prototype Bulk Laxative Prototype Bulk Laxative


Prototype Lubricant LaxativePrototype Lubricant Laxative


Prototype Gastrointestinal StimulantsPrototype Gastrointestinal Stimulants


Prototype Antidiarrheal Drugs Prototype Antidiarrheal Drugs


Nursing Considerations for Laxatives Nursing Considerations for Laxatives

• Assessment: History and Physical Exam

• Nursing Diagnosis

• Implementation

• Evaluation


Nursing Considerations for Gastrointestinal StimulantsNursing Considerations for Gastrointestinal Stimulants



• Implementation

• Evaluation


Nursing Considerations for Antidiarrheal Drugs

Nursing Considerations for Antidiarrheal Drugs



• Implementation

• Evaluation


QuestionQuestion

Why should laxatives be taken only on a short-term basis?

A. To prevent a fluid volume deficit

B. To prevent cathartic dependence

C. To obtain relief of abdominal distention

D. To obtain relief of intestinal cramping


AnswerAnswer

B. To prevent cathartic dependence

Rationale: Administer laxative only as a temporary measure to prevent development of cathartic dependence.

ppt chapter 58

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