Ppt chapter 58

Drugs Affecting Gastrointestinal
Motility
Chapter 58
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins

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

Types 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 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 Stimulants
• Magnesium Sulfate (Epsom Salts)
• Magnesium Citrate (Citrate of Magnesia)
• Magnesium Hydroxide (Milk of Magnesia)
• Lactulose (Chronulac)
• Polycarbophil (FiberCon)
• Psyllium (Metamucil)

Types 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

Laxatives
• 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.)
• Pharmacokinetics
– Only minimally absorbed and exert their therapeutic
effect directly in the GI tract
• Contraindications
– Acute abdominal disorders
• Caution
– Pregnancy or lactation

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

Question
Which of the following is a very popular OTC laxative?
A. Cascara
B. Magnesium citrate
C. Bisacodyl
D. Polycarbophil

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

Types 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 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.)
– Allergy
– GI obstruction
• Caution
– Pregnancy
– Lactation

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 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 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.)
– 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

Question
Please answer the following statement as true or false.
Pepto-Bismol can be involved in salicylate toxicity.

Answer
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

Prototype Chemical Stimulant Laxative

Prototype Bulk Laxative

Prototype Lubricant Laxative

Prototype Gastrointestinal Stimulants

Prototype Antidiarrheal Drugs

Nursing Considerations for Laxatives
• Assessment: History and Physical Exam
• Nursing Diagnosis
• Implementation
• Evaluation

Nursing Considerations for
Gastrointestinal Stimulants
• Implementation
• Evaluation

Nursing Considerations for Antidiarrheal
Drugs
• Implementation
• Evaluation

Question
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

Answer
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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