DRUGS AFFECTING THE
DIGESTIVE SYSTEM
Chapters 56, 59, 62
By Sandy Kaminski
Chapter 56:
Physiology of the Digestive System
The organs of the
digestive system
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Oral cavity
Esophagus
Stomach
Small intestine
Large intestine
Pancreas
Gallbladder
Liver
The Main Function of the GI System
- To provide the body with fluids, nutrients, and electrolytes in forms that can be used at
the cellular level.
- The system also disposes of waste products that result from the digestive process.
• Saliva
• Gastric Juices
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mucus
digestive enzymes
hydrochloric acid
Electrolytes
• Pancreatic juices
• amylase
• lipase
• trypsin and chymotrypsin
• Bile
Effects of Drugs on the Digestive
System
• To relieve symptoms and disorders of the
digestive system
• To alter the digestive system secretion,
absorption, or motility
• Drugs used may also cause digestive symptoms
• ie, nausea, vomiting, constipation, diarrhea, abdominal pain
Questions:
The major digestive enzyme
in gastric juice is
pancreatase.
• F. The major digestive
enzyme in gastric juice is
pepsin, a proteolytic
enzyme.
The parasympathetic
nervous system increases
motility and secretions.
•T
Blood flow increases during
digestion, absorption, and
parasympathetic
stimulation
•T
Questions
• The sympathetic nervous
•F
system (fight or flight)
increase gastric motility
and secretions.
• The GI secretions can
break down medications
so they can be absorbed
or they may destroy the
medications.
•T
Chapter 59:
Drugs Used for Peptic Ulcer (PUD) and
Acid Reflux Disorders (GERD)
H.Pylori Agents (Antibiotics)
Antacids
Proton-pump Inhibitors
Peptic Ulcer Disease (PUD)
• Attributed to an imbalance
between cell-destructive
and cell-protective effects
• Such as
• gastric acid
• Pepsin
• H. pylori infection
• NSAIDs
• Stress
• Cigarette smoking
PUD
• Gastric Acid
• secreted by parietal cells in the mucosa of the stomach antrum, near
the pylorus
• Dissolve food
• Act as a bactericide
• Convert pepsinogen to pepsin
• Pepsin
• A proteolytic enzyme that helps digest protein but can also digest the
stomach wall
• Proton-pump system
catalyzes the production of gastric acid and acts as a gastric acid
(proton) pump to move gastric acid from parietal cells in the mucosal
lining of the stomach into the stomach lumen.
PUD
• Helicobacter pylori (H. pylori)
• Bacterium found in GI tract of 75% in those with gastric ulcers and
more than 90% in those with duodenal ulcers
• It colonizes the mucus-secreting epithelial cells of the stomach
mucosa and is thought to produce gastritis and ulceration by impairing
mucosal function.
 Antibiotics are used to eradicate H. pylori
 amoxicillin, clarithromycin, metronidazole, tetracycline
• Cell-protective effects
• secretion of mucus and bicarbonate
• dilution of gastric acid by food and secretions
• prevention of diffusion of hydrochloric acid from the stomach lumen back
into the gastric mucosal lining
• the presence of prostaglandin E
• alkalinization of gastric secretions by pancreatic juices and bile
Gastroesophageal Reflux Disease
(GERD)
• Most common disorder
of the esophagus
• Regurgitation of gastric
contents (gastric acid
and pepsin) into
esophagus
• Main cause is
incompetent lower
esophageal sphincter
(LES)
• Main symptoms –
heartburn and pain on
swallowing
Risk factors that contribute to impaired
contraction of the LES include
• foods (eg, fats, chocolate)
• fluids (eg, alcohol, caffeinated beverages)
• medications (eg, estrogens, progesterone, beta-agonists, anti-
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cholinergics, calcium channel blockers, narcotics, nitrates)
gastric distension
cigarette smoking
recumbent posture
Obesity
Pregnancy
What can PUD and GERD lead to?
• PUD
• Bleeding
• Perforation
• Obstructions
• GERD
• Barrett’s esophagus
• Tissue lining changes and resembles that of instestine
• 30 to 125 times more likely to develop esophageal cancer
• Esophageal cancer
• Laryngeal cancer
• Erosive esophagitis
• Esophageal strictures
Antacids
 Alkaline substances that
neutralize acids
 Raising the pH to
approximately 3.5
neutralizes more than 90%
of gastric acid and iinhibits
conversion of pepsinogen to
pepsin
 Commonly used antacids
are aluminum, magnesium,
and calcium compounds
 Used to treat PUD, GERD,
esophagitis, heartburn,
gastritis, GI bleeding, stress
ulcers
Antacids: Drug Interactions
• Most often they decrease the absorption of other
medications by the process of chelation
• Chelation
• Chemical binding, or inactivation, of another drug
• Produces insoluble complexes
• Result: reduced drug absorption
• also affect the absorption of some nutrients.
• Dietary folate, Fe, Ca, and Vit B12 are better absorbed in acidic
environment and therefore deficiencies may occur.
Antacids: Nursing Implications
• Assess for allergies
• Preexisting conditions that may restrict the use of
antacids include
• Electrolyte imbalances
• Renal disease
• DM
• Pregnancy
• GI obstruction
• HF
Histamine2 Receptor Antagonists
(H2RAs)
 Histamine causes strong stimulation of gastric acid secretion
 H2RAs inhibit both basal secretion of gastric acid and
secretion stimulated by histamine, acetylcholine, and gastrin
 Decrease amount, acidity, and pepsin content of gastric juices
 Cimetidine, ranitidine (Zantac), famotidine are available H2RAs
H2 Antagonists: Nursing Implications
• Assess for allergies and impaired renal or liver function
• Dose must be reduced in renal impairment
• Use with caution in clients who are confused, disoriented,
or elderly
• Take 1 hour before or after antacids
• Available in both OTC and Rx preparations
• For intravenous doses
• follow administration guidelines
Proton Pump Inhibitors (PPIs)
• Strong inhibitors of gastric acid secretion
• Bind irreversibly to the gastrin proton pump to prevent
release of gastric acid from parietal cells thereby blocking
final step of acid production
• Suppress gastric acid secretion from parietal cells in
response to all primary stimuli (histamine, gastrin, and
acetylcholine)
• Available preparations:
• Omeprazole, esomeprazole, lansoprazole, pantoprazole, and
rabeprazole
Proton Pump Inhibitors: Nursing
Implications
• Assess for allergies and history of liver disease
• Pantoprazole is available for parenteral administration,
and can be used for clients who are unable to take oral
medications
• Safe for short-term therapy
• Use cautiously in those with severe liver impairment
• Lansoprazole and rabeprazole
Helicobacter Pylori Agents
• Recommended treatment includes
• Two or three antimicrobials
• Amoxicillin, clarithromycin, metronidazole, tetracycline
• Single agent not used b/c of concern about emergence of drug-resistant
H. pylori
• PPI or H2RA
• PPI = proton-pump inhibitor
• H2RA = Histamine 2 Receptor Antagonists
• Accelerates symptom relief and healing of the ulcer
Questions:
• Risk factors for PUD include stress,
NSAID ingestion, Helicobacter
pylori infection, and cigarette
smoking.
• Prostaglandin E and mucus are cell-
protecting effects that protect the
wall from injury.
• GERD is thought to be the result of
an incompetent upper esophageal
sphincter.
•T
•T
•F
- lower esophageal sphincter
Chapter 62:
Anti-Emetics
Definitions
• Nausea: unpleasant sensation of abd discomfort
accompanied by a desire to vomit. May occur without
vomiting.
• Vomiting: expulsion of stomach contents through the
mouth, May occur without prior nausea.
• Occurs when the vomiting centre (VC) or chemoreceptor trigger
zone (CTZ) are stimulated
Causes of N/V in hospital
• Gastrointestinal disorders
• including infection or inflammation in the GI tract, liver, gall-bladder,
or pancreas
• impaired GI motility and muscle tone (eg, gastroparesis)
• overeating or ingestion of foods or fluids that irritate the GI mucosa
• Cardiovascular, infectious, neurologic, or metabolic
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disorders
Drug therapy
Pain and other noxious stimuli
Emotional disturbances; physical or mental stress
Radiation therapy
Motion sickness
Post-operative status
Mechanism of Action of Anti-Emetics
• blocking one of the vomiting pathways, thus blocking the
stimulus that induces vomiting
• several different therapeutic classifications
• anti-cholinergic
• anti-dopaminergic
• anti-histaminic
• anti- serotonergic effects
• more effective in prophylaxis than treatment
• Eg. Administering Morphine IV with Gravol IV
• Eg. Taking anti-motion meds 30 minutes prior to getting on the
boat!!
CTZ – Chemoreceptor Trigger Zone
Classifications of Anti-emetics – all lumped into anti-cholinergics /
anti-dopminergics/ anti-histaminic/anti-serononergic
1. Phenothiazines
• Block dopamine from receptor sites in brain and CTZ
• (chemoreceptor trigger zone)
• chlorpromazine (Largactil) is the prototype
• prochlorperazine (Stemetil)
• CNS depressant – therefore causes sedation
• Effective for n/v induced by drugs and radiation therapy
• Not effective for motion sickness
2. Anti-histamines
• block action of acetylcholine in brain (anti-cholinergic effects)
• Dimenhydrinate (Gravol) and meclizine (Bonamine)
• effective in treating motion sickness
Classifications of Anti-emetics – all lumped into anti-cholinergics /
anti-dopminergics / anti-histaminic / anti-serononergic
3. Corticosteriods
• Block prostaglandin activity in the cerebral cortex
• Dexamethasone (Decadron)
• Commonly used in the management of chemotherapy-induced
emesis and intra-operatively
• Causes euphoria, insomnia
4. Benzodiazapines
• Produce relaxation and inhibit cerebral cortex input to vomiting
center
• lorazepam (Ativan)
• Anticipatory chemotherapy induced n/v
Classifications of Anti-emetics – all lumped into anti-cholinergics /
anti-dopminergics/ anti-histaminic/anti-serononergic
5. Prokinetic Agents
• Increase the release of Ach from the GI tract
• metoclopramide (Maxeran)
• Increases GI motility
• Used in gastroparesis (gastric retention of foods)
• May increase the effects of alcohol
6. 5-Hydroxytryptamine 3 (5-HT3 or Serotonin Receptor
Antagonists)
• Antagonize serotonin receptors
• ondansetron (Zofran)
• Moderate to severe n/v (cancer therapy, post-op)
• May cause diarrhea, headache, muscle aches, elevated liver
enzymes
What’s important for me to know about anti-emetics?
• Drug selection, dose and route depend on the cause of
the nausea/vomiting
• Most adverse affects are sedation, drowsiness, dry
mouth, diarrhea or constipation, and headache
• Multi-drug regimens may be used to treat n/v
• Use in special populations should be considered
• Eg. Older adults – increased sedative effects
• Eg. Scopolamine not recommended in pediatric population
• Eg. Metoclopramide doses should be reduced in renal failure
patients
What’s important for me to know about anti-emetics?
• Antiemetics have anticholinergic, antidopaminergic,
antihistaminic, or antiserotonergic effects. Most exert an
effect on the vomiting center, CTZ, cerebral cortex,
vestibular apparatus, or a combination of these areas
• Pretreatment is usually most effective
• 5-HT3 receptor antagonists like ondansetron are usually
considered the most effective antiemetics.
Question – T or F
• The benzodiazapine antianxiety drugs are used as anti-
emetics in multidrug regimens to prevent nausea and
vomiting associated with chemotherapy.
True!