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Drugs Affecting the digestive system

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Sandy Kaminski

on 5 December 2013

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Transcript of Drugs Affecting the digestive system

Drugs Affecting the Digestive System
Chapters 56, 59, 62
By Sandy Kaminski

Chapter 56:
Physiology of
the Digestive System


Oral cavity
Esophagus
Stomach
Small intestine
Large intestine
Pancreas
Gallbladder
Liver

The organs of the digestive system
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

Pancreatic juices

amylase
lipase
trypsin and chymotrypsin

Mucus
Digestive enzymes
Hydrochloric acid
Electrolytes

Bile

Bile
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 - T or F
The sympathetic nervous system (fight or flight) increases gastric motility and secretions.

True
False
GI secretions can break down medications so they can be absorbed or they may destroy the medications.

Chapter 59:Drugs Used for Peptic Ulcer (PUD) and Acid Reflux Disorders (GERD)
ANTACIDS
PROTON PUMP INHIBITORS
H-Pylori Agents
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.

(Peptic Ulcer Disease) PUD results from
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

Attributed to an imbalance between cell-destructive and cell-protective effects

Such as
gastric acid
Pepsin
H. pylori infection
NSAIDs
Stress
Cigarette smoking




GASTROESOPHAGEAL
REFLUX DISEASE
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, anticholinergics, 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 intestine 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 inhibits 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

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 - T or F
Risk factors for PUD include stress, NSAID ingestion, Helicobacter pylori infection, and cigarette smoking.

True
True
False
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.

Chapter 62 - Anti-emetics
Defintions
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
Nausea and/or Vomiting
Occurs when the vomiting centre (VC) or chemoreceptor trigger zone (CTZ) are stimulated

Mechanism of Action
Block 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

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

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

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

Question – T or F
True
False
The benzodiazapine antianxiety drugs are used as anti-emetics in multidrug regimens to prevent nausea and vomiting associated with chemotherapy.

Thanks for Listening!
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