Drugs Affecting the GI

Question 1

Peptic Ulcer Disease: Helicobacter Pylori

Answer 1

A major causative factor (60% of gastric and up to 90% of duodenal ulcers) is chronic inflammation due to Helicobacter pylori
H. pylori colonization increases gastrin secretion
Gastrin stimulates the production of gastric acid by parietal cells

Question 2

Peptic Ulcer Disease: NSAIDs

Answer 2

Block the function of cyclooxygenase 1 (cox-1), which is essential for the production of prostaglandins (they cause pain, but necessary in the stomach).
The gastric mucosa protects itself from gastric acid with a layer of mucus, the secretion of which is stimulated by certain prostaglandins

Question 3

GERD

Answer 3

incompetence of the lower esophageal sphincter
transient lower esophageal sphincter relaxation
hiatal hernia

Tendency of excessive and acidic stomach contents to back up, or reflux, into the lower and even upper esophagus

Question 4

Antacids: Mechanism of Action

Answer 4

Increase gastric pH to neutralize stomach acid
Promote gastric mucosal defense mechanisms
They do this by stimulating the secretion of:
Mucus: protective barrier against HCl
Bicarbonate: helps buffer acidic properties of stomach
Antacids DO NOT prevent the overproduction of acid
Antacids neutralize the acid once it is in the stomach

Question 5

Antacids: Drug Effects

Answer 5

Reduction of pain associated with acid-related disorders is the primary drug effect

Reducing acidity reduces pain

Question 6

Antacids: Aluminum Salts

Answer 6

Have constipating effects
Often used with magnesium to counteract constipation
Often recommended for patients with renal disease (more easily excreted via the colon)

Examples
Aluminum carbonate: Basaljel
Hydroxide salt: AlternaGEL
Combination products (aluminum hydroxide and magnesium hydroxide): Maalox

Question 7

Antacids: Magnesium Salts

Answer 7

Commonly cause diarrhea; usually used with other drugs to counteract this effect
Osmotic laxative
Dangerous when used with renal failure—the failing kidney cannot excrete extra magnesium, resulting in accumulation

Examples:
Combination products such as Maalox, Mylanta (aluminum and magnesium)
Hydroxide salt: magnesium hydroxide (MOM)

CRUCIAL: to have healthy kidneys

Question 8

Antacids: Calcium Salts

Answer 8

Forms: many, but carbonate is most common
High acid-neutralizing capacity
May cause constipation, kidney stones, flatulence
Often advertised as an extra source of dietary calcium
More for prevention of GERD, upset stomach, not PUD

Example:
Tums (calcium carbonate)

Question 9

Antacids: Sodium Bicarbonate

Answer 9

Highly acid-neutralizing capacity
Buffers the acidic properties of HCl
Quick onset, but short duration
May cause metabolic alkalosis
Sodium content may cause problems in patients with CHF,  hypertension, or renal insufficiency (Not recommended for sodium-restricted diets

Examples:
Bicarbonate Salt: Alka-Seltzer

Question 10

Antacids: Adverse Effects

Answer 10

Aluminum and calcium: Constipation
Magnesium: Diarrhea
Calcium Carbonate: Produces gas and belching; often combined with simethicone

Question 11

Antacids: Drug Interactions

Answer 11

1.) Absorption of other drugs to antacids
Reduces the ability of the other drug to be absorbed into the body

2.) Chelation
Chemical binding, or inactivation, of another drug
Produces insoluble complexes
Result: reduced drug absorption

3.) Increased stomach pH
Increased absorption of basic drugs
Decreased absorption of acidic drugs

4.) Increased urinary pH
Increased excretion of acidic drugs
Decreased excretion of basic drugs

Question 12

Antacids: Nursing Implications

Answer 12

Assess for allergies and pre-existing conditions that may restrict the use of antacids, such as:
Hypertension 
Renal Disease
Electrolyte Imbalances
HF 	

Patients with HF or hypertension should not use antacids with high sodium content
Use with caution with other medications due to the many drug interactions
Take 2 hrs after other drugs, 1 hour after meals and at bedtime
Long-term self-medication with antacids may mask symptoms of serious underlying diseases, such as cancer or bleeding ulcers

Question 13

H2 Antagonists

Answer 13

Block histamine at the (H2) receptors of acid-producing parietal cells
Production of hydrogen ions is reduced, resulting in decreased production of HCl

Suppressed acid secretion in the stomach

Question 14

Histamine

Answer 14

Histamine is a substance that performs many functions:
It is involved in nerve impulse transmission, dilation of capillaries, contraction of smooth muscles, stimulation of gastric secretion, and acceleration of heart rate

Two types of histamine receptors
H1 (histamine1): mediate smooth muscle contractions and dilation of capillaries (causes vasodilation)
H2 (histamine2): mediates gastric acid secretion

Question 15

H2 Antagonists: Adverse Effects

Answer 15

Cimetidine may induce impotence and gynecomastia
May also see:
Headaches, constipation, diarrhea, N/V, rash, other effects
Leukopenia, granulocytopenia, thrombocytopenia - rare
Confusion in elderly

Question 16

H2 Antagonists: Drug Interactions

Answer 16

Cimetidine
Binds with P-450 microsomal oxidase system in the liver, resulting in inhibited oxidation of many drugs and increased drug levels

All H2 antagonists may inhibit the absorption of drugs that require an acidic GI environment for absorption (empty stomach)

SMOKING has shown to decrease the effectiveness of H2 blockers (causes hyperacidity of the stomach)

Question 17

H2 Antagonists: Nursing Implications

Answer 17

Assess for allergies and impaired renal or liver function
Use with caution in patients who are confused, disoriented, or elderly (especially cimetidine)
For intravenous doses (famotidine), follow administration guidelines
Take 2 hours before or after antacids

Question 18

Proton Pump Inhibitors

Answer 18

The parietal cells release positive hydrogen ions (protons) during HCl production
This process is called the “proton pump”
H2 blockers and antihistamines do not stop the action of this pump

Examples:
Total inhibition of gastric acid secretion
lansoprazole (Prevacid)
omeprazole (Prilosec)
rabeprazole (Aciphex)
pantoprazole (Protonix) (IV form available)
esomeprazole (Nexium)

-Prazole: proton pump inhibitors

Question 19

Mechanism of Action of PPI’s

Answer 19

Irreversibly binds to H+/K+ ATPase enzyme system
This bond prevents the movement of hydrogen ions from the parietal cells into the stomach
Result: ALL gastric acid secretion is temporarily blocked
In order to return to normal acid secretion after PPI’s have been stopped, the parietal cell must synthesize new H+/K+ ATPase

Question 20

Indications for PPI’s:

Answer 20

GERD maintenance therapy
Erosive esophagitis
Short-term treatment of active duodenal and benign gastric ulcers

Treatment of H. pylori–induced ulcers
Given usually with an antibiotic

Question 21

Adverse Effects of PPI’s

Answer 21

Headache: H/A
Diarrhea
C-diff???

Pneumonia (aspiration: stomach is no longer acidic, bacteria colonizes)

Question 22

Nursing Implications of PPI’s

Answer 22

Assess for allergies and history of liver disease
Extensively metabolized by p-450 system

*Pantoprazole (Protonix) is the only proton pump inhibitor available for parenteral administration, and can be used for patients who are unable to take oral medications

May increase serum levels of diazepam, phenytoin, and cause increased chance for bleeding with warfarin

PPIs often work best when taken 1 hour before meals

Question 23

Sucralfate (Carafate)

Answer 23

*Cytoprotective drug and used for stress ulcers, PUD
medication that combats ulcers not by reducing gastric acid but by increasing mucosal protection

Attracted to and binds to the base of ulcers and erosions, forming a protective barrier over these areas, like a piece of gum

Protects these areas from pepsin, which normally breaks down proteins (making ulcers worse)

Question 24

Sucralfate cont.d

Answer 24

Little absorption from the gut
Do not administer with other medications
May impair absorption of other drugs—give other drugs at least 1 hour before or after Sucralfate
Most common adverse effect: constipation
Binds with phosphate; may be used in chronic renal failure to reduce phosphate levels

Question 25

Misoprostol (Cytotec)

Answer 25

Synthetic prostaglandin analog Prostaglandins have cytoprotective activity Protect gastric mucosa from injury by enhancing local production of mucus or bicarbonate Promote local cell regeneration Help to maintain mucosal blood flow *Used for prevention of NSAID-induced gastric ulcers Most common adverse effects: diarrhea, abdominal pain *Pregnancy category X: causes premature labor

Question 26

Prokinetic Agents

Answer 26

The prokinetic agents increase the effect of acetylcholine on the GI system. Stimulates motility w/o stimulating GI secretion Acetylcholine is responsible for normal GI function. Prokinetic agents increase peristalsis and gastric emptying. Used for Diabetics to absorb/eliminate a meal. Prototype drug: metoclopramide (Reglan).

Question 27

Metoclopramide

Answer 27

Pharmacotherapeutics Relieve symptoms of diabetic gastroparesis. Empties stomach. Used IV to prevent N/V. Blocks dopamine/serotonin in brain associated with N/V Assistance with gastric tube insertion, increase motility of tube - single dose Pharmacodynamics Mechanism of action is unclear Appears to sensitize tissues to effect of acetylcholine Increases peristalsis of Upper GI tract Blocks CTZ receptors (dopamine/serotonin)—antiemetic effect

Question 28

Metoclopramide cont.d

Answer 28

Contraindications and precautions GI hemorrhage, perforation, or mechanical obstruction Adverse effects Restlessness, drowsiness, depression, insomnia, headache, anxiety, dizziness, and confusion Drug interactions Levodopa (Dopamine replacement for Parkinson’s), anticholinergics (works like acetylcholine), and narcotics Used short term; movement issues like Parkinson’s if used long term (blocking dopamine) Maximizing therapeutic effects Give oral doses 30 minutes before each meal. Do not administer metoclopramide concurrently with anticholinergic drugs. Minimizing adverse effects Monitor for evidence of depression. Withhold the dose and notify the prescriber if Parkinson-like symptoms occur.

Question 29

To promote the optimal effectiveness of the drug, metoclopramide should be given:

Answer 29

30 minutes before meals | Metoclopramide should be given 30 minutes before meals to achieve maximum effectiveness.

Question 30

Antiemetics

Answer 30

Nausea and vomiting related to oncologic therapy is frequently difficult to manage. Antiemetics, which suppress stimulation of the CTZ (Chemoreceptor Trigger Zone) are used to treat nausea and vomiting. Antiemetic drugs are primarily from three main drug classifications—selective serotonin receptor antagonists, antidopaminergic drugs, and anticholinergic drugs. Selective Serotonin Receptor Antagonists Prevent the stimulation of type 3 serotonin receptors in the CTZ. Prototype drug: ondansetron (Zofran)

Question 31

Ondansetron

Answer 31

Pharmacotherapeutics Prevent nausea and vomiting associated with cancer chemotherapy. Pharmacokinetics Metabolism: liver. Excreted: kidneys. Pharmacodynamics Blocks serotonin receptor sites in the CTZ , thus preventing nausea and vomiting. Contraindications and precautions Hypersensitivity Adverse effects Headache, constipation, and malaise Drug interactions Drugs metabolized by the cytochrome P-450 enzymes

Question 32

Disorders Affecting Lower GI Tract

Answer 32

``` Flatus: Flatulence Diarrhea Constipation Irritable bowel syndrome (IBS) Inflammatory bowel disease (IBD): Crohn’s and Ulcerative Colitis ```

Question 33

Antiflatulents

Answer 33

Used to relieve the painful symptoms associated with gas Several drugs are used to bind or alter intestinal gas and are often added to antacid combination products OTC antiflatulents Simethicone: most common Charcoal

Question 34

Simethicone

Answer 34

Antiflatulent drug Used to reduce the discomforts of gastric or intestinal gas (flatulence) Alters surface tension of gas bubbles, forming larger bubbles that can be eliminated more easily Result is decreased gas pain and increased expulsion via mouth or rectum

Question 35

Antidiarrheal Mechanisms of Action: Adsorbents

Answer 35

Coat the walls of the GI tract Bind to the causative bacteria or toxin, which is then eliminated through the stool Examples: bismuth subsalicylate (Pepto-Bismol contains aspirin, Kaopectate), kaolin-pectin (Kaopectolin) Constipation, dark stools Hearing loss, tinnitus, metallic taste

Question 36

Antimotility drugs: opiates

Answer 36

Decrease bowel motility and relieve rectal spasms Decrease transit time through the bowel, allowing more time for water and electrolytes to be absorbed Reduce pain by relief of rectal spasms Examples: loperamide (OTC: Imodium), diphenoxylate HCl w/ atropine sulfate (Lomotil)

Question 37

Adverse Effects of Antimotility drugs: opiates

Answer 37

``` Drowsiness, sedation, dizziness, lethargy Nausea, vomiting, anorexia, constipation *Respiratory depression Bradycardia, palpitations, hypotension Urinary retention Flushing, rash, urticaria ```

Question 38

Antidiarrheals: Interactions

Answer 38

Adsorbents cause increased bleeding time and bruising when given with anticoagulants Adsorbents decrease the absorption of many drugs, including digoxin, clindamycin, quinidine, hypoglycemic drugs, others

Question 39

Nursing Implications of Antidiarrheals

Answer 39

Obtain thorough history of bowel patterns, general state of health, and recent history of illness or dietary changes, and assess for allergies *DO NOT give bismuth subsalicylate to children or teenagers with chickenpox or viral illness because of the risk of Reye’s syndrome (Seizure activity) Assess fluid volume status, I&O, and mucous membranes before, during, and after initiation of treatment Teach patients to notify their physician immediately if symptoms persist Monitor for therapeutic effect

Question 40

Constipation

Answer 40

Abnormally infrequent and difficult passage of feces through the lower GI tract Symptom, not a disease Disorder of movement through the colon and/or rectum Can be caused by a variety of diseases or drugs

Question 41

Bulk-forming laxatives

Answer 41

Act similar to fiber found in diets (high fiber) Ex: Psyillium (metamucil) Absorb water to increase bulk Ex: methylcellulose (Citrucel) Distend bowel to initiate reflex bowel activity Ex: polycarbophil (Fibercon)

Question 42

Emollient

Answer 42

Stool softeners and lubricants Promote more water and fat in the stools Lubricate the fecal material and intestinal walls Ex: Stool softeners: docusate salts (Colace, Surfak) Lubricants: mineral oil

Question 43

Hyperosmotic

Answer 43

Increased oncotic pressure in the colon draws water into the stool Result: bowel distention, increased peristalsis, and evacuation Ex: Lactulose (can be used as an enema, for hepatic issues metabolizing ammonia) glycerin

Question 44

Saline

Answer 44

Increase osmotic pressure within the intestinal tract, causing more water to enter the intestines Result: bowel distention, increased peristalsis, and evacuation Ex: magnesium sulfate (Epsom salts), Sodium phosphate (Fleet enema), Magnesium hydroxide (MOM), Magnesium citrate

Question 45

Stimulant

Answer 45

Increases peristalsis via intestinal nerve stimulation | Ex: castor oil, cascarra, senna, bisacodyl

Question 46

Bulk forming laxatives Adverse Effects

Answer 46

Impaction | Fluid overload? Pt should be taking high fluids with bulk-forming

Question 47

Emollient Adverse Effects

Answer 47

Skin rashes Decreased absorption of fat- soluble vitamins Risk for bleeding if Vit K def.

Question 48

Hyperosmotic Adverse Effects

Answer 48

Abdominal bloating | Rectal irritation

Question 49

Saline Adverse Effects

Answer 49

``` Magnesium toxicity (with renal insufficiency) Cramping Electrolyte imbalances Diarrhea Increased thirst ```

Question 50

Stimulant Adverse Effects

Answer 50

Nutrient malabsorption Rectal irritation Electrolyte imbalances Gastric and rectal irritation