Gastrointestinal System

Antiulcer Pharmacology Overview

Antacids

• Action:

  • Neutralize gastric hydrochloric acid (HCl)

  • Increase gastric pH

  • Decrease gastric acidity, reducing irritation of the mucosa

Indications

• Primary Indications:

  • Hyperacidity

  • Heartburn

  • Acid indigestion

  • Acid reflux

  • Gastroesophageal Reflux Disease (GERD)

  • Peptic Ulcer Disease (PUD)

• Additional Indications:

  • Electrolyte imbalance related to low magnesium or calcium

  • Hyperphosphatemia (certain aluminum-based antacids bind phosphate)

  • Calcium supplementation (calcium carbonate)

  • Magnesium deficiency (magnesium-containing antacids)

Goals of Antacid Therapy

• Reduce pain and discomfort

• Increase gastric pH (normal gastric pH ≈ 1.5–3.5)

• Reduce acidity to decrease irritation of gastric and esophageal mucosa

Antacid Drugs

• Types of Antacids:

  • Magnesium hydroxide (Milk of Magnesia)

  • Aluminum carbonate (Basaljel)

  • Aluminum phosphate (Phosphagel)

  • Aluminum hydroxide (Amphojel)

  • Calcium carbonate (Tums)

  • Sodium bicarbonate (Alka Seltzer)

• Combination Products:

  • Maalox

  • Mylanta

  • Gaviscon

Adverse Effects of Antacids

• Side Effects:

  • Magnesium: leads to diarrhea

  • Aluminum: leads to constipation

  • Calcium: may cause constipation and possible rebound acidity

  • Sodium bicarbonate: can cause fluid retention and metabolic alkalosis

• Commonly Noted Effects:

  • Interference with drug absorption

  • Altered bowel patterns

Nursing Implications for Antacids

• Administration:

  • Differences between suspension and solid forms

  • Relationship to other drugs

• Monitoring:

  • Stool changes

  • Over-the-counter (OTC) concerns

  • Electrolyte levels

H2 Blockers / Antisecretory Agents

• Action:

  • Block H2 receptors on parietal cells

  • Decrease volume and acidity of gastric secretions

  • Reduce both daytime and nocturnal acid production

Indications for H2 Blockers

• Short-term treatment (4-8 weeks)

• Hypersecretory conditions:

  • Peptic Ulcer Disease (PUD)

  • Gastroesophageal Reflux Disease (GERD)

H2 Blocker Medications

• Drugs:

  • Cimetidine (Tagamet)

  • Famotidine (Pepcid)

  • Nizatidine (Axid)

• Dosage Example:

  • Cimetidine Injection: 300 mg/2 mL for I.M. or I.V. use (must be diluted for I.V.)

  • Famotidine: oral suspension 400 mg constituted to 50 mL (40 mg per 5 mL)

Adverse Effects of H2 Blockers

• Side Effects:

  • CNS: dizziness, drowsiness, headache, confusion (higher risk in elderly or renally impaired)

  • GI: diarrhea or constipation

  • Cardiac: rare cases of arrhythmias, decreased blood pressure (with I.V. use)

  • Musculoskeletal/Skin: skin rash, muscle pain

  • Drug specific: greater occurrence of gynecomastia and impotence with cimetidine

• Additional Adverse Effects:

  • Hematologic: rare decrease in bone marrow (RBC, WBC, platelets)

  • Endocrine: males may experience decreased sperm count, impotence, and gynecomastia

Interactions and Contraindications

• Drug Interactions:

  • Cigarettes, CNS depressants, antiarrhythmics, methylxanthines, warfarin, phenytoin, tricyclic antidepressants

• Contraindications:

  • Known hypersensitivity

  • Pregnancy/Lactation (use caution)

  • Severe liver disease

  • Severe kidney disease

  • Allergy testing

  • Gastric acid testing

  • Acute porphyria

  • Situations where reduced acidity may mask serious gastric issues

Nursing Implications for H2 Blockers

• Administration:

  • Oral: Provide with food (except nizatidine)

  • IM: Deep muscle injection

  • IV infusion: Monitor vital signs

• Monitoring:

  • CNS depression and mood changes

  • Bleeding

  • Foods to avoid

  • Gynecomastia resolution

  • Effects of smoking, which reverses drug efficacy

Proton Pump Inhibitors (PPIs)

• Action:

  • Suppress gastric acid secretion

  • Block the final step in production of HCl

  • Bind with enzymes in gastric acid production (Hydrogen, Potassium, and Adenosine Triphosphatase)

Indications for PPIs

• Peptic Ulcer Disease (PUD)

• Gastroesophageal Reflux Disease (GERD)

• Treatment of Helicobacter Pylori

PPI Medications

• Common Drugs:

  • Omeprazole (Prilosec)

  • Lansoprazole (Prevacid)

  • Esomeprazole (Nexium)

  • Pantoprazole (Protonix)

  • Rabeprazole (Aciphex)

Adverse Effects of PPIs

• Potential Adverse Effects:

  • Gastrotoxicity

  • Hypersensitivity reactions

• Additional Effects:

  • Respiratory complications

  • CNS issues

  • Muscular problems

Nursing Implications for PPIs

• Oral Administration:

  • Take on an empty stomach

  • For sustained-release capsules, sprinkle on applesauce

  • Specific procedures for lansoprazole via NGT (nasogastric tube) should be consulted in the procedure manual

Treatment for H. Pylori

• Pylera Pack:

  • Contains: Bismuth (Pepto-Bismol), tetracycline (antibiotic), and metronidazole (Flagyl - antibiotic commonly used for C. diff)

• Administered with a PPI (e.g., omeprazole)

• Duration: 10 - 14 days

Cytoprotective Agents

• Drug: Sucralfate (Carafate)

• Action:

  • Forms a complex that adheres to the ulcer crater

  • Protects the ulcer from irritation

Indications for Sucralfate

• Short-term treatment (4 to 8 weeks)

• Mainly for Peptic Ulcer Disease (PUD) and Gastroesophageal Reflux Disease (GERD)

Dosage and Adverse Effects of Sucralfate

• Dosage:

  • Typical dosing: 1g, 4 times daily (before meals and at bedtime)

• Adverse Effects:

  • Constipation

  • Dry mouth

  • Dizziness

Nursing Implications for Sucralfate

• Administration:

  • Must be given on an empty stomach

  • Decreases absorption of most drugs; should be administered 1 - 2 hours before or after other medications

  • Antacids should be spaced by ½ hour before or after sucralfate

  • H2 blockers should also be spaced by ½ hour before or after

• Prophylactic Treatment: Watch for constipation

Prostaglandins

• Action:

  • Protect the mucosal surface of the stomach

• Indications:

  • Prophylaxis related to ASA and NSAID use

• Drug: Misoprostol (Cytotec)

• Dosage: 100 - 200 mcg four times daily

Adverse Effects of Misoprostol

• Common Side Effects:

  • Abdominal pain

  • Diarrhea

  • Flatulence

  • Increased uterine contractions

  • Vaginal bleeding

• Contraindication: Pregnancy

Nursing Implications for Misoprostol

• Precautions:

  • Require a pregnancy test before administration

  • For those of childbearing age, use contraception

  • Administer with food to reduce cramping

  • Diarrhea typically resolves within one week

GI Quick Guide: High-Yield Summary

• Administration Guidelines:

  • Antacids: Administer 1–3 hours post meals and at bedtime; provide spacing of 1–2 hours from other medications.

  • H2 Blockers: Administer with food; note nizatidine can be taken without food.

  • PPIs: Administer 30–60 minutes before breakfast, do not crush enteric-coated beads.

  • Sucralfate: Administer on an empty stomach, before meals and at bedtime.

  • Misoprostol: Administer with food to minimize discomfort.

• Monitoring Requirements:

  • Monitor electrolytes (Mg for PPIs, Ca and phosphate for Al/Mg antacids).

  • Monitor renal function: Avoid Mg/Al antacids in chronic kidney disease (CKD).

  • Monitor blood pressure and heart rate with I.V. H2 blockers.

  • Monitor pregnancy status for misoprostol.

• Alerts:

  • Avoid sodium bicarbonate in patients with heart failure (HF) and hypertension (HTN).

  • Be cautious with cimetidine regarding CNS changes in the elderly and renal impaired.

  • Misoprostol poses a serious risk of uterine contractions; it is contraindicated during pregnancy.

  • Long-term use of PPIs may lead to risks such as fractures and low magnesium levels.

• Common Misunderstandings:

  • PPIs do not provide instant relief; they require several days to achieve full effect.

  • Antacids may interfere with the absorption of several other drugs.

  • Proper administration timing for sucralfate is crucial to avoid absorption issues.

  • H2 blockers do not neutralize acid; instead, they reduce production, unlike antacids.

NCLEX High-Priority Safety & Red Flags for GI Medications

• Safe Administration Techniques:

  • Time PPIs prior to meals; do not crush delayed-release beads.

  • Maintain appropriate timing for antacids and sucralfate in relation to other medications.

  • Infuse I.V. H2 blockers slowly to prevent hypotension or arrhythmias.

• Red Flags and Required Actions:

  • Observing melena, hematemesis, or severe epigastric pain warrant evaluation for possible GI bleeding.

  • Any new confusion in patients on cimetidine indicates the need to assess renal function and consider alternatives.

  • Persistent reflux symptoms when using antacids alone require escalation of treatment to H2 blockers or PPIs and evaluation of the condition.

  • Severe diarrhea following magnesium-containing antacids or misoprostol necessitates re-evaluation of therapy and hydration status.

• Significant Drug Interactions:

  • Cimetidine increases levels of warfarin, phenytoin, and theophylline.

  • PPIs may reduce the absorption of certain antifungals and can interact with clopidogrel; pantoprazole is the preferred PPI in those cases.

  • Sucralfate may reduce the absorption of digoxin, warfarin, levothyroxine, and fluoroquinolones.

• High-Risk Populations:

  • Chronic kidney disease (CKD) patients should avoid magnesium and aluminum antacids to prevent accumulation risks.

  • Patients with heart failure and hypertension should avoid sodium bicarbonate due to the risk of fluid retention.

  • Pregnancy is an absolute contraindication for misoprostol.

  • Elderly patients face increased risks of CNS effects when using H2 blockers.

Study Smart: GI Pharmacology Focus Points

• Essential Focus Areas:

  • Understand medication timing rules: ensuring appropriate spacing for antacids, taking PPIs before meals, and administering sucralfate on an empty stomach.

  • Recognize mechanisms of action: antacids neutralize acid; H2 blockers reduce acid secretion; PPIs block the final production step of gastric acid.

  • Be aware of common electrolyte patterns and their implications: magnesium can cause diarrhea, aluminum and calcium may lead to constipation, and sodium can cause fluid retention.

  • Understanding misoprostol's pregnancy risks is essential for safe practice.

  • Remember that sucralfate acts as a barrier rather than suppressing acid production.

• Areas to Avoid Excessive Focus:

  • Don't focus extensively on minor brand name differences.

  • Avoid overly detailed study of rare side effects that are unlikely to affect clinical decisions.

  • Skip mechanism details that exceed the Licensed Practical Nurse (LPN) scope of practice.

• Pattern Recognition:

  • Identify chronic NSAID users as candidates for misoprostol prophylaxis.

  • Be prepared to elevate treatment to H2 blockers or PPIs following recurrent symptoms with antacids.

  • Understand that the irreversible nature of PPI pump inhibition explains the delayed full therapeutic effect of these agents.

  • Recognize that elderly patients with renal impairment are at higher risk for CNS effects when using H2 blockers.