Exam Review

Nausea and Vomiting

• Nausea: A sensation signaling the urge to vomit.

• Vomiting: The act of expelling gastric contents through the mouth, acting as a protective mechanism to rid the body of poisons.

  • Process: A forceful, involuntary bodily response triggered by impulses to the vomiting center located in the medulla of the brain.

• Causes: Signals to the vomiting center come from various areas including:

  • Chemoreceptor trigger zone

  • Cerebral cortex

  • Visceral afferents from the gastrointestinal (GI) tract.

• Complications of Vomiting:

  • Dehydration

  • Electrolyte imbalance

  • Esophageal tear

  • Malnutrition (long-term).

Antiemetics

• Treatment Goals: Aim for symptom relief and prevention of nausea and vomiting (N/V).

Antacids

• Magnesium Hydroxide & Aluminum Hydroxide

  • Decrease gastric pH (examples include 'milk of magnesia', 'Amphojel').

  • Side Effects: Diarrhea (laxative effect), constipation, potential impact on kidney function and aluminum accumulation affecting bones/brain.

• Calcium Carbonate and Sodium Citrate

  • Indications: Help with heartburn/indigestion.

  • Neutralize stomach acids but may cause rebound acidity if used long-term by stimulating excess gastrin.

• Sodium Bicarbonate

  • Caution: Use can lead to 'milk-alkali syndrome', dry mouth, confusion, and lethargy due to calcium levels increase.

  • Contraindicated in patients with hypertension, heart failure, or kidney issues.

  • Note: Can affect absorption of other medications due to changes in stomach pH.

Histamine 2 Receptor Antagonists

• Drugs: Cimetidine, Famotidine, Nizatidine, Ranitidine.

  • Mechanism of Action: Blocks acid secretion by inhibiting H2 receptors on parietal cells.

  • Indications: Treatment for heartburn/reflux.

Anticholinergics and Antihistamines

• Antihistamines (e.g., Meclizine): Block signals in the brain triggering N/V.

• Anticholinergics (e.g., Scopolamine, Hyosine): Calm nerve signals in the balance system; side effects can include drowsiness, confusion, dry mouth, and difficulty urinating (reversible with Physostigmine).

Phenothiazines and Butyrophenones

• Phenothiazines (e.g., Prochlorperazine): Block dopamine receptors to inhibit signals to the vomiting center; possible side effects include movement disorders and orthostatic hypotension.

• Butyrophenones (e.g., Droperidol): Similar action and risk of QT prolongation.

5-HT3 Serotonin Receptor Antagonists

• Drugs: Ondansetron, Granisetron, Palonosetron, Dolasetron.

  • Mechanism of Action: Blocks serotonin receptors to reduce N/V from chemotherapy or surgery.

  • Side Effects: Constipation, headache, fatigue, and potential movement disorders.

Corticosteroids

• Used in managing chemotherapy-induced N/V as part of palliative care.

• Side Effects: Increased appetite, fluid retention, insomnia, hyperglycemia, and risk of infection.

• Interactions: Increased GI bleeding with NSAIDs, hypokalemia with diuretics.

Dopamine Receptor Antagonists

• Example: Metoclopramide used for gastroparesis and prevention of N/V related to chemotherapy.

• Side Effects: Sedation, fatigue, risk of tardive dyskinesia.

  • Contraindicated: GI obstruction, perforation, hemorrhage, history of seizures, pheochromocytoma.

Substance P/Neurokinin Receptor Antagonists

• Drugs: Aprepitant, Fosaprepitant, Rolapitant.

  • Indications: Part of combination therapy for high emetogenic chemotherapy.

  • Side Effects: Fatigue, dizziness, diarrhea, and increased effects of warfarin.

Prophylaxis in Chemotherapy-Induced N/V (CINV)

• High Risk: Drugs like Cisplatin, Dacarbazine, Anthracycline.

• Moderate Risk: Carboplatin, Oxaliplatin, Irinotecan.

• Low Risk: Etoposide, Paclitaxel, Docetaxel.

• Minimal Risk: Bleomycin, Vinblastine, Fludarabine.

Combination Therapy for High Risk CINV

• Day 1: NK1 receptor antagonist + 5-HT3 antagonist + dexamethasone.

• Days 2-4: Continue dexamethasone.

Refractory N/V and Special Populations

• Pediatrics: Include oral rehydration, distraction techniques; Ondansetron for gastroenteritis.

  • Caution with antihistamines in very young children.

Diarrhea and Constipation

Diarrhea

• Definition: Increase in frequency and liquidity of stool; classified as acute (less than 2 weeks) or chronic (more than 30 days).

• Common Causes: Infectious agents, medications, increased GI motility.

  • Symptoms: Changes in stool consistency; small intestine effects may show watery stool without blood, whereas colon issues may show bloody diarrhea.

Treatment of Diarrhea

• First-Line: Diet modifications and hydration; antimotility medications like Loperamide.

• Antisecretory Agents: Bismuth subsalicylate and probiotics like Lactobacillus Rhamnosus GG.

Constipation

• Definition: Difficulty or infrequent defecation; caused by dietary factors, medication side effects.

• Types of Laxatives:

  • Bulk Forming: Psyllium, Methylcellulose which absorb water to form stool.

  • Stool Softeners: Docusate sodium helps make stool softer.

  • Irritant/Stimulant Laxatives: Bisacodyl and Senna stimulate bowel movement through nerve activation.

Gastroesophageal Reflux Disease (GERD)

Introduction

• Definition: Condition characterized by the abnormal flow of stomach acid back into the esophagus.

• Symptoms include heartburn, regurgitation, and chronic cough.

• Treatment Goals: Reduce symptoms, promote healing, and prevent complications.

Antacids

• Mechanism: Neutralize stomach acid; examples include Magnesium Hydroxide, Aluminum Hydroxide, and Sodium Bicarbonate.

• Caution: Can lead to acid rebound and may cause electrolyte imbalances.

H2 Receptor Antagonists

• Example: Cimetidine, Famotidine: reduce acid secretion and increase gastric emptying.

Peptic Ulcer Disease (PUD)

Introduction

• Causes: H. pylori infection, chronic use of NSAIDs leading to ulceration of gastric and duodenal mucosa.

• Symptoms include epigastric pain and nocturnal pain.

Treatment

• Eradication of H. pylori: PPIs and antibiotics.

• NSAID Induced Ulcers: Discontinue or reduce NSAID use; may treat with PPIs or misoprostol.

Inflammatory Bowel Disease (IBD) and Irritable Bowel Syndrome (IBS)

IBS

• Characterized by abdominal pain and altered bowel habits.

• Treatments include Lubiprostone and Linaclotide for symptom management.

IBD

• Involves Crohn’s Disease and Ulcerative Colitis characterized by inflammation of the intestinal wall.

• Treatments for IBD: Include corticosteroids, antimicrobials, immunosuppressives, and biologics.

  • Monitor for infection risk with immunosuppressive agents.