GI Pharmacology and Therapeutics

GI Pharmacology and Therapeutics

• Gastroesophageal Reflux Disease (GERD) is caused by the retrograde movement of stomach contents into the esophagus due to lower esophageal sphincter (LES) dysfunction.
• Symptoms include heartburn, regurgitation, chest pain, chronic cough, and laryngitis.
• Risk factors include obesity, smoking, alcohol use, spicy foods, caffeine, citrus, chocolate, and pregnancy.
• Medications like NSAIDs, calcium channel blockers, and bisphosphonates can be triggers.
• Lifestyle modifications, like weight loss and elevating the head of the bed, are management guidelines.
• Step-up therapy involves starting with H2 blockers for mild cases and progressing to proton pump inhibitors (PPIs) for moderate to severe symptoms.
• Maintenance therapy, including long-term PPI use, is only necessary for severe erosive esophagitis or Barrett's esophagus.
• Medication choice depends on the severity and frequency of GERD symptoms.

Antacids

• Mechanism: Neutralize stomach acid.
• Examples include Tums (calcium carbonate), Maalox, and Mylanta.
• Best uses are for occasional mild heartburn and to provide short-term relief.
• Limitations include not being suitable for chronic or severe GERD, and interference with some medications' absorption.

H2 Receptor Antagonists

• Mechanism: Block histamine on parietal cells, reducing acid production.
• Examples include Famotidine (Pepcid), Ranitidine (withdrawn in many markets), and Cimetidine (Tagamet).
• Best use for mild to moderate GERD symptoms, particularly effective for nocturnal acid suppression.
• Limitations include tolerance development with long-term use and less effectiveness than PPIs for healing the lining of the esophagus.

Proton Pump Inhibitors (PPIs)

• Mechanism: Irreversibly inhibit the H+/K+ ATPase (proton pump) in parietal cells, reducing acid production.
• Examples include Omeprazole (Prilosec), Esomeprazole (Nexium), Pantoprazole (Protonix), and Lansoprazole (Prevacid).
• Best use is as a first-line treatment for moderate to severe GERD and erosive esophagitis and long-term control in chronic GERD.
• Limitations include a delayed onset of 1-4 days, risk of nutrient deficiencies, hypomagnesemia, osteoporosis, and increased risk of infections.

Prokinetic Agents

• Mechanism: Improve motility and LES tone, promoting gastric emptying.
• Examples include Metoclopramide (Reglan) and Domperidone (not available in all countries).
• Best uses for GERD with delayed gastric emptying.
• Limitations include significant side effects with Metoclopramide (e.g., tardive dyskinesia).

Alginates

• Mechanism: Form a viscous barrier that floats on stomach contents, reducing reflux.
• Examples include Gaviscon.
• Best use for symptom relief in mild GERD.

Peptic Ulcer Disease (PUD)

• Definition: Mucosal erosions in the stomach or duodenum due to acid-pepsin activity.
• Causes include H. pylori infection, NSAID use, stress, and Zollinger-Ellison Syndrome.
• Complications include bleeding, perforation, and gastric outlet obstruction.
• Management guidelines include H. pylori testing for all diagnosed with PUD, using PPI prophylaxis in high-risk patients on long-term NSAIDs, and discontinuing NSAIDs when possible.

General Treatment Principles for PUD

• Reducing gastric acid is crucial for healing and preventing further injury.
• Therapies used are the same as for GERD.
• Examples of cytoprotective agents include sucralfate and misoprostol.
• Eradication of H. pylori is crucial in H. pylori positive ulcers to prevent recurrence.
• Treatments include triple therapy (PPI + Amoxicillin + Clarithromycin) or quadruple therapy.

Anti-diarrheals

• Anti-diarrheals are used to reduce the frequency and urgency of bowel movements, manage dehydration, and increase patient comfort.
• Common conditions include acute non-infectious diarrhea, chronic diarrhea, and traveler's diarrhea.
• Medications work by slowing intestinal motility, increasing water absorption, or reducing intestinal fluid secretion.

Viral Infections

• A diverse range of viral infections affect the body.
• Various viral infections can cause inflammation in the respiratory tract, gastrointestinal tract or the eyes.
• A number of symptoms can be associated with different viral infections, like headaches, fever and inflammation in the eyes etc.
• Diagnosis and treatment of viral infections depend on the specific virus.

Antispasmodics

• Antispasmodics relieve or prevent muscle spasms in smooth muscles of the GI, urinary, or uterus.
• Types include anticholinergic agents and calcium channel blockers.
• Common conditions treated with antispasmodics include IBS, functional gastrointestinal disorders, biliary colic, diverticular disease, postoperative bowel spasms, and genitourinary spasms etc.

Promotility Agents

• Promotility agents are used to treat conditions where GI motility is slowed or impaired.
• Examples include metoclopramide and erythromycin.
• Mechanism of action includes enhancing acetylcholine release, mimicking motilin, or blocking dopamine receptors.
• Common uses for promotility agents include GERD, gastroparesis, functional dyspepsia, ileus, IBS-C, and SIBO (Small Bowel Bacterial Overgrowth).