Pharmacology of Antacids

Proton Pump Inhibitors (PPIs)

• Mechanism of action: Inhibit the H+/K+ ATPase enzyme in gastric parietal cells, reducing acid secretion
• Examples:
  • Omeprazole
  • Lansoprazole
  • Rabeprazole
  • Esomeprazole
  • Pantoprazole
• Indications:
  • Gastroesophageal reflux disease (GERD)
  • Peptic ulcer disease
  • Zollinger-Ellison syndrome
  • NSAID-induced ulcers
• Adverse effects:
  • Headache
  • Diarrhea
  • Abdominal pain
  • Increased risk of Clostridioides difficile infection

H2 Blockers (Histamine-2 Antagonists)

• Mechanism of action: Bind to H2 receptors on gastric parietal cells, reducing acid secretion
• Examples:
  • Ranitidine
  • Famotidine
  • Nizatidine
  • Cimetidine
• Indications:
  • Peptic ulcer disease
  • GERD
  • Zollinger-Ellison syndrome
• Adverse effects:
  • Headache
  • Dizziness
  • Constipation
  • Impotence (cimetidine)

Antacids

• Mechanism of action: Neutralize stomach acid by increasing pH
• Examples:
  • Sodium bicarbonate
  • Magnesium hydroxide (Mylanta)
  • Aluminum hydroxide (Amphojel)
  • Calcium carbonate (Tums)
• Indications:
  • Heartburn
  • Indigestion
  • Upset stomach
• Adverse effects:
  • Diarrhea (magnesium-containing antacids)
  • Constipation (aluminum-containing antacids)
  • Interactions with other medications (e.g., tetracycline)

Gastroprotective Agents

• Mechanism of action: Protect the gastric mucosa from injury
• Examples:
  • Sucralfate
  • Misoprostol
• Indications:
  • Prevention of NSAID-induced ulcers
  • Treatment of duodenal ulcers
• Adverse effects:
  • Constipation (sucralfate)
  • Diarrhea (misoprostol)

Anti-secretory Therapy

• Goal: Reduce acid secretion to promote healing of peptic ulcers and prevent recurrence
• Combination therapy:
  • PPIs or H2 blockers + antibiotics (e.g., clarithromycin, amoxicillin) for Helicobacter pylori eradication
  • PPIs or H2 blockers + gastroprotective agents for NSAID-induced ulcers

Proton Pump Inhibitors (PPIs)

• Inhibit H+/K+ ATPase enzyme in gastric parietal cells, reducing acid secretion
• Examples: omeprazole, lansoprazole, rabeprazole, esomeprazole, pantoprazole
• Used to treat: Gastroesophageal reflux disease (GERD), peptic ulcer disease, Zollinger-Ellison syndrome, NSAID-induced ulcers
• Adverse effects: headache, diarrhea, abdominal pain, increased risk of Clostridioides difficile infection

H2 Blockers (Histamine-2 Antagonists)

• Bind to H2 receptors on gastric parietal cells, reducing acid secretion
• Examples: ranitidine, famotidine, nizatidine, cimetidine
• Used to treat: peptic ulcer disease, GERD, Zollinger-Ellison syndrome
• Adverse effects: headache, dizziness, constipation, impotence (cimetidine)

Antacids

• Neutralize stomach acid by increasing pH
• Examples: sodium bicarbonate, magnesium hydroxide (Mylanta), aluminum hydroxide (Amphojel), calcium carbonate (Tums)
• Used to treat: heartburn, indigestion, upset stomach
• Adverse effects: diarrhea (magnesium-containing antacids), constipation (aluminum-containing antacids), interactions with other medications (e.g., tetracycline)

Gastroprotective Agents

• Protect gastric mucosa from injury
• Examples: sucralfate, misoprostol
• Used to: prevent NSAID-induced ulcers, treat duodenal ulcers
• Adverse effects: constipation (sucralfate), diarrhea (misoprostol)

Anti-secretory Therapy

• Goal: reduce acid secretion to promote healing of peptic ulcers and prevent recurrence
• Combination therapy: PPIs or H2 blockers + antibiotics for Helicobacter pylori eradication, PPIs or H2 blockers + gastroprotective agents for NSAID-induced ulcers

Heartburn Relief

• Antacids neutralize stomach acid to relieve heartburn symptoms, providing quick relief within minutes
• Antacids can be taken as needed or on a regular schedule to prevent heartburn

Histamine-2 Blockers

• Histamine-2 (H2) blockers reduce acid production in the stomach to treat heartburn, acid reflux, and GERD
• Examples of H2 blockers include ranitidine (Zantac) and famotidine (Pepcid)
• H2 blockers take longer to start working than antacids but provide longer-lasting relief

Acid Reflux Treatment

• Antacids may not be effective for severe acid reflux symptoms
• Combination therapy with H2 blockers or PPIs may be needed for more severe acid reflux
• Lifestyle changes, such as avoiding trigger foods and losing weight, can alleviate acid reflux symptoms

Antacid Side Effects

• Common antacid side effects include diarrhea, constipation, bloating, gas, stomach cramps, nausea, and vomiting
• Rare but serious side effects include kidney stones, interactions with other medications, high blood pressure, and heart problems

Proton Pump Inhibitors (PPIs)

• PPIs block stomach acid production to treat severe acid reflux, GERD, and stomach ulcers
• Examples of PPIs include omeprazole (Prilosec) and lansoprazole (Prevacid)
• PPIs are more effective than antacids or H2 blockers but may have more side effects and interactions with other medications

This quiz covers the mechanism of action, indications, and adverse effects of Proton Pump Inhibitors (PPIs) and H2 Blockers in pharmacology.