Acid reducing medications Notes

NOTES NOTES ACID REDUCING MEDICATIONS H2-RECEPTOR ANTAGONISTS (H2RAs) Figure 1.1 H2-receptor antagonists: mechanism of action. WHAT ARE THEY? TYPES Cimetidine (Tagamet): PO, IM, IV Famotidine (Pepcid): PO, IV Nizatidine (Axid): PO RaNITIdine (Zantac): PO, IM, IV Mechanism of action ▪ Competitive, reversible inhibition of parietal cell H2 receptors → ↓ H+ secretion → ↓ gastric acid production ▪ ▪ ▪ ▪ Key points ▪ Safe, rare side effects ▪ Less effective than proton pump inhibitors (PPIs) Common indications ▪ Peptic ulcers, ulcer/stress ulcer prophylaxis, gastroesophageal reflux disease (GERD), Zollinger–Ellison syndrome OSMOSIS.ORG 1

CLINICAL CONCERNS ADVERSE EFFECTS ▪ Headache, fatigue, myalgias; diarrhea, constipation Drug-specific adverse effects ▪ Cimetidine: anti-androgenic effects → gynecomastia, ↓ libido, impotence, alopecia; confusion, dizziness (crosses blood-brain barrier) ▪ Cimetidine, raNITIdine: compete with creatinine for renal tubular secretion → ↓ renal excretion of creatinine → ↑ serum creatinine DISEASE-RELATED CONCERNS ▪ Renal impairment: dosage reduction ADMINISTRATION ▪ Take 1hr before meals/other drugs; take at bedtime if once/day PREGNANCY/BREASTFEEDING IMPLICATIONS ▪ Avoid during pregnancy/breastfeeding unless necessary ▫ Pregnancy: RaNITIdine preferred ▫ Breastfeeding: famotidine preferred (↓ breast milk concentration) Figure 1.2 H2RAs: common drug-drug interactions. 2 OSMOSIS.ORG

Gastrointestinal Acid Reducing Medications Figure 1.3 H2RAs: pharmacokinetic interactions. Figure 1.4 H2RAs: general adult dosing guidelines. *Dosage varies depending on condition type/severity, dosing interval, individual characteristics OSMOSIS.ORG 3

PROTON PUMP INHIBITORS (PPIs) Figure 1.5 Proton pump inhibitors: mechanism of action. WHAT ARE THEY? Mechanism of action ▪ Irreversibly bind to parietal cell H+/K+ ATPase → ↓ gastric acid secretion Key points ▪ Prodrugs, require activation ▪ Omeprazole: CYP 2C19 inhibitor TYPES ▪ ▪ ▪ ▪ ▪ Dexlansoprazole (Dexilant): PO Esomeprazole (NexIUM): PO, IV Lansoprazole (Prevacid): PO Omeprazole (PriLOSEC): PO Pantoprazole (Protonix): PO, IV Common indications ▪ Peptic ulcers, ulcer prophylaxis, gastroesophageal reflux (GERD), Zollinger– Ellison syndrome, triple/quadruple therapy component for Helicobacter pylori eradication 4 OSMOSIS.ORG CLINICAL CONCERNS ADVERSE EFFECTS ▪ GI: nausea, abdominal pain, diarrhea; ↓ absorption of iron, calcium, magnesium, vitamin B12 ▪ Miscellaneous: headache; rashes; ↑ risk of osteoporosis ▪ Infections: ↑ risk of Clostridioides difficile infection, pneumonia ADMINISTRATION ▪ Administer 1hr before meals/other drugs; take at bedtime if once/day

Gastrointestinal Acid Reducing Medications Figure 1.6 PPIs: common drug-drug interactions. Figure 1.7 PPIs: pharmacokinetic interations. OSMOSIS.ORG 5

Figure 1.8 PPIs: general adult dosing guidelines. *Dosage varies depending on condition type/severity, dosing interval, individual characteristics ANTACIDS Figure 1.9 Antacids: mechanism of action. 6 OSMOSIS.ORG

Gastrointestinal Acid Reducing Medications WHAT ARE THEY? Mechanism of action ▪ Weak bases bind to H+ → neutralize gastric pH Key points ▪ Less effective than PPIs / H2 antagonists ▪ Calcium carbonate/sodium bicarbonate absorbed in GI tract → systemic side effects; less popular antacids TYPES ▪ Aluminum hydroxide (Amphojel): PO ▪ Magnesium hydroxide (milk of magnesia): PO ▪ Aluminum hydroxide + magnesium hydroxide (Gelusil): PO ▪ Calcium carbonate (Tums): PO ▪ Sodium bicarbonate: PO CLINICAL CONCERNS ADVERSE EFFECTS ▪ Drug-specific adverse effects ▪ Aluminum hydroxide: constipation ▪ Magnesium hydroxide: diarrhea, hypotension (rare) ▪ Calcium carbonate/sodium bicarbonate: milk-alkali syndrome (metabolic alkalosis, hypercalcemia, renal insufficiency) DISEASE-RELATED CONCERNS ▪ Renal impairment: dosage reduction ▫ Aluminum hydroxide: hypophosphatemia, proximal muscle weakness, osteoporosis, seizures ▫ Magnesium hydroxide: hypermagnesemia, hyporeflexia, cardiac arrest Common indications ▪ Symptomatic relief in GERD Figure 1.10 Antacids: general adult dosing guidelines. *Dosage varies depending on condition type/severity, dosing interval, individual characteristics OSMOSIS.ORG 7

Figure 1.11 Antacids: common drug-drug interactions. 8 OSMOSIS.ORG