H2 Antagonists
H2 Antagonists: Drug Interactions
*cimetidine (Tagamet) - liver Acidic environment for absorption: all H2 antagonists may inhibit the absorption of drugs that require an acidic GI environment for absorption such as Nizoral (ketoconazole) Smoking increases HCl and decreases the effectiveness of H2 blockers
*cimetidine (Tagamet)
• Increased drug levels: binds with P-450 microsomal oxidase system in the liver, resulting in inhibited oxidation of many drugs • Inhibit the absorption of drugs that require an acidic GI environment
*H2 Antagonists: Adverse Effects
• Overall, very few adverse effects • Cimetidine may induce impotence and gynecomastia • May cause headaches, lethargy, confusion, diarrhea, urticaria, sweating, flushing, other effects
H2 Antagonists: Drug Examples
• cimetidine (Tagamet) • nizatidine (Axid) • *famotidine (Pepcid) • ranitidine (Zantac)
H2 Antagonists
Histamine Type 2 (H2) Antagonists • Reduce acid secretion • All available over the counter in lower dosage forms • Most popular drugs for treatment of acid-related disorders
H2 Antagonists: Effects
Suppressed acid secretion in the stomach
H2 Antagonists: Mechanism of Action
• Block histamine at the (H2) receptors of acid-producing parietal cells • Production of hydrogen ions is reduced -> decreased production of HCl
Which acid controlling drug can cause confusion and disorientation (especially for elderly patients)?
H2 Antagonist
H2 Antagonists: Indications
• GERD: gastroesophageal reflux disease • PUD: peptic ulcer disease • Erosive esophagitis • Adjunct therapy to control upper GI bleeding • Pathologic gastric hypersecretory conditions
H2 Antagonists: Nursing Implications
• *Assess for allergies and impaired renal or liver function • *Take 1 hour before or after antacids or rendered ineffective • Use with caution in patients: confused, disoriented, or elderly • Stay alert to mental status changes • IV doses: monitor for hypotension, cardiac arythmias • Monitor look for blood; black stool or hematemesis (vomiting blood), indicating that condition is not being resolved
