H2 Receptor Antagonist Therapy for Reducing Stomach Acid Production

Potency and Efficacy Differences

• Famotidine is 20-50 times more potent than cimetidine, while ranitidine is only 7 times more potent than cimetidine 1

Clinical Equivalence in Standard Dosing

• Both agents are effective for reducing gastric volume and acidity in the perioperative period 2, 3, 4
• For NSAID-related ulcer prevention, standard doses of H2 receptor antagonists reduce duodenal but not gastric ulcers 5, 6

Safety and Tolerability

• Both agents are very well tolerated with rare side effects 1
• Both H2 receptor antagonists can develop tachyphylaxis within 6 weeks of treatment initiation, limiting their effectiveness for long-term use 1, 7

Drug Interaction Considerations

• Famotidine does not interfere with clopidogrel's antiplatelet activity, making it preferable to PPIs in patients on dual antiplatelet therapy 8, 7
• The American College of Cardiology recommends famotidine over PPIs for patients on dual antiplatelet therapy 8, 7

Clinical Algorithm for Selection

• Consider PPIs instead of H2 receptor antagonists when long-term therapy is needed to avoid tachyphylaxis 1, 7
• Consider PPIs instead of H2 receptor antagonists when patient is H. pylori-positive with NSAID use 5, 6

Pediatric Considerations

• Ranitidine is FDA-approved for children 1 month to 16 years at 5-10 mg/kg/day divided in 2-3 doses 1
• Side effects are very rare in children with both agents 1

Famotidine and Ranitidine Comparison

Introduction to Famotidine and Ranitidine

• Famotidine is a more potent H2 receptor antagonist compared to ranitidine, with a potency 8-9 times stronger and a longer duration of action, and does not interact with the cytochrome P-450 system, making it safer for patients using clopidogrel or other medications metabolized through this pathway 9

Perbedaan Potensi and Efikasi

• Kedua obat sama-sama efektif untuk dosis standar dalam mencegah ulkus duodenum terkait NSAID, namun tidak efektif untuk ulkus gaster pada dosis standar 10, 11

Perbedaan Metabolisme and Interaksi Obat

• Famotidine tidak berinteraksi dengan sistem sitokrom P-450, sehingga tidak mempengaruhi metabolisme obat lain 9
• Ranitidine berinteraksi lemah dengan sitokrom P-450, sementara famotidine sama sekali tidak mengikat sistem ini 9

Pertimbangan Klinis untuk Pemilihan

• Untuk pasien dengan risiko perdarahan GI yang tinggi pada terapi antiplatelet, famotidine lebih disukai dibandingkan ranitidine karena profil interaksi obat yang lebih baik 9, 12
• Antagonis H2 dosis standar hanya efektif mencegah ulkus duodenum, bukan ulkus gaster terkait NSAID; diperlukan dosis ganda untuk proteksi ulkus gaster 10, 11