H2 Receptor Antagonists: Medication List
The four H2 receptor antagonists available for clinical use are cimetidine, ranitidine, famotidine, and nizatidine. 1, 2, 3, 2
Available H2 Receptor Antagonist Medications
1. Cimetidine
- An imidazole derivative that competitively inhibits histamine at H2 receptors of parietal cells 2
- Peak levels occur 45-90 minutes after oral administration with a half-life of approximately 2 hours 2
- Major limitation: Interacts with cytochrome P-450 hepatic enzyme system, affecting metabolism of other drugs 4, 5
- Associated with increased risk of liver disease and gynecomastia 1
- Least potent of the four H2RAs (famotidine is 40 times more potent on a weight basis) 4, 5
2. Ranitidine
- Belongs to the basically substituted furans structural class 4, 5
- Approximately 7 times more potent than cimetidine with longer duration of action 1
- Does not have the antiandrogenic activity seen with cimetidine 6
3. Famotidine
- Member of the guanidino-thiazole group 4, 5
- Most potent H2RA: approximately 8 times more potent than ranitidine and 40 times more potent than cimetidine 4, 5
- Does not interact with cytochrome P-450, avoiding drug-drug interactions 4, 5
- Preferred agent for patients on clopidogrel plus aspirin because it does not interfere with clopidogrel metabolism 1
- Longer duration of action than cimetidine or ranitidine 4, 5
4. Nizatidine
- Belongs to the basically substituted thiazoles structural class 3, 4
- Molecular formula C12H21N5O2S2 with molecular weight of 331.46 3
- Does not have antiandrogenic activity like cimetidine 6
Pharmacologic Properties Common to All H2RAs
- Suppress gastric acid production by 37% to 68% over 24 hours 6, 1
- Acid-inhibiting effects last approximately 6 hours 1
- Critical limitation: All develop tachyphylaxis within 6 weeks of treatment initiation, severely limiting long-term effectiveness 1
- Work better as prophylactic rather than acute treatment, as they must be present before histamine binds to receptors 1
- Generally well-tolerated with overall side-effect incidence of 2-3% 4, 5
Clinical Context
While all four medications are equally effective at usual recommended doses for mild GERD (>70% symptomatic improvement) 7, famotidine is the preferred choice in most clinical scenarios due to its superior potency, longer duration of action, lack of cytochrome P-450 interactions, and absence of antiandrogenic effects 1, 4, 5. The exception is when cost or availability dictates otherwise, as all four agents demonstrate similar efficacy for mild acid-related conditions 7.