Famotidine (Pepcid) Dosing for Acid Reduction
For acid reduction in peptic ulcer disease and GERD, famotidine 20 mg twice daily or 40 mg at bedtime are the standard recommended dosages, with both regimens demonstrating equivalent efficacy. 1
Standard Dosing Regimens
Active Peptic Ulcer Disease
- Duodenal ulcer: 40 mg once daily at bedtime OR 20 mg twice daily 1, 2
- Gastric ulcer: 40 mg once daily at bedtime 1
- Both regimens achieve similar healing rates to cimetidine 800 mg daily or ranitidine 300 mg daily 2, 3
Gastroesophageal Reflux Disease (GERD)
- Symptomatic GERD: 20 mg twice daily provides superior symptom relief compared to 40 mg at bedtime 1
- Erosive esophagitis: 40 mg twice daily demonstrates significantly greater healing rates at 6 and 12 weeks compared to 20 mg twice daily or placebo 1
- The 40 mg twice daily regimen healed 48% of erosive esophagitis at 6 weeks versus 32% with 20 mg twice daily and 18% with placebo 1
Maintenance Therapy
- Duodenal ulcer recurrence prevention: 20 mg once daily at bedtime reduces 12-month recurrence rates to 23% versus 57% with placebo 1, 4
- The 20 mg bedtime dose is the recommended maintenance regimen 4
Pharmacodynamic Considerations
Duration of Action
- Single bedtime dose (40 mg): Provides antisecretory activity for approximately 10-12 hours, primarily covering nocturnal and morning periods 5, 6
- Maintains intragastric pH above 4 for nearly 50% of a 24-hour period 5
- Intramuscular administration (20 mg): Provides acid suppression for approximately 6 hours 6, 7
Potency
- Famotidine is 20-50 times more potent than cimetidine and 7.5-8 times more potent than ranitidine on a weight basis 2, 3
Alternative Routes of Administration
Intramuscular Dosing
- 20 mg IM is effective for perioperative acid reduction when oral or IV routes are unavailable 6, 7
- Provides approximately 6 hours of acid suppression 6
- Recognized by the American Society of Anesthesiologists as effective for reducing gastric volume and acidity 7
Pathological Hypersecretory Conditions
- Zollinger-Ellison syndrome: Dosages range from 20 mg to 160 mg every 6 hours, individualized to maintain basal acid secretion below 10 mEq/hour 1
- Initial dosing requires titration and subsequent adjustments over time 1
Critical Clinical Considerations
Tachyphylaxis
- Tolerance develops within 6 weeks of continuous H2-receptor antagonist therapy 6, 7
- Requires periodic reassessment of continued need for therapy 6
Drug Interactions
- Famotidine does not interfere with clopidogrel's antiplatelet activity, making it the preferred acid suppressor over PPIs in patients on dual antiplatelet therapy 8, 6, 9
- The American Heart Association specifically recommends H2 antagonists as alternatives to PPIs in this population 8
- No significant drug interactions with hepatic metabolism, unlike cimetidine 2, 3