Pepcid (Famotidine) Intramuscular Dosing
Famotidine can be administered intramuscularly, though this route is rarely used in clinical practice; when IM administration is necessary, the dose is typically 20 mg, which provides effective gastric acid suppression comparable to oral dosing. 1
Evidence for IM Famotidine
The American Society of Anesthesiologists guidelines specifically acknowledge that intramuscular famotidine is effective in reducing gastric volume and acidity during the perioperative period based on placebo-controlled randomized controlled trial evidence. 1 This represents Category A3-B evidence, indicating moderate-quality data supporting its efficacy.
Dosing Considerations
Standard IM Dose
- 20 mg intramuscularly is the established dose based on clinical trial data 1
- This dose provides acid suppression lasting approximately 6 hours 2
- Onset of antisecretory activity begins within 1 hour of administration 3
Comparative Potency
- Intravenous famotidine is approximately twice as potent as oral administration, consistent with oral bioavailability of about 43% 3
- IM administration would be expected to have similar bioavailability to IV dosing, making it more potent than oral routes 3
- Famotidine is 20-50 times more potent than cimetidine and 8 times more potent than ranitidine on a weight basis 4
Clinical Context and Alternatives
When to Consider IM Route
- Perioperative settings where oral administration is not feasible due to NPO status 1
- Patients unable to take oral or IV medications
- Critical care settings where stress ulcer prophylaxis is needed, though IV or enteral routes are preferred 1
Preferred Routes in Practice
- Oral and IV routes are more commonly used than IM administration 1
- For stress ulcer prophylaxis in critically ill adults, low-dose famotidine (≤40 mg daily) is recommended regardless of route 1
- The enteral route is generally preferred when the GI tract is functional 1
Important Caveats
Renal Adjustment
- Famotidine is eliminated primarily through the kidneys (approximately 70%) 3
- Elimination half-life is prolonged nonlinearly in patients with decreased renal function, requiring dose adjustment 3
Duration Limitations
- Tachyphylaxis can develop within 6 weeks of initiating H2 receptor antagonist therapy 5, 2
- Periodic assessment of continued need for therapy is recommended for long-term use 5