What is the recommended IV dose of famotidine (H2 receptor antagonist) for adults with impaired renal function?

Famotidine IV Dosing in Adults with Renal Impairment

For adults with moderate to severe renal impairment (creatinine clearance <50 mL/min), reduce the famotidine IV dose to 20 mg every 24 hours or extend the dosing interval to 36-48 hours, rather than the standard 20 mg every 12 hours used in patients with normal renal function. 1

Standard Dosing in Normal Renal Function

• The recommended IV dose for adults with normal renal function is 20 mg every 12 hours 1
• This can be administered as a slow IV push over at least 2 minutes or as a 15-30 minute infusion 1
• For stress ulcer prophylaxis specifically, guidelines support 20 mg IV twice daily or 40 mg once daily 2

Renal Dose Adjustment Algorithm

When creatinine clearance is <50 mL/min:

• Reduce the dose to half (10 mg every 12 hours), OR
• Extend the dosing interval to 36-48 hours while maintaining the 20 mg dose 1

Rationale: Famotidine is eliminated primarily through the kidneys (approximately 70% as unchanged drug), and the elimination half-life increases dramatically in renal insufficiency 3. In severe renal impairment (CrCl <10 mL/min), the half-life can exceed 20 hours and reach approximately 24 hours in anuric patients 1

Critical Safety Considerations

• CNS adverse effects have been specifically reported in patients with moderate and severe renal insufficiency, making dose reduction essential to avoid drug accumulation 1
• The prolonged half-life in renal impairment (compared to 2.8 hours in normal function) necessitates these adjustments to prevent toxicity 3

Practical Administration

• IV push preparation: Dilute 2 mL of famotidine injection (10 mg/mL) with 0.9% sodium chloride to 5-10 mL total volume and inject over at least 2 minutes 1
• IV infusion preparation: Dilute 2 mL in 100 mL of compatible solution and infuse over 15-30 minutes 1
• Antacids may be given concomitantly if needed 1

Common Pitfalls to Avoid

• Do not use standard every-12-hour dosing in patients with CrCl <50 mL/min without dose adjustment, as this significantly increases the risk of CNS toxicity due to drug accumulation 1
• Monitor elderly patients particularly closely, as they often have age-related decline in renal function that may not be reflected in serum creatinine alone 3
• When extending dosing intervals, the preferred approach is to maintain the 20 mg dose rather than giving smaller, more frequent doses, as this takes advantage of famotidine's dose-dependent antisecretory effect 1