What is the dosage and administration of liquid famotidine (histamine-2 (H2) receptor antagonist) for patients with impaired renal function or difficulty swallowing?

Liquid Famotidine Dosing and Administration

Liquid famotidine (oral suspension) is available at a concentration of 6 mg/mL and should be dosed according to indication, patient weight, and renal function, with dose reductions required for creatinine clearance below 60 mL/min. 1

Standard Dosing for Patients with Normal Renal Function

Adults and Pediatric Patients ≥40 kg

• Active duodenal ulcer: 40 mg once daily OR 20 mg twice daily for up to 8 weeks 1
• Active gastric ulcer: 40 mg once daily for up to 8 weeks 1
• Symptomatic non-erosive GERD: 20 mg twice daily for up to 6 weeks 1
• Erosive esophagitis: 20 mg twice daily OR 40 mg twice daily for up to 12 weeks 1

Pediatric Patients <40 kg

• The 20 mg and 40 mg tablet formulations are not recommended for patients weighing less than 40 kg; use the oral suspension formulation instead 1
• Specific weight-based dosing should be calculated using the 6 mg/mL suspension concentration 1

Dosing for Patients with Renal Impairment

Famotidine is 70% eliminated unchanged through the kidneys, primarily via both glomerular filtration and tubular secretion, making dose adjustment essential in renal dysfunction. 2, 3

Creatinine Clearance 30-60 mL/min (Moderate Impairment)

• Active duodenal ulcer: 20 mg once daily OR 40 mg every other day 1
• Active gastric ulcer: 20 mg once daily OR 40 mg every other day 1
• Symptomatic non-erosive GERD: 20 mg once daily 1
• Erosive esophagitis: 20 mg once daily OR 40 mg every other day 1

Creatinine Clearance <30 mL/min (Severe Impairment)

• All indications: 20 mg every other day (alternate dosing: 10 mg once daily, which requires using the oral suspension since tablets cannot be split) 1
• For ulcer recurrence prevention: 10 mg every other day using oral suspension 1

Pharmacokinetic Rationale

• Elimination half-life increases from 2.6-3.6 hours in normal renal function to 4.72 hours in moderate renal failure and 12.07 hours in severe renal failure 3
• Renal clearance of famotidine (310 mL/min) exceeds creatinine clearance (109 mL/min) in healthy adults, confirming active tubular secretion 4
• The ratio of famotidine renal clearance to creatinine clearance decreases as kidney function worsens, indicating that tubular secretion deteriorates faster than glomerular filtration 4

Administration Instructions for Liquid Formulation

Preparation and Storage

• Oral suspension is reconstituted to provide a final concentration of 6 mg/mL 1
• If commercially manufactured suspension is unavailable, pharmacies can compound a suspension from tablets (final concentration: 15 mg/mL) 1

Dosing Volumes for 6 mg/mL Suspension

• 30 mg dose: 5 mL of oral suspension 1
• 45 mg dose: 7.5 mL of oral suspension 1
• 60 mg dose: 10 mL of oral suspension 1
• 75 mg dose: 12.5 mL of oral suspension 1

Timing and Food Interactions

• Take once daily before bedtime OR twice daily in the morning and before bedtime, as recommended 1
• May be taken with or without food, though administration with meals may improve gastrointestinal tolerability 1
• May be given with antacids 1

Special Considerations for Swallowing Difficulties

• The liquid formulation is ideal for patients with dysphagia or difficulty swallowing tablets 1
• Antisecretory activity begins within 1 hour after oral administration, reaches maximum effect in 1-3 hours, and lasts 10-12 hours 5
• Peak plasma concentrations are attained within 2-4 hours with oral bioavailability of 40-50% 2

Important Clinical Caveats

Antacid Interactions

• Coadministration of potent antacids reduces oral absorption of famotidine by 20-30%, though famotidine may still be given with antacids 2

Dialysis Patients

• Blood purification procedures (hemodialysis, peritoneal dialysis, hemofiltration) do not remove famotidine to a clinically significant degree 2, 6
• Dose adjustment based on residual renal function is still required 6

Elderly Patients

• Plasma elimination and renal excretion are decreased in elderly patients, though dose adjustment is not required for mild renal insufficiency 4
• Monitor for accumulation during long-term therapy in elderly patients with declining renal function 4

Pathological Hypersecretory Conditions

• Starting dosage: 20 mg every 6 hours, adjusted to individual patient needs up to maximum 160 mg every 6 hours 1
• Avoid use in patients with creatinine clearance <30 mL/min as required doses may exceed maximum doses evaluated in renally-impaired patients 1