Ranitidine 50 mg IV Dosing
For adults, administer ranitidine 50 mg intravenously every 6 to 8 hours, either as an intermittent bolus (diluted to ≤2.5 mg/mL and injected over 5 minutes) or as an intermittent infusion (diluted to ≤0.5 mg/mL and infused over 15-20 minutes). 1
Standard Adult Dosing
The FDA-approved dose is 50 mg (2 mL) every 6 to 8 hours for hospitalized patients with pathological hypersecretory conditions, intractable duodenal ulcers, or those unable to take oral medication. 1
For intermittent bolus administration: Dilute 50 mg in 0.9% sodium chloride or compatible IV solution to a concentration no greater than 2.5 mg/mL (20 mL total volume) and inject at a rate no greater than 4 mL/min (5 minutes). 1
For intermittent infusion: Dilute 50 mg in 5% dextrose or compatible IV solution to a concentration no greater than 0.5 mg/mL (100 mL total volume) and infuse over 15-20 minutes. 1
Maximum daily dose should generally not exceed 400 mg/day, though dosage increases may be necessary in some patients by administering doses more frequently. 1
Pediatric Dosing
The recommended total daily dose in pediatric patients is 2 to 4 mg/kg/day, divided and administered every 6 to 8 hours, up to a maximum of 50 mg per dose. 1
For neonates less than 1 month of age (particularly those on ECMO): A dose of 2 mg/kg every 12 to 24 hours or as continuous infusion is usually sufficient to maintain gastric pH >4 for at least 15 hours. 1
Special Clinical Contexts
Angioedema Associated with Alteplase
Administer ranitidine 50 mg IV (or famotidine 20 mg IV as alternative) as part of the management protocol for orolingual angioedema associated with IV alteplase administration for acute ischemic stroke. 2
This should be given alongside IV methylprednisolone 125 mg and IV diphenhydramine 50 mg, after discontinuing alteplase infusion. 2
The Canadian Stroke Best Practice guidelines similarly recommend ranitidine 50 mg IV for tPA-induced angioedema management. 2
Anaphylaxis Management
Ranitidine 50 mg IV (diluted in 5% dextrose over 5 minutes) can be used as adjunctive therapy in adults with anaphylaxis. 3
For children with anaphylaxis: Use 12.5-50 mg (1 mg/kg) IV over 5 minutes as adjunctive therapy. 3
Critical caveat: H2 antagonists like ranitidine are second-line therapy to epinephrine and should never be administered alone in anaphylaxis. 4
The combination of diphenhydramine and ranitidine is superior to diphenhydramine alone for managing anaphylaxis. 4
Continuous Infusion Dosing
For continuous IV infusion: Add ranitidine to 5% dextrose or compatible solution and deliver at a rate of 6.25 mg/hour (e.g., 150 mg in 250 mL at 10.7 mL/hour). 1
For Zollinger-Ellison patients: Start infusion at 1.0 mg/kg/hour (concentration ≤2.5 mg/mL), adjusting upward in 0.5 mg/kg/hour increments if gastric acid output remains >10 mEq/hour or patient becomes symptomatic. Dosages up to 2.5 mg/kg/hour have been used. 1
Research demonstrates that continuous infusion regimens provide more constant acid suppression than bolus dosing, with an EC50 of approximately 45 ng/mL. 5
Renal Impairment Dosing
For creatinine clearance <50 mL/min: Reduce dose to 50 mg every 18 to 24 hours. 1
The frequency may be increased to every 12 hours if clinically required, with caution. 1
Hemodialysis consideration: Time the scheduled dose to coincide with the end of hemodialysis, as dialysis reduces circulating ranitidine levels. 1
Important Clinical Considerations
Onset of action: Gastric pH ≥4 is achieved 35-50 minutes after administration starts. 5
Stability: Ranitidine injection is stable for 48 hours at room temperature when diluted with commonly used IV solutions (0.9% sodium chloride, 5% dextrose, lactated Ringer's, 5% sodium bicarbonate). 1
The solution may exhibit yellow color that intensifies over time without affecting potency. 1
Pharmacokinetics: Elimination half-life is approximately 1.9 hours, with 50-70% of the dose excreted renally as unchanged drug. 6