What is the recommended dosing for ranitidine (histamine H2-receptor antagonist)?

Ranitidine Dosing Recommendations

The standard adult dose of ranitidine is 150 mg twice daily for most acid-related conditions, with pediatric dosing at 5-10 mg/kg/day divided into 2-3 doses (maximum 300 mg/day), though it is critical to note that ranitidine has been withdrawn from the US market due to NDMA contamination concerns. 1

Adult Dosing by Indication

Duodenal Ulcer

• Active disease: 150 mg twice daily OR 300 mg once daily at bedtime 1
• Maintenance: 150 mg at bedtime 1
• Higher doses (300 mg four times daily) provide superior healing rates compared to standard dosing, with 63% vs 29% complete healing at 4 weeks 2

Gastric Ulcer

• Active disease: 150 mg twice daily 1
• Maintenance: 150 mg at bedtime 1

GERD and Erosive Esophagitis

• GERD: 150 mg twice daily 1
• Erosive esophagitis (active): 150 mg four times daily 1
• Erosive esophagitis (maintenance): 150 mg twice daily 1

Pathological Hypersecretory Conditions

• Initial dose: 150 mg twice daily 1
• Dose adjustment: May require more frequent dosing; doses up to 6 g/day have been used in severe disease 1

Pediatric Dosing (Ages 1 Month to 16 Years)

Duodenal and Gastric Ulcers

• Active treatment: 2-4 mg/kg twice daily (maximum 300 mg/day) 1
• Maintenance: 2-4 mg/kg once daily (maximum 150 mg/day) 1

GERD and Erosive Esophagitis

• Recommended dose: 5-10 mg/kg/day divided into 2-3 doses (maximum 300 mg/day) 3, 1
• The American Academy of Pediatrics supports this weight-based dosing regimen 3

Over-the-Counter Dosing in Children

• Single dose: 75 mg for children aged 4-11 years provides effective acid suppression for 5-6 hours 4
• Peak plasma concentration occurs at 2.5 hours with a half-life of 2.0 hours 4

Special Population Dosing

Renal Impairment

• Creatinine clearance <50 mL/min: 150 mg every 24 hours 1
• May increase frequency to every 12 hours if clinically necessary 1
• Hemodialysis: Time dosing to coincide with end of dialysis session 1

Critically Ill Pediatric Patients (Stress Ulcer Prophylaxis)

• Recommended dose: 1.5 mg/kg IV every 6 hours maintains gastric pH ≥4 in 80% of patients 5
• Lower doses (0.75 mg/kg IV every 6 hours or oral regimens) are less effective 5

Anaphylaxis Management (Second-Line Therapy)

• Adult dose: 50 mg IM or IV 6, 7
• Pediatric dose: 1 mg/kg IM (maximum 50 mg) 3, 6, 7
• Must be used in combination with diphenhydramine and never as monotherapy 7
• Should only be administered after epinephrine, as H2 antagonists are second-line therapy 7

Important Clinical Considerations

Limitations of Ranitidine Therapy

• Tachyphylaxis: Develops within 6 weeks of continuous use 3
• Efficacy: Less effective than PPIs for healing erosive esophagitis 3
• Dosing frequency: Requires 2-3 times daily dosing due to 6-hour duration of acid suppression 3

Safety Profile

• Adverse events occur in 20% of ranitidine-treated patients vs 27% on placebo 8
• No dose-related toxicity across an eightfold range of therapeutic doses 8
• Generally well-tolerated with mild adverse events in pediatric populations 4

Critical Pitfall

Ranitidine was withdrawn from the US market in 2020 due to unacceptable levels of N-nitrosodimethylamine (NDMA), a probable human carcinogen. Alternative H2 receptor antagonists (famotidine) or PPIs should be used instead for current clinical practice.