What is the recommended dosage of ranitidine (H2 antagonist) for an adult patient with hypersensitivity reaction and potential gastrointestinal symptoms, considering renal or hepatic impairment?

Ranitidine Dosing for Adults

The standard adult dosage of ranitidine is 150 mg orally twice daily or 300 mg once daily at bedtime for most gastrointestinal conditions, with dose reduction to 150 mg every 24 hours required for patients with creatinine clearance <50 mL/min. 1

Standard Adult Dosing by Indication

Active Duodenal or Gastric Ulcer

• 150 mg orally twice daily is the primary recommended regimen 1
• Alternative: 300 mg once daily after the evening meal or at bedtime for patients requiring dosing convenience 1
• Antacids may be used as needed for breakthrough pain 1

Gastroesophageal Reflux Disease (GERD)

• 150 mg orally twice daily 1

Erosive Esophagitis (Active Treatment)

• 150 mg orally four times daily (higher frequency required for more severe disease) 1

Maintenance Therapy

• 150 mg once daily at bedtime for maintenance of healed duodenal ulcers, gastric ulcers, or erosive esophagitis 1

Pathological Hypersecretory Conditions (Zollinger-Ellison Syndrome)

• Start with 150 mg orally twice daily 1
• Adjust dosage based on individual patient response; some patients require more frequent 150 mg doses 1
• Dosages up to 6 g/day have been used in severe disease 1
• Continue treatment as long as clinically indicated 1

Critical Dose Adjustments for Renal Impairment

For patients with creatinine clearance <50 mL/min, reduce dosage to 150 mg every 24 hours. 1 This is a mandatory adjustment, not optional.

• If clinical condition requires more frequent dosing, may cautiously increase to every 12 hours 1
• Hemodialysis removes ranitidine; ideally time the scheduled dose to coincide with the end of hemodialysis 1
• Monitor closely for adverse effects as drug accumulation occurs with renal insufficiency 1

Elderly Patient Considerations

• Elderly patients are more likely to have decreased renal function 1
• Exercise caution in dose selection and monitor renal function 1
• If creatinine clearance is reduced, apply the renal dosing adjustments above 1
• No specific age-based dose reduction is required if renal function is normal 1

Pediatric Dosing (Ages 1 Month to 16 Years)

Active Duodenal and Gastric Ulcers

• 2 to 4 mg/kg orally twice daily, maximum 300 mg/day 1

Maintenance of Healed Ulcers

• 2 to 4 mg/kg orally once daily, maximum 150 mg/day 1

GERD and Erosive Esophagitis

• 5 to 10 mg/kg/day in 2 divided doses (based on published literature) 1

Note: Insufficient data exists for neonates <1 month of age; no dosing recommendations can be made 1

Important Clinical Context

The evidence provided focuses primarily on influenza antiviral medications (amantadine, rimantadine, zanamivir, oseltamivir) 2, which are not relevant to ranitidine dosing. One guideline mentions ranitidine briefly in the context of short bowel syndrome, recommending 300 mg orally twice daily or equivalent H2-antagonist dosing to reduce jejunostomy output 2.

Safety Considerations

• Ranitidine is generally well-tolerated with serious adverse effects being rare 3, 4, 5
• Anaphylaxis has been reported on very rare occasions; if hypersensitivity reaction occurs, discontinue immediately 6
• Unlike cimetidine, ranitidine lacks antiandrogenic effects and does not significantly alter hepatic drug metabolism 4, 5
• Ranitidine has been used safely in obstetric patients, children, elderly, and patients with renal impairment when dosed appropriately 3

Pharmacokinetic Properties Relevant to Dosing

• Oral bioavailability is approximately 88% 7
• Elimination half-life is approximately 1.9 hours 7
• 50-70% of the dose is renally excreted unchanged 7
• Peak plasma levels occur at approximately 1.6 hours after oral administration 7