Ranitidine

Gastroesophageal Reflux Disease

150 mg PO q12hr or 50 mg IM/IV q6-8hr

Gastric Ulcer, Benign

Treatment: 150 mg PO q12hr or 300 mg PO at bedtime

Maintenance of healing: 150 mg PO at bedtime

Erosive Esophagitis

Treatment: 150 mg PO q6hr or 50 mg IM/IV q6-8hr intermitent bolus or infusion; alternatively, 6.25 mg/hr IV by continuous infusion

Maintenance of healing: 150 mg PO q12hr

Hypersecretory Conditions

150 mg PO q12hr; up to 6 g/day used

Parenteral: 50 mg (2 mL) IM or intermitent IV bolus or infusion q6-8hr; not to exceed 400 mg/day; alternatively, 6.25 mg/hr continuous infusion

Dosing considerations

1. More frequent doses may be necessary; individualize dosage, and continue as long as indicated; dosages up to 6 g/day have been used for severe disease

2. Zollinger-Ellison syndrome: Start IV infusion at 1 mg/kg/hr, then adjust upward in 0.5 mg/kg/hr increments according to gastric acid output (not to exceed 2.5 mg/kg/hr or 220 mg/hr)

Stress Ulcer Prophylaxis (Off-label)

150 mg PO or NG q12hr

50 mg (2 mL) IM or intermitent IV bolus or infusion q6-8hr; not to exceed 400 mg/day; alternatively, 6.25 mg/hr continuous infusion

Dosing Modifications

Renal impairment (CrCl <50 mL/min): 50 mg IV/IM q18-24hr or 150 mg PO once daily

Hepatic impairment: Dosage adjustment not necessaryAdministrationMay be taken with or without food. OverdosageSeizures, ventricular arrhythmias, bradycardia, gait abnormalities, hypotension. Management: Should perform gastric lavage or induce emesis. Diazepam may be given for seizure, atropine for bradycardia and lidocaine for ventricular arrhythmias. Haemodialysis may enhance elimination.Contraindications

Hypersensitivity to ranitidine or components of the formulationSpecial Precautions

If gastroesophageal reflux disease does not respond adequately in 6-8 weeks, do not increase dosage; prescribe proton pump inhibitor instead

Prolonged treatment may lead to B12 malabsorption and subsequent vitamin B12 deficiency; degree of deficiency is dose-related and association stronger in females and younger in age (<30 years)

Use caution in renal impairment; adjust dosage

Use caution in hepatic impairment

Elevation of ALT levels reported with higher doses (≥100 mg) or prolonged IV therapy (≥5 days); monitor for ALT levels for the remainder of treatment

Avoid in patients with acute porphyria; may precipitate attack

Symptom relieve does not rule out presence of gastric malignancy

Reversible comfusional state reported with use (linked to age >50 years and renal or hepatic impairment); clears within 3-4 days after discontinuationAdverse Drug Reactions

1-10%

Headache (3%)

<1%

Abdominal pain, Agitation, Alopecia, Confusion, Constipation, Diarrhea, Dizziness, Hypersensitivity reaction, Nausea, Vomiting

Frequency Not Defined

Anemia, Necrotizing enterocolitis in fetus or newborn, Pancreatitis (rare), Thrombocytopenia (rare), Pancytopenia (rare), Agranulocytosis (rare), Acquired immune hemolytic anemia (rare), Arthralgia (rare), Myalgia (rare)

Potentially Fatal: Hepatotoxicity.Drug InteractionsDelayed absorption and increased peak serum concentration w/ propantheline bromide. Ranitidine minimally inhibits hepatic metabolism of coumarin anticoagulants, theophylline, diazepam and propanolol. May alter absorption of pH-dependent drugs (e.g. ketoconazole, midazolam, glipizide). May reduce bioavailability w/ antacids.Food InteractionMay cause gastric mucosal irritation with alcohol.Lab InterferenceFalse-positive results in urine protein determination using Multistix.Pregnancy Category (US FDA)Category BStorageIntravenous: Store between 4-25°C. Protect from light. Oral: Tab: Store between 15-30°C. Oral soln: Store between 4-25°C. Protect from light. Parenteral: Store between 4-25°C. Protect from light.Mechanism of ActionRanitidine competitively blocks histamine at H2-receptors of the gastric parietal cells which inhibits gastric acid secretion. It does not affect pepsin secretion, pentagastrin-stimulated intrinsic factor secretion or serum gastrin. Absorption: Readily absorbed from the GI tract. Bioavailability: Approx 50%. Time to peak plasma concentration: Approx 2-3 hr (oral); approx 15 min (IM). Distribution: Widely distributed; enters breast milk, crosses the placental barrier. Volume of distribution: Approx 1.4 L/kg. Plasma protein binding: Approx 15%. Metabolism: Hepatically metabolised. Small portion is converted to N-oxide (major metabolite, approx 4-6% of a dose), S-oxide and desmethylranitidine. Excretion: Via urine (oral: Approx 30%, IV: 70%) as unchanged drug and in the faeces. Elimination half-life: Approx 2-3 hr.