ZANTAC 300
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZANTAC 300 (ZANTAC 300).
Competitive antagonist of histamine at H2 receptors on gastric parietal cells, reducing basal and stimulated gastric acid secretion.
| Metabolism | Hepatic metabolism via N-oxidation, S-oxidation, and N-demethylation; minor renal excretion of unchanged drug. |
| Excretion | Renal (approximately 30% unchanged active drug via tubular secretion and glomerular filtration); hepatic metabolism to N-oxide, S-oxide, and desmethyl metabolites (about 70% of dose); fecal excretion (minor, <5%). |
| Half-life | Approximately 2.5–3 hours in patients with normal renal function; prolonged in renal impairment (creatinine clearance <30 mL/min: up to 6–12 hours). |
| Protein binding | Approximately 15% bound to plasma proteins (mainly albumin). |
| Volume of Distribution | 1.2–1.8 L/kg; extensive extravascular distribution indicates good tissue penetration. |
| Bioavailability | Oral: 50–60% (first-pass metabolism); IM: 90–100%. |
| Onset of Action | Oral: 30–60 minutes; intravenous: 15–30 minutes; intramuscular: 20–30 minutes. |
| Duration of Action | Oral: 8–12 hours (single dose); intravenous: 6–8 hours; prolonged with multiple dosing due to drug accumulation. |
300 mg orally once daily at bedtime or 150 mg orally twice daily.
| Dosage form | CAPSULE |
| Renal impairment | For CrCl 15-50 mL/min: 150 mg orally once daily. For CrCl <15 mL/min: 150 mg orally every 24 hours or 75 mg orally every 12 hours. Hemodialysis: Administer dose after dialysis. |
| Liver impairment | For Child-Pugh class A or B: No adjustment necessary. For Child-Pugh class C: Consider dose reduction to 150 mg daily; monitor for adverse effects. |
| Pediatric use | For infants >1 month and children: 2-4 mg/kg orally twice daily; maximum 300 mg/day. For neonates (<1 month): 2 mg/kg orally every 12-24 hours. |
| Geriatric use | Consider age-related renal impairment; adjust dose based on CrCl. In elderly with normal renal function, standard dosing may be used but monitor for confusion and side effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ZANTAC 300 (ZANTAC 300).
| Breastfeeding | Excreted in breast milk; M/P ratio approximately 1.0. Concentrations are low, estimated infant dose < 6% of maternal weight-adjusted dose. Generally considered compatible with breastfeeding; use lowest effective dose. |
| Teratogenic Risk | Pregnancy Category B. No evidence of teratogenicity in animal studies; inadequate human studies in first trimester. Crosses placenta but no increased risk of major malformations or adverse fetal outcomes reported. Use only if clearly needed. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to ranitidine or any component","Acute porphyria (historical or current)"]
| Precautions | ["Potential for acute porphyria in susceptible patients","May increase gastric pH and predispose to enteric infections","Risk of vitamin B12 deficiency with chronic use","May cause confusion or delirium in elderly","Use with caution in renal impairment (reduce dose)","May increase serum creatinine falsely","Possible risk of community-acquired pneumonia"] |
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| No routine monitoring required. Monitor for maternal side effects (headache, dizziness, GI disturbances). In prolonged use, assess renal function and CBC if indicated. |
| Fertility Effects | No known adverse effects on fertility. Ranitidine does not impair spermatogenesis or oocyte maturation in animal or human studies. |