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. |
| Molecular Weight | 350.87 |
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 | Limited human data; animal studies show no teratogenicity. Generally considered safe, but use only if clearly needed. |
| 2nd trimester | No evidence of fetal harm in human studies. Commonly used. |
| 3rd trimester | No known risk; may be used in pregnancy. |
Clinical note
Comprehensive clinical and safety monograph for ZANTAC 300 (ZANTAC 300).
| Placental transfer | Crosses the placenta; fetal serum concentrations are similar to maternal levels. |
| Breastfeeding | Ranitidine is excreted into breast milk in small amounts; concentrations are lower than therapeutic infant doses. Adverse effects in infants are unlikely. Consider monitoring for potential irritability or GI effects. |
| Lactation Rating |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to ranitidine or any componentAcute porphyria
| 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 |
| Food/Dietary | No significant food interactions; can be taken with or without food., Avoid excessive caffeine (coffee, tea, cola) as it may increase stomach acid., Avoid spicy, fatty, or acidic foods that can aggravate GERD or ulcer symptoms., Do not take with high-fat meals as they may delay absorption slightly; but clinical effect is not affected., Avoid alcohol as it can irritate the stomach lining and increase acid production. |
Loading safety data…
| L2 (Safer; limited data, but probably safe) |
| 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 | 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. |
| Clinical Pearls | Zantac 300 (ranitidine 300 mg) is a histamine H2-receptor antagonist used for duodenal ulcer, gastric ulcer, GERD, and Zollinger-Ellison syndrome. It is typically dosed once daily at bedtime for ulcer healing or twice daily for GERD. Renal dose adjustment is required (CrCl <50 mL/min: reduce dose to 150 mg daily). It may interfere with vitamin B12 absorption with long-term use. Ranitidine was withdrawn from the US market due to NDMA impurities; use famotidine as alternative. |
| Patient Advice | Take this medication exactly as prescribed, usually once daily at bedtime for ulcers or twice daily for GERD. · Avoid smoking and alcohol as they can worsen stomach acid problems and reduce drug effectiveness. · This drug may cause drowsiness or dizziness; avoid driving or operating machinery if affected. · Do not use over-the-counter antacids within 1 hour of taking ranitidine unless directed by your doctor. · Long-term use may increase risk of vitamin B12 deficiency; report symptoms like fatigue, weakness, or tingling. · If you miss a dose, take it as soon as you remember unless it is almost time for the next dose; do not double dose. · Keep out of reach of children and store at room temperature away from moisture and heat. |