ZANTAC 150
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZANTAC 150 (ZANTAC 150).
Competitive histamine H2-receptor antagonist that inhibits basal and stimulated gastric acid secretion by blocking H2 receptors on parietal cells in the stomach.
| Metabolism | Metabolized by the liver (ca. 30% of dose) via N-oxidation, N-desmethylation, and S-oxidation; metabolism primarily involves CYP450 isoenzymes (CYP1A2, CYP2D6, and CYP3A4). |
| Excretion | Renal (70% unchanged via tubular secretion), biliary (30% as metabolites and unchanged drug). |
| Half-life | 2.5 hours (range 1.5-3.5 h); prolonged in renal impairment (creatinine clearance <50 mL/min: 4-8 h). |
| Protein binding | 15% bound to albumin. |
| Volume of Distribution | 1.2 L/kg (0.8-1.8 L/kg); distributes into total body water and breast milk. |
| Bioavailability | Oral: 50-60% (first-pass metabolism); IM: 90-100%. |
| Onset of Action | Oral: 30-60 minutes; IM: 15-30 minutes; IV: 5-10 minutes. |
| Duration of Action | 4-10 hours; single dose suppresses gastric acid for 8-12 h, tolerance may develop with repeated dosing. |
| Molecular Weight | 350.87 |
150 mg orally twice daily or 300 mg orally once daily at bedtime.
| Dosage form | CAPSULE |
| Renal impairment | CrCl 15-50 mL/min: 150 mg orally every 24 hours; CrCl <15 mL/min: 150 mg orally every 48 hours. |
| Liver impairment | No dose adjustment recommended for mild to moderate hepatic impairment; use caution in severe impairment with maximum dose of 150 mg daily. |
| Pediatric use | 1 month to 16 years: 2-4 mg/kg orally twice daily; maximum 300 mg/day. |
| Geriatric use | Reduce dose to 150 mg orally once daily due to age-related renal decline; consider renal function. |
| 1st trimester | Ranitidine crosses the placenta. Limited human data; animal studies show no teratogenicity at therapeutic doses. Use only if clearly needed. |
| 2nd trimester | No increased risk of major malformations reported. Considered relatively safe; use if clinically indicated. |
| 3rd trimester | No known adverse fetal effects. May be used for GERD or aspiration prophylaxis. |
Clinical note
Comprehensive clinical and safety monograph for ZANTAC 150 (ZANTAC 150).
| Placental transfer | Crosses placenta; fetal plasma concentrations approximately 50-70% of maternal levels. |
| Breastfeeding | Ranitidine is excreted into breast milk in low concentrations (milk:plasma ratio ~1.9). Typical infant dose is <10% of maternal weight-adjusted dose. No reported adverse effects in breastfed infants. Use with caution in premature infants or those with renal impairment. |
■ FDA Black Box Warning
No FDA boxed warning exists for Zantac (ranitidine). However, the FDA has issued a safety communication regarding the presence of a probable human carcinogen (NDMA) in ranitidine products and requested their removal from the market.
| Serious Effects |
Hypersensitivity to ranitidine or any componentAcute porphyria
| Precautions | May cause acute porphyria; contraindicated in patients with history of acute porphyria, May cause reversible confusional states, especially in elderly or severely ill patients, May cause hepatotoxicity (hepatitis, jaundice), May cause blood dyscrasias (leukopenia, agranulocytosis, thrombocytopenia), May cause interstitial nephritis, May cause hypersensitivity reactions (including anaphylaxis, angioedema, bronchospasm), Contains NDMA (N-nitrosodimethylamine), a probable human carcinogen; products recalled in many markets |
| Food/Dietary | Avoid excessive consumption of caffeine, alcohol, and spicy or acidic foods as they may exacerbate symptoms. No direct food-drug interactions but high-fat meals may delay absorption; take consistently with or without food. |
Loading safety data…
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | Pregnancy Category B. No evidence of teratogenicity in animal studies. Limited human data; first trimester exposure not associated with increased risk of major malformations. Second and third trimester: no known fetal risks at standard doses. |
| Fetal Monitoring | No specific monitoring required beyond routine prenatal care. Monitor for maternal adverse effects (headache, dizziness) and infant irritability or sedation if prolonged use. |
| Fertility Effects | No adverse effects on fertility reported in animal studies or human data. Ranitidine does not alter reproductive function. |
| Clinical Pearls | Zantac 150 (ranitidine) is a histamine-2 receptor antagonist (H2RA). Note that ranitidine was withdrawn from the US market in 2020 due to NDMA impurities; use famotidine as alternative. For IV use, administer over 5-15 minutes to avoid hypotension. In renal impairment (CrCl <50 mL/min), reduce dose to 150 mg daily. May interfere with CYP450 metabolism; monitor warfarin, theophylline, and phenytoin levels. Not effective for stress ulcer prophylaxis in ICU; use PPIs instead. |
| Patient Advice | Take without regard to meals; best if taken at bedtime for duodenal ulcer maintenance. · Do not take with antacids within 1 hour of administration. · Avoid alcohol and smoking to maximize efficacy. · Report any muscle pain, confusion, or bradycardia to your doctor. · If pregnant or breastfeeding, consult healthcare provider before use. |