RANITIDINE HYDROCHLORIDE
Clinical safety rating: safe
No significant drug interactions May cause confusion more commonly in elderly or severely ill patients.
Competitive, reversible inhibitor of histamine H2 receptors on gastric parietal cells, reducing gastric acid secretion (both basal and stimulated).
| Metabolism | Primarily metabolized via N-oxide formation, S-oxidation, and N-demethylation; involves CYP450 isoenzymes (CYP1A2, CYP2C19, CYP2D6, and CYP3A4). |
| Excretion | Renal (70%) via tubular secretion and glomerular filtration; minimal biliary/fecal (<5% unchanged). |
| Half-life | Terminal elimination half-life: 2.5–3.5 hours (prolonged in renal impairment). |
| Protein binding | 15% bound primarily to albumin. |
| Volume of Distribution | Vd: 1.2–1.9 L/kg (extensive tissue distribution). |
| Bioavailability | Oral: 50% (extensive first-pass metabolism); IM: 90–100%. |
| Onset of Action | Oral: 60 minutes; IM: 45 minutes; IV: 15 minutes. |
| Duration of Action | Oral: 6–8 hours; IM/IV: 6–12 hours (dose-dependent). |
150 mg orally twice daily or 300 mg orally once daily at bedtime; alternatively, 50 mg intramuscularly or intravenously every 6-8 hours.
| Dosage form | SYRUP |
| Renal impairment | GFR 30-50 mL/min: reduce dose to 150 mg orally once daily. GFR 15-29 mL/min: 150 mg orally every 18-24 hours. GFR <15 mL/min: 150 mg orally every 24 hours or 50 mg intravenously every 18-24 hours. |
| Liver impairment | Child-Pugh Class B or C: reduce dose by 50% or prolong dosing interval to every 12-24 hours orally; no specific IV adjustment guidelines; use with caution. |
| Pediatric use | 1 month to <12 years: 2-4 mg/kg orally twice daily, max 300 mg/day; 12-18 years: 2-4 mg/kg orally twice daily, max 300 mg/day; IV: 1-2 mg/kg every 6-8 hours, max 50 mg/dose. |
| Geriatric use | Reduce dose by 50% (e.g., 150 mg once daily) due to age-related renal impairment; monitor for CNS adverse effects; maximum daily dose 300 mg. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
No significant drug interactions May cause confusion more commonly in elderly or severely ill patients.
| FDA category | Animal |
| Breastfeeding | Excreted in human milk; M/P ratio approximately 1.9 (range 1.4-4.8). Peak milk concentration occurs 2-3 hours after dose. Infant dose is about 2-7% of maternal weight-adjusted dose. Not expected to cause adverse effects in infants with maternal doses up to 300 mg/day. Consider timing breastfeeding after drug administration to reduce exposure. |
| Teratogenic Risk |
■ FDA Black Box Warning
No FDA black box warning.
| Common Effects | GERD |
| Serious Effects |
["Hypersensitivity to ranitidine or any component of the formulation","Acute porphyria (including porphyria cutanea tarda, symptomatic porphyria, and variegate porphyria)"]
| Precautions | ["Potential to mask symptoms of gastric malignancy","May cause vitamin B12 deficiency with prolonged use (especially in elderly, vegetarians, or malabsorption)","Risk of acute intermittent porphyria in susceptible patients","Risk of hepatotoxicity (rare, but discontinue if elevated liver enzymes)","Renal impairment: dose adjustment required (creatinine clearance <50 mL/min)","May interfere with urine protein tests (false-positive)","May increase risk of community-acquired pneumonia (limited evidence)"] |
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| FDA Pregnancy Category B. No evidence of teratogenicity in animal studies. Limited human data in first trimester suggest no increased risk of major malformations. In second and third trimesters, no known fetal risks. Crosses placenta but fetal concentrations are lower than maternal. Use only if clearly needed. |
| Fetal Monitoring | No specific monitoring required. Routine pregnancy monitoring. Monitor for maternal adverse effects such as headache, dizziness, gastrointestinal disturbances. In neonates, no specific monitoring indicated unless maternal toxicity or high doses used. |
| Fertility Effects | No known effects on fertility in humans. Animal studies showed no impairment of fertility at doses up to 160 mg/kg/day. No adverse effects on spermatogenesis or ovulation reported. |