FAMOTIDINE PRESERVATIVE FREE IN PLASTIC CONTAINER
Clinical safety rating: safe
No significant drug interactions May cause confusion more commonly in elderly or severely ill patients.
Competitive antagonist of histamine H2 receptors on gastric parietal cells, inhibiting basal and stimulated gastric acid secretion via inhibition of adenylate cyclase and reduced cAMP levels.
| Metabolism | Approximately 30-35% hepatic metabolism via cytochrome P450 enzymes (minor), primarily excreted unchanged in urine (65-70%) via tubular secretion and glomerular filtration. |
| Excretion | Renal: 65-70% unchanged; hepatic metabolism: 30-35%; minor biliary/fecal excretion |
| Half-life | 2.5-3.5 hours in normal renal function; prolonged to 20-24 hours in severe renal impairment (CrCl <10 mL/min) |
| Protein binding | 15-20% (primarily to albumin) |
| Volume of Distribution | 1.0-1.4 L/kg; distributes widely into tissues including CNS |
| Bioavailability | Oral: 40-50%; intramuscular: 90-100%; IV: 100% |
| Onset of Action | IV: within 30 minutes; oral: 1-3 hours |
| Duration of Action | 10-12 hours after single IV dose; up to 24 hours with multiple dosing; acid suppression persists for 12-24 hours |
20 mg intravenously every 12 hours; for hypersecretory conditions, 20 mg intravenously every 6 hours.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl <50 mL/min: 50% reduction in dose or increase dosing interval to every 36-48 hours; CrCl <10 mL/min: 75% reduction in dose or every 48-72 hours. |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B); severe impairment (Child-Pugh C): consider dose reduction due to potential accumulation, though specific guidelines not established. |
| Pediatric use | Neonates: 0.5 mg/kg/dose IV every 24 hours; Infants to adolescents: 0.5-1 mg/kg/dose IV every 8-12 hours (max 40 mg/day). |
| Geriatric use | Reduce dose based on renal function; monitor for confusion and CNS side effects; consider starting at lower end of dosing range. |
| 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 | Famotidine is excreted in human milk; M/P ratio is approximately 1.78. Infant exposure is low (estimated less than 10% of maternal weight-adjusted dose). Considered compatible with breastfeeding; monitor infant for potential gastrointestinal effects. |
| Teratogenic Risk | FDA Category B. No evidence of teratogenicity in animal studies. Limited human data; no increased risk of major birth defects observed. Risk in first trimester is low, but use only if clearly needed. Second and third trimester: no known fetal harm. |
■ FDA Black Box Warning
None.
| Common Effects | GERD |
| Serious Effects |
["Hypersensitivity to famotidine or other H2 receptor antagonists","Severe renal impairment (creatinine clearance <10 mL/min) if unable to adjust dose"]
| Precautions | ["Central nervous system (CNS) adverse reactions including confusion, delirium, hallucinations, and agitation, especially in elderly or renally impaired patients","Risk of Clostridioides difficile infection due to reduced gastric acidity","Potential for vitamin B12 deficiency with long-term use","Cross-sensitivity in patients with hypersensitivity to other H2 receptor antagonists","May mask symptoms of gastric malignancy","Renal impairment requires dose reduction","Use in pregnancy only if clearly needed (Pregnancy Category B)"] |
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| Fetal Monitoring | Monitor maternal symptoms of gastroesophageal reflux or peptic ulcer disease. No specific fetal monitoring required. Assess for adverse effects such as headache, dizziness, or constipation in the mother. |
| Fertility Effects | No adverse effects on fertility reported in animal studies. Human data insufficient to determine impact on fertility. |