FAMOTIDINE PRESERVATIVE FREE
Clinical safety rating: safe
No significant drug interactions May cause confusion more commonly in elderly or severely ill patients.
Competitive antagonist of histamine at H2 receptors on gastric parietal cells, inhibiting basal and stimulated gastric acid secretion.
| Metabolism | Minimal hepatic metabolism; primarily excreted unchanged via renal tubular secretion. Minor metabolites include famotidine S-oxide. |
| Excretion | Renal: 65-70% unchanged; hepatic metabolism: 30-35% (S-oxide metabolite); fecal: <5% |
| Half-life | 2.5-3.5 hours; prolonged in renal impairment (CrCl <10 mL/min: up to 20 hours) |
| Protein binding | 15-20%; primarily to albumin |
| Volume of Distribution | 1.1-1.4 L/kg; widely distributed, including into cerebrospinal fluid (low levels) |
| Bioavailability | Oral: 40-45%; IV: 100% |
| Onset of Action | IV: 30 minutes; oral: 60 minutes |
| Duration of Action | IV: 10-12 hours; oral: 12-24 hours (dose-dependent, as acid suppression persists beyond half-life) |
20 mg IV every 12 hours or 40 mg IV once daily; may also be administered as continuous IV infusion at 20 mg over 24 hours after an initial loading dose of 20 mg.
| Dosage form | INJECTABLE |
| Renal impairment | For CrCl < 50 mL/min: reduce dose to 50% or extend dosing interval to every 24-36 hours; for CrCl < 10 mL/min: 20 mg IV every 36-48 hours. |
| Liver impairment | No dosage adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). For severe hepatic impairment (Child-Pugh C), use with caution; no specific dosing guidelines available; consider reduced dose or extended interval. |
| Pediatric use | Infants < 3 months: 0.5 mg/kg IV once daily. Children 3 months to < 1 year: 0.5 mg/kg IV every 12 hours. Children 1-16 years: 0.5 mg/kg IV every 12 hours (max 20 mg/dose). |
| Geriatric use | No specific dose adjustment solely for age; consider renal function and potential increased sensitivity; start at lower end of dosing range (e.g., 20 mg IV once daily) and titrate based on response and tolerability. |
| 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 into human breast milk in low concentrations. M/P ratio approximately 1.78 (range 0.94–2.95). Infant dose estimated at <1% of maternal weight-adjusted dose. Compatible with breastfeeding. |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of teratogenicity in animal studies. Limited human data; no increased risk of major malformations reported with use during all trimesters. Considered low risk. |
■ FDA Black Box Warning
None
| Common Effects | GERD |
| Serious Effects |
Hypersensitivity to famotidine or other H2 receptor antagonists. Not contraindicated in pregnancy per FDA pregnancy category B, but caution in nursing mothers.
| Precautions | Risk of acute pancreatitis, QT prolongation (in patients with renal impairment or concurrent QT-prolonging drugs), altered mental status (especially in elderly or renally impaired), and thrombocytopenia. Adjust dose in severe renal impairment (CrCl <50 mL/min). Avoid use in patients with history of acute porphyria. |
Loading safety data…
| Fetal Monitoring | No specific fetal monitoring required. Monitor maternal renal function in prolonged use. |
| Fertility Effects | No adverse effects on fertility in animal studies. No human data indicating impaired fertility. |