FAMOTIDINE PRESERVATIVE FREE (PHARMACY BULK)
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 in gastric parietal cells, inhibiting gastric acid secretion.
| Metabolism | Metabolized by CYP450 enzymes (minor extent); primarily undergoes renal excretion with some hepatic metabolism to famotidine S-oxide. |
| Excretion | Renal (65-70% unchanged); biliary/fecal (30-35%) |
| Half-life | 2.5-3.5 hours; prolonged in renal impairment (CrCl <10 mL/min: 12-20 hours) |
| Protein binding | 15-20% (primarily albumin) |
| Volume of Distribution | 1.0-1.4 L/kg; indicates distribution into total body water |
| Bioavailability | IV: 100%; oral: 40-45% (first-pass metabolism) |
| Onset of Action | IV: within 30 minutes; oral: 1-2 hours |
| Duration of Action | IV: 10-12 hours (acid suppression); oral: 10-12 hours (continuous therapy) |
20 mg IV every 12 hours or 40 mg IV every 24 hours; may increase to 20 mg IV every 6 hours if needed. Infuse over 15-30 minutes (final concentration ≤4 mg/mL).
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 10-50 mL/min: reduce dose by 50% or extend interval to every 24-36 hours. CrCl <10 mL/min: administer 50% of normal dose or extend interval to every 48 hours. |
| Liver impairment | No dose adjustment required for mild-to-moderate hepatic impairment. Severe hepatic impairment (Child-Pugh C): consider dose reduction by 50% due to reduced clearance. |
| Pediatric use | Children ≥1 year: 0.5 mg/kg IV every 12 hours (max 20 mg/dose) or 1 mg/kg IV every 24 hours (max 40 mg/dose). Infuse over at least 2 minutes. |
| Geriatric use | Lower initial dose (e.g., 20 mg IV every 24 hours) due to age-related renal function decline; titrate based on CrCl and clinical response. Monitor for confusion, especially in elderly with comorbidities. |
| 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; the milk-to-plasma ratio (M/P) is approximately 1.78. The estimated infant dose is about 6.4% of the maternal weight-adjusted dose, which is below the 10% threshold considered potentially concerning. Famotidine is generally considered compatible with breastfeeding, but caution is advised for preterm infants or those with renal impairment due to the potential for accumulation. |
| Teratogenic Risk |
■ FDA Black Box Warning
None.
| Common Effects | GERD |
| Serious Effects |
["Hypersensitivity to famotidine or other H2 receptor antagonists","Severe renal impairment (CrCl <10 mL/min) unless dose adjusted"]
| Precautions | ["Renal impairment requires dose adjustment","Possible cross-sensitivity in patients with history of hypersensitivity to other H2 receptor antagonists","May mask symptoms of gastric malignancy","Use in pregnancy only if clearly needed (Pregnancy Category B)","Use with caution in elderly due to increased risk of adverse effects","Possible risk of Clostridium difficile-associated diarrhea with prolonged use"] |
Loading safety data…
| Famotidine is classified as FDA Pregnancy Category B. In the first trimester, data from large epidemiological studies (including over 1,000 exposed pregnancies) do not show an increased risk of major congenital malformations. In the second and third trimesters, there is no evidence of fetal harm. Animal studies have not demonstrated teratogenicity at doses up to 2000 mg/kg/day in rats and 200 mg/kg/day in rabbits. |
| Fetal Monitoring | No specific fetal monitoring is required beyond routine prenatal care. Clinical monitoring for maternal adverse effects (e.g., headache, dizziness, constipation) is standard. In neonates, no specific monitoring is indicated unless maternal use was prolonged or at high doses near delivery. |
| Fertility Effects | Based on animal studies, famotidine had no adverse effects on fertility in rats at oral doses up to 2000 mg/kg/day. No human data suggest impairment of fertility. Thus, famotidine is not expected to adversely affect male or female fertility. |