Famotidine
Administration
- Type: Histamine H2 blocker
- Dosage Forms: 10, 20, and 40 PO; 40/5 mL suspension
- Routes of Administration: PO, IV
- Common Trade Names: Pepcid, Pepcid AC
Adult Dosing
- Active duodenal ulcer
- 40mg PO qhs x4-6 weeks
- Alt dosing: 20mg PO BID or 20mg IV q12 hr
- Maintenance duodenal ulcer
- 20mg PO qhs
- Gastric ulcer
- 40mg PO qhs
- Alt dosing: 20mg IV q12 hr
- 20-40mg PO BID x12 weeks
- Alt dosing: 20mg IV q12 hr
- Zollinger-Ellison syndrome
- 20-60mg PO q6 hr
- Alt dosing: 20mg IV q12 hr
- Max: 160mg PO q6 hr
- intractable ulcer
- 20mg IV q12 hr
- H. pylori infection
- 20mg PO BID x 10-28 days
- Use in combination with other medications for eradication
Pediatric Dosing
- 1-16 years old
- 0.5-1mg/kd/day PO daily-bid
- Start at 0.5mg/kg/day daily-bid
- Alt dosing: 0.5-1mg/kg/day IV bid
- Max 40mg/day
- <3 mo
- 0.5mg/kg/day PO daily
- 3-12 mo
- 1mg/kg/day PO bid
- 1-16 yo
- 1-2mg/kg/day PO bid
- Start 1mg/kg/day bid
- Alt dosing: 0.5-1mg/kg/day IV bid
- Max 40mg/day
Special Populations
- Pregnancy Rating: B
- Lactation risk: Probably safe
Renal Dosing
- Adult: CrCl<50: decrease dose by 50% or give q 36-48 hr; If on dialysis give after dialysis
- Pediatric: CrCl 10-50: decrease dose 50% or give q24 hr, CrCl<10: give q36-48 hr
Hepatic Dosing
- Adult: Not defined
- Pediatric:Not defined
Contraindications
- Allergy to class/drug
- Caution in renal impairment
Adverse Reactions
Serious
- Anaphylaxis
- Angioedema
- TEN
- Stevens-Johnson Syndrome
- agranulocytosis
- leukopenia
- thrombocytopenia
- pancytopenia
- seizures
- AV block
- arrhythmias
- CNS toxicity
- cholestatic jaundice
- hepatitis
- interstitial pneumonia
- QT prolongation
Common
- headache
- dizziness
- constipation
- diarrhea
- taste changes
- vitamin B12 deficiency
Pharmacology
- Half-life: 2.5-3.5 hr; >20 hr with CrCl<10
- Metabolism: minimally liver/CYP450
- Excretion: urine
Mechanism of Action
- Selective histamine H2 blocker