Adults

For GERD: 20 mg or 40 mg twice daily for up to 6-12 weeks. For duodenal ulcer: 40 mg once daily at bedtime for 4-8 weeks. For gastric ulcer: 40 mg once daily at bedtime for 6-8 weeks. For Zollinger-Ellison Syndrome: Initial dose 20 mg every 6 hours; dosage may be adjusted based on acid output.

Elderly

No specific dose adjustment is generally required, but caution is advised in patients with renal impairment.

Renal_impairment

For creatinine clearance < 10 mL/min: reduce dose to 20 mg once daily or every other day, depending on the patient's response and tolerability. For severe impairment, consider reducing dose by 50% or increasing dosing interval to 36-48 hours.

Onset

Within 1 hour

Excretion

Primarily renal excretion, with 65-70% of the orally administered dose excreted unchanged in urine.

Half life

2.5-3.5 hours (prolonged in renal impairment)

Absorption

Rapidly absorbed after oral administration. Bioavailability is approximately 40-45%. Peak plasma concentrations occur within 1-3 hours.

Metabolism

Approximately 25-30% is metabolized in the liver to an inactive sulfoxide metabolite.

Antacids

May decrease the absorption of famotidine. Administer famotidine 1-2 hours before antacids.

Atazanavir

Reduced absorption due to pH increase. Co-administration is generally not recommended or requires specific timing/dosing.

Cefpodoxime

Famotidine may decrease the absorption of cefpodoxime. Separate administration times.

Ketoconazole, Itraconazole

Famotidine can reduce the absorption of these drugs, which require an acidic gastric pH for absorption. Administer famotidine several hours after these antifungals.