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Famotidine (Pepcid)

H2 Blockeroral · inferred

H2 receptor antagonist that reduces stomach acid production. Faster onset but shorter duration of action compared to proton pump inhibitors.

Projected serum levels — 20 mg, twice daily

Famotidine (Pepcid)
Famotidine (Pepcid) modeled serum levels, 20 mg twice daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 1 days. 0 2.5 5 7.5 10 Day 0 Day 4 Day 7 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 1

Maintenance schedule: 20 mg twice daily (oral).

Modeled steady state after ~1 days: peak ≈ 6.2 mg, trough ≈ 0.80 mg body load. Population-based estimate over 15 days for a 20 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
H2 Blocker
Route modeled
Oral
Model confidence
inferred
Half-life
3 h
Common dose
20 mg
Suggested maximum
80 mg/day
Reference dose range
10–80 mg (single dose)
Suggested cadence
twice daily
Validated against
40 mg oral — Cmax 0.085 mg/L at 2 h

Documented interactions

  • caution
    Iron (Bisglycinate) + Famotidine (Pepcid) Depletion

    H2 blockers reduce gastric acid needed for non-heme iron absorption.

  • caution
    Itraconazole (Sporanox) + Famotidine (Pepcid) stomach ph

    Famotidine (Pepcid) raises gastric pH, which may reduce absorption of Itraconazole (Sporanox) (antifungal — requires gastric acid for dissolution).

  • caution
    Levothyroxine (Synthroid) + Famotidine (Pepcid) stomach ph

    Famotidine (Pepcid) raises gastric pH, which may reduce absorption of Levothyroxine (Synthroid) (thyroid hormone — absorption pH-dependent).

  • caution
    Mycophenolate Mofetil (CellCept) + Famotidine (Pepcid) stomach ph

    Famotidine (Pepcid) raises gastric pH, which may reduce absorption of Mycophenolate Mofetil (CellCept) (immunosuppressant — dissolution pH-dependent).

  • caution
    Rilpivirine (RPV / Edurant) + Famotidine (Pepcid) stomach ph

    Famotidine (Pepcid) raises gastric pH, which may reduce absorption of Rilpivirine (RPV / Edurant) (NNRTI — absorption reduced at elevated pH).

  • caution
    Vitamin B12 (Cobalamin) + Famotidine (Pepcid) Depletion

    H2 blockers reduce stomach acid, impairing B12 liberation from food. Less severe than PPIs but still relevant long-term.

Serum checks 8 modeled interaction pairings for famotidine (pepcid) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Famotidine, a new H2-receptor antagonist: a review of preclinical and clinical studies Takeda M et al. · Drugs, 1986 DOI

    Foundational review establishing famotidine as 20-50 times more potent than cimetidine at the H2 receptor, with excellent safety profile and once or twice daily dosing.

  2. Famotidine use is associated with improved clinical outcomes in hospitalized COVID-19 patients: a propensity score matched retrospective cohort study Freedberg DE et al. · Gastroenterology, 2020 DOI

    Retrospective study of hospitalized COVID-19 patients found famotidine use was associated with reduced risk of clinical deterioration, intubation, or death.

  3. Comparison of famotidine with ranitidine for treatment of patients with gastric or duodenal ulcers Texter EC et al. · Digestive Diseases and Sciences, 1987 DOI

    Multicenter trial found famotidine 40 mg at bedtime was as effective as ranitidine 150 mg twice daily for healing gastric and duodenal ulcers.

3 published studies referenced in the app, each with a plain-language summary.