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famotidine (Pepcid RPD / Pepcidin Rapitab / famotidine, Zydis)

✓ Approved

Merck & Co. · HRH2 · Small Molecule

What is famotidine?

famotidine is a small molecule developed by Merck & Co.. It is approved for therapeutic indications via oral (po).

Drug Profile

Brand NamesPepcid RPD, Pepcidin Rapitab, famotidine, Zydis
CompanyMerck & Co.
Drug ClassSmall Molecule
Molecular TargetHRH2
RouteOral (PO)
StatusApproved
Sources: ClinicalTrials.gov, Merck & Co.

Mechanism of Action

Molecular Targets

famotidine acts on 1 molecular target:

HRH2histamine receptor H2 (H2R, HH2R)
Want deeper analysis?Noah AI can explain complex mechanisms and compare to similar drugs.

Therapeutic Indications

famotidine is developed for 3 unique indications across 1 therapeutic area.

Therapeutic AreaConditionPhase
Gastrointestinal disordersDuodenal ulcer✓ Approved
Gastrointestinal disordersGastric ulcer✓ Approved
Gastrointestinal disordersGastrooesophageal reflux disease✓ Approved

Related Research Articles

PubMedIndian journal of pharmacology2026-11-02

Proton-pump inhibitor-induced severe hypomagnesemia presenting with seizure and functional hypoparathyroidism: A diagnostic challenge in long-term acid suppression therapy.

Hassan Yasir Y, Sarjanya Gampa G, Duraiswamy Jegan J, Ram Prabu P

Proton-pump inhibitors (PPIs) are popular drugs used to treat acid-related disorders. The PPIs, though effective and relatively safe, have been linked to clinically significant hypomagnesemia with long-term use, which causes potentially life-threatening complications. A 68-year-old male with an 8-year history of omeprazole 40 mg/day use presented with a generalized tonic-clonic seizure and neuromuscular irritability. Laboratory tests showed severe hypomagnesemia (0.32 mmol/L), hypocalcemia (corrected calcium 1.62 mmol/L), hypokalaemia (3.2 mmol/L), and low parathyroid hormone (12 pg/mL). 24-h urine magnesium was low (12 mg/day), suggesting external magnesium loss. Serum Vitamin D levels and renal function tests were within normal limits. Electrocardiography showed Corrected QT (QTc) interval prolongation (510 ms) with ventricular ectopy. Magnesium levels failed to normalize despite intravenous replacement until omeprazole was discontinued and replaced with famotidine. PPI-induced hypomagnesemia should be suspected in patients on long-term therapy presenting with electrolyte disturbances, seizures, or arrhythmias. Recognition is crucial, as correction is often refractory until the offending drug is withdrawn.

PMID 42969997
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PubMedJournal of oncology pharmacy practice : official publication of the International Society of Oncology Pharmacy Practitioners2026-10-30

Administration-related reactions following first-dose subcutaneous daratumumab to inform implementation of a 30-minute observation period.

Galvet Jennifer J, Kim Sara S SS, Caro Jessica J, Chung David J DJ

IntroductionSubcutaneous daratumumab has lower rates of administration-related reactions (ARRs) than intravenous daratumumab and shorter administration times. However, the optimal monitoring following the first dose remains uncertain and varies across institutions. This medication use evaluation assessed first-dose ARRs under a 2-h observation protocol and whether available findings support reduced 30-min observation.MethodsThis retrospective, single-center cohort study included patients who received first-dose subcutaneous daratumumab at the Zuckerberg Cancer Center between March 6, 2024, and July 31, 2025. The primary endpoint was ARR incidence. Secondary endpoints included time to onset, CTCAE version 6.0 severity, and management interventions. Premedication adherence and potential chair-time savings from reducing observation from 4 to 2 h were also evaluated. After implementation of the 30-min observation period, 26 additional patients treated from April through June 2026 were reviewed for ARRs.ResultsAmong 50 patients in the primary cohort, one experienced an ARR (2%). Grade 3 ARR occurred 150 min after administration and required intravenous methylprednisolone, diphenhydramine, famotidine, and intramuscular epinephrine. Premedication deviations included diphenhydramine 25 mg instead of 50 mg and omitted montelukast. The patient tolerated subsequent doses after receiving the complete regimen. No ARRs occurred among the 26 patients evaluated after implementation of 30-min observation.ConclusionFirst-dose subcutaneous daratumumab was associated with a low ARR incidence, with the only reaction occurring beyond 2 h. Together with published evidence and institutional experience, these findings supported implementation of 30-min observation, with no ARRs observed after implementation. Larger studies with longer follow-up are warranted to further assess abbreviated observation.

PMID 42957977
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PubMedJournal of clinical densitometry : the official journal of the International Society for Clinical Densitometry2026-10-28

Association between long-term proton pump inhibitor use and bone mineral density among Jordanian adults: A retrospective study.

Massad Mu'taz M, Alqoudah Mais M, Saleh Zain Aldeen ZA, Hizzani Younis Y et al.

Osteoporosis is a common skeletal disease that is defined by low bone density and an increased risk of fracture. It is a widespread health issue with significant health consequences that has recently attracted the attention of the worldwide community. The present research was carried out to test the association between prolonged PPI therapy and bone mineral density among patients in Jordan. A retrospective observational study was performed at Al-Zarqa New Governmental and Al-Basheer Hospitals, Jordan. A total of 695 patients aged 20-60 years who underwent dual-energy X-ray absorptiometry (DEXA) were divided into 3 groups: long-term users of PPIs (≥ 12 months), famotidine users (≥ 12 months), and non-users. Bone mineral density (BMD) at the lumbar spine and femoral neck was measured using T- and Z-scores adjusted for age and sex. Of 695 participants, 180 (25.9%) were PPI users, 105 (15.1%) famotidine users, and 410 (59%) non-exposed group. The median age was 53 years, and 90.4% were female. No significant differences were found in femoral neck or lumbar spine BMD and Z-scores between groups. In the T-score group, the lumbar spine T-score differed significantly across groups (p = 0.040), driven by differences between non-exposed group and famotidine users (p = 0.034), with no significant differences involving PPI users. Our study provides the literature with unique results in support of the safety of long-term PPI use in terms of BMD. Further research is needed to explore this relationship in more robust study designs that address potential bias and confounding factors and explore it in a healthy population.

PMID 42950445
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PubMedActa crystallographica. Section C, Structural chemistry2026-10-26

Copper and cobalt complexes with famotidine.

Weaver MacKenzie C MC, Oliver Allen G AG, Barstis Toni L O TLO

This research contributes to the development of Paper-Based Analytical Devices (PADs) for screening low-quality famotidine, the active pharmaceutical ingredient in Pepcid AC. While three key colorimetric chemical tests - copper(II) sulfate, cobalt(II) thiocyanate, and nickel(II) chloride - are employed on these PADs, the underlying chemistry remains poorly understood. Here we report the successful isolation and structural characterization of two new crystalline colored famotidine-metal complexes generated during PAD activation. These are a green-colored famotidine-copper(II) chloride complex, (3-{[(2-carbamimidamido-1,3-thiazol-4-yl)methyl]sulfanyl}-N-sulfamoylpropanamide)dichloridocopper(II), [CuCl2(C8H14N6O3S3)], and a blue-colored famotidine propionic acid-cobalt(II) tetrachloride complex, bis(4-{[(2-carboxyethyl)sulfanyl]methyl}-N-(diaminomethylidene)-1,3-thiazol-2-aminium) tetrachloridocobaltate(II), (C8H13N4O2S2)2[CoCl4]. Elucidating these crystal structures provides critical insights into the chemistry occurring on the activated PADs, enabling further device development and optimization.

PMID 42931791
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PubMedJournal of veterinary pharmacology and therapeutics2026-10-25

Pharmacokinetics of Famotidine in Goats (Capra aegagrus hircus) After Subcutaneous Administration.

Escher-Price Olivia G OG, Smith Joe S JS, Christopher Kamryn K, Duncan Madeline M et al.

Small ruminants such as goats are susceptible to abomasal ulceration due to adverse reactions to medications, stress, and inappetence. There is limited pharmacokinetic data regarding the use of famotidine for treatment and prevention of abomasal ulceration in goats. The objective of this study is to report the pharmacokinetic parameters after a single subcutaneous administration of famotidine. Famotidine was administered at a 1.2 mg/kg dose to six healthy goats and plasma samples were collected over a 12-h period. The plasma was analyzed using reverse phase high performance liquid chromatography (HPLC) to measure famotidine concentrations. Using commercially available pharmacokinetic software, noncompartmental analysis was used to determine the pharmacokinetic parameters. The maximum plasma concentration was estimated at 735 ng/mL and the Tmax was 0.64 h. The apparent terminal half-life was 1.29 h, and the mean residence time was 1.82 h. The area under the curve was found to be 1046 h*ng/mL. Five of the 6 goats in this study had been utilized for a previous intravenous famotidine investigation, and when comparing the area under the curve to this study, the range of the estimated bioavailability after subcutaneous administration was 21.43%-135%. Future research performing a pharmacodynamic study measuring the pH of the abomasal fluid could be used to determine the efficacy of famotidine on raising pH levels. Compared to other studies with intravenous administration in goats, subcutaneous administration of famotidine may be a more useful way of maintaining concentrations over time.

PMID 42921682
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PubMedCureus2026-10-25

Allergic to Exercise: A Case of Exercise-Induced Urticaria and Angioedema.

Patel Puja P

A 23-year-old female presented with urticaria, peri-orbital angioedema, wheeze and cough during intense exercise, with progression slowed by exercise cessation. Additional triggers included passive heating and strong emotion, while low-to-moderate intensity exercise did not provoke symptoms. Symptoms occurred independently of food intake. Past medical history included exercise-induced bronchoconstriction (EIB), eczema and seasonal allergies. Skin-prick and specific IgE testing for food allergens were negative, whilst dermatographia testing was positive. Specific IgE testing demonstrated sensitisation to house dust mite and animal dander as well as several moulds. Initial treatment with antihistamines, famotidine and montelukast provided partial symptom control, whilst later addition of omalizumab resulted in resolution of exercise-induced urticaria and angioedema. This case illustrates the diagnostic overlap between exercise-induced anaphylaxis (EIA), a rare, life-threatening syndrome associated with exercise, and cholinergic urticaria, with a possible contribution from symptomatic dermographism and pre-existing symptoms of EIB. This case highlights that exercise-triggered urticarial syndromes may not fit neatly into a single diagnostic category, and that a thorough, trigger-focused history remains a valuable diagnostic tool.

PMID 42927275
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