Famotidine
Famotidine is a histamine-2 (H2) receptor antagonist. Famotidine is used for Active duodenal ulcer (US label), Active gastric ulcer (US label) and Symptomatic nonerosive GERD (US label).
Also called: Pepcid (United States) · Acid Controller (Canada)
Pronunciation: pronunciation varies by local usage.
- Generic name
- famotidine
- Drug class
- Histamine-2 (H2) receptor antagonist
- Form
- Film-coated tablets; the reviewed prescription labels cover 20 mg and 40 mg tablets (UK SPC covers the 20 mg film-coated tablet only)
- Route
- Oral
- Legal status
- Prescription-only tablet labelling covered in this draft; famotidine is also sold over the counter, but over-the-counter labelling was not reviewed in this pass
Availability and supply rules vary by country
Trade names by country: United States · Canada
Australia: · Full directory
What famotidine is and how it works
Famotidine is a histamine-2 (H2) receptor antagonist. It competitively inhibits H2 receptors and suppresses both the acid concentration and the volume of gastric secretion. Prescription tablet labelling covers a range of acid-related conditions; the exact list differs between the US and UK/EU labels. (3) (4)
Famotidine is available both on prescription and over the counter, and the directions differ. This draft covers only the prescription tablet label. Doses, permitted uses, minimum ages, and kidney-impairment advice differ between countries and are explained further in the professional information section; the prescriber sets the dose for each person.
Mechanism of action: how famotidine works
Famotidine is a competitive H2-receptor inhibitor; it suppresses both the acid concentration and the volume of gastric secretion. Pharmacokinetics from the US label: oral bioavailability 40–45%; peak plasma levels in 1 to 3 hours; elimination half-life 2.5 to 3.5 hours; eliminated 65–70% renally and 30–35% metabolically; 15–20% protein bound. (3) (4)
What is Famotidine used for?
Active duodenal ulcer (US label)
In adults and pediatric patients 40 kg and greater, the US prescription label lists active duodenal ulcer as an indication. (3)
Active gastric ulcer (US label)
In adults and pediatric patients 40 kg and greater, the US prescription label lists active gastric ulcer as an indication. (3)
Symptomatic nonerosive GERD (US label)
In adults and pediatric patients 40 kg and greater, the US prescription label lists symptomatic nonerosive gastro-oesophageal reflux disease as an indication. (3)
Erosive esophagitis due to GERD, diagnosed by biopsy (US label)
In adults and pediatric patients 40 kg and greater, the US prescription label lists erosive esophagitis due to GERD diagnosed by biopsy as an indication. (3)
Pathological hypersecretory conditions (US label, adults)
In adults, the US prescription label lists pathological hypersecretory conditions such as Zollinger-Ellison syndrome and multiple endocrine neoplasias. (3)
Reduction of the risk of duodenal ulcer recurrence (US label)
In adults, the US prescription label lists reduction of the risk of duodenal ulcer recurrence. (3)
UK/EU indications (differ from the US label)
The UK Summary of Product Characteristics lists: prevention of recurrent duodenal ulcers; duodenal ulcer; benign gastric ulcer; Zollinger-Ellison syndrome; and symptomatic treatment of mild reflux oesophagitis. These indications are narrower than, and differ from, the US prescription label, and the UK SPC states that the safety and efficacy of the 20 mg film-coated tablets in children has not been established, so children should not be treated with that product. (4)
Before taking famotidine
Do not take / not appropriate for
- Do not take famotidine tablets after a history of serious hypersensitivity (e.g. anaphylaxis) to famotidine or other H2 receptor antagonists, unless the prescriber has assessed this and determined otherwise under the exact local label. (prescription tablet label) (3) (4)
Tell your clinician about
- Any previous serious allergic reaction to famotidine or another H2 receptor antagonist, or to any tablet ingredient.
- Kidney problems or a known creatinine clearance value, because famotidine is mainly removed by the kidneys and dose reduction may be needed.
- Age (especially if elderly) and any confusion, delirium, hallucinations, disorientation, agitation, lethargy, or seizures, which have been reported in elderly patients and those with moderate-to-severe renal impairment.
- Whether you are or may be pregnant, or are breastfeeding.
- Every other medicine you take, including over-the-counter products, antacids, sucralfate, probenecid, and medicines for HIV, fungal infections, cancer, or muscle spasm (including tizanidine), because famotidine can change how some of these are absorbed or handled.
- Whether an ulcer has been confirmed and whether H. pylori status has been checked for duodenal or benign gastric ulcers.
- Any long-term high-dose treatment, because monitoring of blood count and liver function is recommended in that situation.
- Any plan to stop treatment after symptoms improve, especially in long-standing ulcer disease, because abrupt withdrawal after symptom relief should be avoided.
Famotidine dosage and how to take it
- Take the tablets by mouth. The US label states that once-daily dosing is taken before bedtime, or twice-daily dosing is taken in the morning and before bedtime, with or without food. The UK SPC states the film-coated tablets should be swallowed whole with some liquid and may be taken independently of meals.
- The prescriber sets the dose, the number of times a day, and the duration, based on the condition being treated, age, weight where relevant, and kidney function. Do not change the dose, frequency, or duration yourself.
- The 20 mg and 40 mg tablets are not recommended for children under 40 kg in the US label; a different formulation should be used. The UK 20 mg film-coated tablets should not be used in children at all.
- If an antacid is also used, the UK SPC states famotidine should be taken 1 to 2 hours before the antacid. If sucralfate is also used, the UK SPC states its use should be avoided within two hours of the famotidine dose.
- In case of long-standing ulcer disease, do not let treatment lapse abruptly after symptoms improve; discuss any plan to stop with the prescriber.
- For patients on dialysis, the UK SPC states the 20 mg film-coated tablets should be given at the end of, or after, dialysis.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (3) (2) (4)
Missed dose
The research notes for this medicine do not include a specific missed-dose instruction for famotidine. Contact the prescriber or pharmacist for advice on what to do about a missed dose. Do not take an extra dose to make up for a missed one without advice.
Overdose
The adverse reactions reported in overdose cases resemble those seen at recommended doses; treatment is supportive, and famotidine is removable by hemodialysis. In a US overdose situation, contact poison control at 1-800-222-1222 or emergency services. Patients with Zollinger-Ellison syndrome have tolerated doses up to 800 mg/day for more than a year without significant side effects. (3) (4)
Famotidine side effects
Frequencies below are from the UK Summary of Product Characteristics unless otherwise stated. Experience may differ between countries and products, and this page covers the prescription tablet label only.
Headache and dizziness
What to notice: Headache and dizziness are listed as common adverse reactions.
What to do: The UK SPC advises avoiding driving, operating machinery, or activities requiring prompt vigilance if you experience dizziness or headache. Discuss persistent or troublesome symptoms with the prescriber or pharmacist rather than stopping treatment yourself. (4)
Constipation and diarrhoea
What to notice: Constipation and diarrhoea are listed as common adverse reactions. The US label also lists headache, dizziness, constipation, and diarrhoea among the most common adverse reactions.
What to do: Discuss persistent or troublesome symptoms with the prescriber or pharmacist rather than stopping treatment yourself. (3) (4)
Fatigue, dry mouth, nausea and/or vomiting, abdominal discomfort or distension, flatulence
What to notice: These are listed as uncommon adverse reactions in the UK SPC.
What to do: Discuss persistent or troublesome symptoms with the prescriber or pharmacist rather than stopping treatment yourself. (4)
CNS effects
What to notice: Confusion, delirium, hallucinations, disorientation, agitation, lethargy, or seizures. Reported in elderly patients and those with moderate-to-severe renal impairment.
What to do: Seek medical attention promptly and let the clinician you see advise on whether to continue or stop, and on any dose reduction. Dosage reduction is recommended in renal impairment because blood levels are higher. (3)
Rare or very rare adverse reactions listed in the UK SPC
What to notice: Reversible psychic disturbances (including depression, anxiety disorders, agitation, disorientation, confusion, hallucinations, insomnia); convulsions or grand mal seizures (particularly in patients with impaired renal function); paresthesia, drowsiness, somnolence; blood count changes (leukopenia, thrombocytopenia, neutropenia, agranulocytosis, pancytopenia); hypersensitivity reactions (anaphylaxis, angioneurotic oedema, bronchospasm); interstitial pneumonia (sometimes fatal); liver enzyme abnormalities, hepatitis, cholestatic jaundice; rash, pruritus, urticaria, alopecia; Stevens-Johnson syndrome or toxic epidermal necrolysis (sometimes fatal); arthralgia or muscle cramps; impotence or reduced libido; chest tightness; increases in laboratory values (transaminases, gamma-GT, alkaline phosphatase, bilirubin); anorexia; dry mouth, dysgeusia.
What to do: Seek medical assessment promptly for any of these. (4)
Serious warnings
CNS adverse reactions, including in kidney impairment — serious
Symptoms: Confusion, delirium, hallucinations, disorientation, agitation, seizures, or lethargy, reported in elderly patients and those with moderate-to-severe renal impairment. The UK SPC also lists convulsions and grand mal seizures, particularly in patients with impaired renal function, and reversible psychic disturbances.
Action: Seek medical attention promptly. Dosage reduction is recommended in renal impairment because blood levels are higher, and the prescriber sets the dose; do not adjust the dose yourself. (3) (4)
Gastric malignancy not excluded by symptom response — serious
Symptoms: Symptomatic response to famotidine does not rule out gastric malignancy. Suboptimal response or early relapse may warrant evaluation.
Action: Discuss with the prescriber if symptoms respond poorly or relapse early. The UK SPC states gastric malignancy should be excluded before starting famotidine for gastric ulcer. (3) (4)
Serious hypersensitivity — emergency
Symptoms: Anaphylaxis, angioneurotic oedema, or bronchospasm. A history of serious hypersensitivity (e.g. anaphylaxis) to famotidine or other H2 receptor antagonists is a contraindication.
Action: Seek emergency care immediately for these symptoms. Let the clinician you see advise on whether to continue or stop famotidine. (3) (4)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Dasatinib, delavirdine, cefditoren, fosamprenavir | Famotidine may reduce the absorption of drugs that depend on gastric pH; co-administration with these is not recommended in the US label. | Tell the prescriber and pharmacist about all medicines. Follow the exact directions in the product information for each medicine. (3) |
| Atazanavir, erlotinib, ketoconazole, itraconazole, ledipasvir/sofosbuvir, nilotinib, rilpivirine | The US label refers to those products' own labels for recommendations on use with famotidine. The UK SPC states the absorption of ketoconazole and itraconazole could be reduced, and that ketoconazole should be given 2 hours before famotidine. The UK SPC also states that co-administration of posaconazole oral suspension with famotidine should be avoided if possible, and that co-administration with the TKIs dasatinib, erlotinib, gefitinib, and pazopanib is not recommended because their plasma concentrations may be decreased, resulting in lower efficacy. | Discuss timing and any need for alternative treatment with the prescriber and pharmacist before combining these medicines. (3) (4) |
| Tizanidine | Famotidine is a weak CYP1A2 inhibitor and may substantially raise tizanidine levels, which can cause hypotension, bradycardia, and excessive drowsiness. | Avoid taking famotidine and tizanidine together if possible; discuss alternatives with the prescriber. (3) |
| Antacids | Antacids may decrease the absorption of famotidine and lead to lower plasma concentrations. | The UK SPC states famotidine should be taken 1 to 2 hours before the antacid. (4) |
| Probenecid | Probenecid administration can delay the elimination of famotidine. | Concomitant use of probenecid and famotidine should be avoided. (4) |
| Sucralfate | The UK SPC notes a timing consideration for sucralfate. | The use of sucralfate should be avoided within two hours of the famotidine dose. (4) |
| Calcium carbonate used as a phosphate binder in haemodialysis patients | Risk of loss of efficacy of calcium carbonate when co-administered as a phosphate binder with famotidine in haemodialysis patients. | Discuss with the prescriber or pharmacist. (4) |
| Atazanavir, ritonavir, and tenofovir | If famotidine, atazanavir, and ritonavir are co-administered, a dose of 20 mg famotidine should not be exceeded. If a higher dose of famotidine is required (e.g. famotidine 40 mg), dose adjustment of atazanavir and ritonavir may be considered. Co-administration of famotidine, atazanavir, ritonavir, and tenofovir should be avoided; if judged unavoidable, close clinical monitoring is recommended. | Discuss this combination with the prescriber, who will set any dose adjustments. (4) |
| Medicines metabolised by cytochrome P450 (warfarin, theophylline, phenytoin, diazepam, propranolol, aminopyrine, antipyrine, phenprocoumon) and alcohol | The UK SPC states no drug interactions of clinical importance have been identified, famotidine does not interact with the cytochrome P450-linked drug metabolising enzyme system, and studies showed no augmentation of expected blood alcohol levels from alcohol ingestion. | Still give the prescriber and pharmacist a complete medicines list. (4) |
Special populations
Children and adolescents
The US label covers adults and pediatric patients 40 kg and greater for several indications, and the 20/40 mg tablets are not recommended for children under 40 kg (use another formulation). The UK SPC states that the safety and efficacy of the 20 mg film-coated tablets in children has not been established, so children should not be treated with that product. These labels differ, so the exact local product information must be used. (3) (4)
Older people
CNS adverse reactions such as confusion, delirium, hallucinations, disorientation, agitation, seizures, and lethargy have been reported in elderly patients. The UK SPC states that when famotidine was given to elderly patients in clinical trials, no increase in the incidence or change in the type of drug-related side effects was observed, and no dosage adjustment is required based on age alone. (3) (4)
Kidney impairment
Famotidine is mainly excreted via the kidneys, and dosage reduction is recommended in renal impairment because blood levels are higher. The US addendum gives lower maximum doses for kidney impairment, and the UK SPC recommends a 50% reduction in the daily dose when creatinine clearance is below 30 mL/min. For patients on dialysis, a 50% daily-dose reduction is also recommended, and the 20 mg film-coated tablets should be given at the end of, or after, dialysis. The prescriber sets the dose; do not adjust it yourself. (3) (4)
Pregnancy
The US label states available human data are insufficient to establish a drug-associated risk, and no adverse developmental effects were seen in animal studies at high multiples of the human dose. The UK SPC states famotidine is not recommended for use in pregnancy and should be prescribed only if clearly needed, weighing potential benefits against possible risks. Discuss with the prescriber. (3) (4)
Breastfeeding
The US addendum notes limited data on the presence of famotidine in human milk, with no effects observed on breastfed infants, and advises weighing benefits with the prescriber. The UK SPC states famotidine is detectable in human milk and that nursing mothers should either stop this drug or stop nursing. Discuss with the prescriber. (3) (4)
Monitoring
Before starting
- Confirm the exact diagnosis and which label's indications apply, because the US and UK/EU indication lists differ.
- Assess kidney function (for example creatinine clearance), since famotidine is mainly excreted by the kidneys and a dose reduction may be needed.
- For gastric ulcer, the UK SPC states gastric malignancy should be excluded before starting famotidine.
- For duodenal and benign gastric ulcers, the UK SPC states H. pylori status should be determined, and eradication therapy should be strived for in H. pylori-positive patients whenever possible.
- Assess history of serious hypersensitivity to famotidine or other H2 receptor antagonists.
- Review all other medicines, including over-the-counter products and medicines affected by gastric pH.
- Confirm the exact strength and formulation appropriate for the person, including weight for children.
During treatment
- Reassess symptoms and response, remembering that symptomatic response does not rule out gastric malignancy and that suboptimal response or early relapse may warrant evaluation.
- In case of long-term treatment with high dosage, the UK SPC recommends monitoring of blood count and liver function.
- In long-standing ulcer disease, the UK SPC states abrupt withdrawal after symptom relief should be avoided.
- Reassess kidney function where relevant, since dose reduction is recommended in renal impairment.
- Review all medicines for interactions, including pH-dependent absorption effects.
Storage
The research notes for this medicine do not include storage instructions for famotidine tablets. Follow the storage directions on the dispensing label and the product packaging, and ask the pharmacist if unsure.
Professional information
Clinician-facing context only. Use the current local indication, dosing table, formulation instructions, and background-disease guideline. Over-the-counter famotidine labelling was not reviewed in this pass and must not be inferred from this page.
United States
Indication: US prescription tablet label, adults and children 40 kg and greater, normal kidney function
Dose summary: Active duodenal ulcer: 40 mg once daily or 20 mg twice daily (up to 8 weeks). Active gastric ulcer: 40 mg once daily (up to 8 weeks). Symptomatic non-erosive GERD: 20 mg twice daily (up to 6 weeks). Erosive oesophagitis: 20 mg or 40 mg twice daily. Reducing duodenal ulcer recurrence: 20 mg once daily. Pathological hypersecretory conditions (adults): start 20 mg every 6 hours, adjusted, up to 160 mg every 6 hours. Take once daily before bedtime, or twice daily morning and before bedtime, with or without food. The 20/40 mg tablets are not recommended for children under 40 kg (use another formulation).
Renal context: Kidney impairment: lower maximum doses — e.g. creatinine clearance 30–60 mL/min: generally 20 mg once daily (or 40 mg every other day); under 30 mL/min: generally 20 mg every other day. Avoid in pathological hypersecretory conditions with kidney impairment. Prescriber sets the dose. (3)
United Kingdom / EU
Indication: Famotidine 20 mg film-coated tablets
Dose summary: Adults and the elderly. Duodenal ulcers and benign gastric ulcers: 40 mg once before going to bed. Prophylactic treatment of recurrent duodenal ulcers: 20 mg in the evening. Zollinger-Ellison syndrome: if no preceding treatment with secretion-inhibiting medicines, initiate with 20 mg every 6 hours; further doses adjusted according to the extent of acid secretion and the patient's clinical response until acid secretion is reduced to an acceptable level (e.g. <10 mEq/h the hour before the next famotidine dose). If a dosage of 800 mg/day does not result in sufficient inhibition of acid secretion, an alternative therapy should be considered, because there is no experience with long-term doses higher than 800 mg/day. Patients previously treated with other H2-receptor antagonists can change immediately to a higher initial dose than that recommended for new patients, dependent on the severity of the clinical picture and the prior dose. Symptomatic treatment of mild reflux oesophagitis: one 20 mg twice daily. Duration: duodenal and benign gastric ulcers 4 to 8 weeks, shorter if healing is endoscopically proved, or continued for another 4 weeks if not healed endoscopically after 4 weeks; maintenance 20 mg has been continued effectively in clinical studies of 12 months duration; mild reflux oesophagitis generally 6 weeks, if necessary 12 weeks; Zollinger-Ellison syndrome continued as long as clinically necessary. Swallow whole with some liquid; tablets may be taken independently of meals. The safety and efficacy of the 20 mg film-coated tablets in children has not been established; children should not be treated with this product.
Renal context: Famotidine is mainly excreted via the kidneys. In patients with impaired kidney function whose creatinine clearance is less than 30 mL/min (serum creatinine above 3.0 mg/100 mL), a reduction of the daily dose to 50% is recommended; for patients under dialysis, a 50% reduction is also recommended, and the 20 mg film-coated tablets should be given at the end or after dialysis because part of the active ingredient is removed during dialysis. (4)
Hepatic guidance
The UK SPC recommends monitoring of blood count and liver function in case of long-term treatment with high dosage, and lists liver enzyme abnormalities, hepatitis, and cholestatic jaundice among very rare adverse reactions. The research notes do not provide impairment-specific dosing for hepatic impairment; this page does not provide it.
Overdose note
Overdose adverse reactions resemble those at recommended doses; treatment is symptomatic and supportive; famotidine is removable by hemodialysis. Patients with Zollinger-Ellison syndrome have tolerated doses up to 800 mg/day for more than a year without significant side effects. (3) (4)
Frequently asked questions
Are over-the-counter and prescription famotidine the same thing?
Famotidine is sold both on prescription and over the counter, but the directions differ. This page covers the prescription tablet label only; over-the-counter labelling was not reviewed, so over-the-counter directions should be taken from that product's own label or a pharmacist. (3) (4)
Do I need a dose change if I have kidney problems?
Famotidine is mainly removed by the kidneys, and dosage reduction is recommended in renal impairment because blood levels are higher. The prescriber sets the dose; do not change it yourself. (3) (4)
Can famotidine interact with other medicines?
Yes. It may reduce the absorption of medicines that depend on gastric pH, and it is a weak CYP1A2 inhibitor that may substantially raise tizanidine levels. There are also timing rules with antacids and sucralfate and cautions with probenecid and some HIV medicines. Give the prescriber and pharmacist a full medicines list. (3) (4)
Can I drive while taking famotidine?
The UK SPC advises avoiding driving, operating machinery, or activities requiring prompt vigilance if you experience dizziness or headache while taking famotidine. (4)
What is the mechanism of action of famotidine?
Famotidine is a competitive H2-receptor inhibitor; it suppresses both the acid concentration and the volume of gastric secretion. Pharmacokinetics from the US label: oral bioavailability 40–45%; peak plasma levels in 1 to 3 hours; elimination half-life 2.5 to 3.5 hours; eliminated 65–70% renally and 30–35% metabolically; 15–20% protein bound. (3) (4)
References
- Famotidine tablet (prescription) — prescribing informationDailyMed, U.S. National Library of Medicine (prescribing information, SPL effective 2025-10-22) · United States · dated 2025-10-22 · accessed 2026-10-09 · source 1
- Famotidine: MedlinePlus Drug InformationMedlinePlus, U.S. National Library of Medicine · United States · accessed 2026-10-09 · source 2
- Famotidine tablets 20 mg/40 mg — prescribing information (addendum, exact US label wording)DailyMed, U.S. National Library of Medicine (prescribing information addendum, SPL effective 2025-10-22) · United States · dated 2025-10-22 · accessed 2026-10-12 · source 3
- Famotidine 20 mg film-coated tablet — Summary of Product Characteristicselectronic Medicines Compendium (UK) · United Kingdom · accessed 2026-10-17 · source 4
Brand names by country
Single-ingredient famotidine names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- Zantac 360tablet, film coated · 20 mg · lil' drug store products, incregulator source
- Pepcid ACtablet, film coated · 20 mg, 10 mg · lil' drug store products, inc.regulator source
- Pepcidtablet, film coated · 20 mg, 40 mg · bausch health us llcregulator source
Canada
- FAMOTIDINE OMEGAregulator source
- PEPCID ACregulator source
- MAXIMUM STRENGTH PEPCID ACregulator source
- ACID CONTROLLERregulator source