Famotidine
- Drugs List
- Therapeutic Indications
- Dosage
- Contraindications
- Precautions and Warnings
- Pregnancy and Lactation
- Side Effects
- Monograph
Drugs List
Therapeutic Indications
Uses
Duodenal ulcer
Prevention of relapse of duodenal ulceration
Benign gastric ulcer
Hypersecretory conditions such as Zollinger-Ellison syndrome
Treatment of gastro-oesophageal reflux disease
Prevention of relapse of symptoms and erosions or ulcerations associated with gastro-oesophageal reflux disease
Dosage
Adults
Duodenal ulcer:
The recommended initial dose is one 40mg tablet at night. Treatment should continue for 4 - 8 weeks. In most patients, healing occurs on this regimen within 4 weeks. In those patients whose ulcers have not healed completely after 4 weeks, a further 4 week period of treatment is recommended. For preventing the recurrence of duodenal ulceration, the reduced dose of 20mg at night is recommended.
Benign gastric ulcer:
The recommended dose is one 40mg tablet at night. Treatment should continue for 4 - 8 weeks unless endoscopy reveals earlier healing.
Zollinger-Ellison syndrome:
Patients without prior antisecretory therapy should be started on 20mg every 6 hours. Dosage should then be adjusted to individual response. Doses up to 800mg daily have been used up to 1 year without the development of significant adverse effects or tachyphylaxis. Patients who have been receiving another H2 antagonist may be switched directly to famotidine at a dose higher than that recommended for new cases. The starting dose will depend on the severity of the condition and the last dose of H2 antagonist previously used.
Gastro-oesophageal reflux disease:
The recommended dosage for the symptomatic relief of gastro-oesophageal reflux disease is 20mg of famotidine twice daily, which may be given for 6 to 12 weeks. Most patients experience improvement after 2 weeks.
Where gastro-oesophageal reflux disease is associated with the presence of oesophageal erosion or ulceration, the recommended dosage is 40mg of famotidine twice daily, which may be given for 6 to 12 weeks.
For the prevention of recurrence of symptoms and erosions or ulcerations associated with gastro-oesophageal reflux disease, the recommended dosage is 20mg of famotidine twice daily.
Elderly
No dosage adjustment is necessary (see 'Dosage - Adults')
Caution is advised in the elderly due to the increased possibility of renal impairment.
Children
Patients with Renal Impairment
To avoid excess accumulation of the drug in patients with moderate or severe renal insufficiency, the dose of famotidine may be reduced to half the dose or the dosing interval may be prolonged to 36-48 hours as indicated by the patient's clinical response.
The Renal Drug Handbook suggests the following dosage adjustment:
GFR 20-50 ml/min = dose as in normal renal function
GFR 10-20 ml/min = half of normal dose
GFR less than 10 ml/min = 20mg at night (maximum)
Contraindications
Children under 18 years.
Precautions and Warnings
Gastric malignancy should be excluded prior to initiation of therapy of gastric ulcer with famotidine. Symptomatic response of gastric ulcer therapy with famotidine does not preclude the presence of gastric malignancy.
Since famotidine is excreted primarily by the kidney, caution should be observed in patients with severe renal impairment. Dosage adjustment is necessary in patients with glomerular filtration rate less than 20ml/min. (see 'Dosage - Renal impairment' section)
During long term treatment with high dose famotidine, monitoring of blood count and liver function is recommended.
In patients with long standing ulcer disease, abrupt withdrawal after symptom relief should be avoided.
Pregnancy (see 'Pregnancy' section)
Breastfeeding (see 'Lactation' section)
Elderly (see 'Dosage - Elderly' section)
Pregnancy and Lactation
Pregnancy
Famotidine is well absorbed and crosses the placental barrier. There is very little experience in the use of famotidine in pregnancy but that there are no indications of a teratogenic risk in humans as yet. Animal studies in rats and rabbits found no evidence of impaired fertility, fetotoxic effects, teratogenicity or changes in postnatal behaviour attributable to famotidine. Other drugs of the same class that have been studied more extensively may be preferred to famotidine.
The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14-17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password at ( https://www.toxbase.org/ ) or if this is unavailable at the backup site ( https://www.TOXBASEbackup.org/ ).
Lactation
Famotidine is excreted in breast milk but to a lesser degree than either cimetidine or ranitidine and as such may be preferred to other H2 receptor antagonists. LactMed (via Toxnet) also concludes that famotidine would not be expected to cause any adverse effects in breastfed infants.The manufacturer recommends that because famotidine is excreted in breast milk, breast feeding mothers should either stop breast feeding or stop taking the drug.
Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
Specialist advice is available from the UK Drugs in Lactation Advisory Service at https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1
Effects on Ability to Drive and Operate Machinery
Patients should be advised that they should avoid driving or operating machinery if they experience symptoms such as dizziness and headache.
Side Effects
Headache
Dizziness
Constipation
Diarrhoea
Dry mouth
Nausea
Vomiting
Abdominal discomfort
Abdominal distension
Anorexia
Fatigue
Rash
Pruritus
Urticaria
Alterations in hepatic enzymes
Cholestatic jaundice
Anaphylaxis
Angioedema
Arthralgia
Muscle cramps
Depression
Anxiety
Agitation
Reversible confusional states
Hallucinations
Toxic epidermal necrolysis
Pancytopenia
Leucopenia
Agranulocytosis
Thrombocytopenia
Neutropenia
Gynaecomastia
Atrioventricular block
Paraesthesia
Reduced libido
Insomnia
Interstitial pneumonia
Impotence
Dysgeusia
Stevens-Johnson syndrome
Grand mal seizure
Somnolence
Flatulence
Hepatitis
Alopecia
Bronchospasm
Chest tightness
Disorientation
Convulsions
Prolongation of QT interval
Hypersensitivity reactions
Overdosage
It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.
The following number will direct the caller to the relevant local centre (0844) 892 0111)
Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( https://www.toxbase.org/ ) or if this is unavailable at the backup site ( https://www.TOXBASEbackup.org/ ).
Shelf Life and Storage
Do not store above 25 degrees C
Reference Sources
British National Formulary, 60th Edition (2010) Pharmaceutical Press, London.
Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.
Summary of Product Characteristics: Pepcid 20mg and 40mg Tablets. Merck Sharp & Dohme Ltd. Revised February 2011.
The Renal Drug Handbook. 3rd edition. (2009) ed. Ashley, C and Currie, Radcliffe Publishing Ltd, Abingdon.
US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
Available at: https://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT
Famotidine. Last revised: February 28, 2011
Last accessed: March 21, 2011
Medscape UK | Univadis prescription drug monographs & interactions are based on FDB Multilex Content
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