Famotidine

Famotidine is a histamine H2 receptor antagonist used to reduce the production of stomach acid. It is prescribed for a range of acid-related conditions, including peptic ulcers, gastro-oesophageal reflux disease (GORD), and the hypersecretory condition known as Zollinger-Ellison syndrome. In lower doses, famotidine is also available over the counter for the relief of heartburn and indigestion.

How Famotidine Works

The parietal cells of the stomach lining produce acid in response to several stimuli, one of which is the binding of histamine to H2 receptors on their surface. Famotidine competitively and reversibly blocks these H2 receptors, thereby reducing the secretion of hydrochloric acid both when the stomach is empty (basal secretion) and in response to food, caffeine, or other triggers. By lowering acid output, famotidine allows the stomach and oesophageal lining to heal and reduces the symptoms of acid-related disorders. It is effective, well tolerated, and generally produces fewer drug interactions than older H2 antagonists such as cimetidine.

Clinical Applications

Famotidine is used for the treatment and prevention of gastric and duodenal ulcers, including ulcers associated with non-steroidal anti-inflammatory drug (NSAID) use. It is prescribed for GORD, both for symptom relief and for healing oesophagitis when present. At higher doses, it is used to manage the excessive acid secretion characteristic of Zollinger-Ellison syndrome, a rare condition caused by gastrin-secreting tumours. In hospitalised patients, famotidine may be used to prevent stress ulcers.

Formulation and Convenience

Famotidine is available as prescription-strength tablets (20 mg and 40 mg) and in lower-dose formulations available over the counter for self-management of heartburn. It has a rapid onset of action, with acid suppression beginning within one to three hours of an oral dose and lasting for up to twelve hours, making it suitable for twice-daily or once-nightly dosing depending on the indication.

How to Take Famotidine

Famotidine can be taken with or without food. For most indications, a single 20 mg dose twice daily or 40 mg once daily at bedtime is used. Taking the evening dose at bedtime takes advantage of the need to suppress nocturnal acid secretion, which drives overnight ulcer symptoms and healing.

For peptic ulcer disease, treatment courses of four to eight weeks are typical. For gastro-oesophageal reflux disease (GORD), famotidine 20 mg twice daily for up to twelve weeks is standard. For maintenance to prevent ulcer recurrence, 20 mg at night is used long-term.

Over-the-counter Use

Famotidine is also available over the counter at lower doses for self-treatment of heartburn and indigestion. If symptoms persist beyond two weeks of self-treatment, see your doctor for a full assessment.

Famotidine dosing varies by indication. For active duodenal or gastric ulcers, the standard dose is 40 mg once daily at bedtime or 20 mg twice daily for four to eight weeks. Maintenance therapy to prevent relapse is 20 mg at bedtime taken long term.

For GORD, the usual dose is 20 mg twice daily for up to eight weeks. For Zollinger-Ellison syndrome, treatment starts at 20 mg every six hours and may be increased based on acid output measurements; some patients require doses well above the standard range.

For OTC heartburn relief, doses of 10 to 20 mg are taken as needed, usually no more than twice daily for a maximum of two weeks without medical review.

Renal impairment requires dose adjustment: when creatinine clearance falls below 50 mL/min, the dosing interval should be extended to every 36 to 48 hours, or the dose halved, to avoid accumulation. No dose adjustment is necessary for hepatic impairment alone. Elderly patients generally tolerate standard doses but should be monitored for CNS side effects such as confusion, which are more likely in those with impaired renal function.

Common Side Effects

Famotidine is one of the better-tolerated acid-reducing medicines. The most frequently reported side effects include:

• Headache
• Dizziness
• Constipation
• Diarrhoea
• Nausea or vomiting
• Dry mouth
• Fatigue

These effects are usually mild and temporary.

When to Seek Advice

Seek urgent medical attention if you develop new difficulty swallowing, persistent vomiting, unexplained weight loss, blood in vomit or stools, or symptoms that return quickly after stopping treatment. These symptoms may indicate a more serious underlying condition that requires endoscopy or specialist review — they should not be managed with ongoing acid suppression alone without investigation.

Renal Impairment

Famotidine is primarily excreted by the kidneys, and accumulation occurs in patients with significant renal impairment. This can increase the risk of central nervous system side effects, particularly confusion, drowsiness, and disorientation, which are more pronounced in elderly patients. Dose intervals should be extended in those with a creatinine clearance below 50 mL/min. Regular monitoring of renal function is advisable in long-term users.

Masking of Serious Conditions

Symptom relief with famotidine should not be interpreted as ruling out serious underlying pathology. Gastric ulcers in particular can be malignant, and alarm symptoms — unintentional weight loss, dysphagia, persistent vomiting, evidence of gastrointestinal bleeding, or a palpable abdominal mass — must be investigated before or alongside treatment. Famotidine should not be used without appropriate investigation in patients over 45 years of age with new-onset dyspepsia unless the GP has determined investigation is not immediately necessary.

H. pylori and Ulcer Healing

In patients with peptic ulcers caused by Helicobacter pylori infection, acid suppression with famotidine alone is not curative. Eradication of H. pylori with antibiotic-based triple or quadruple therapy is required to prevent ulcer recurrence, and famotidine may be used adjunctively to promote mucosal healing after eradication.

Famotidine must not be used in patients who:

• Have a known hypersensitivity to famotidine, other H2 receptor antagonists, or any excipient in the formulation
• Have a history of cross-hypersensitivity to other H2 antagonists (such as cimetidine or ranitidine), as cross-reactivity may occur
• Are taking medicines that require gastric acid for absorption, where significant acid suppression would critically impair bioavailability (relative contraindication — discuss with prescriber)
• Are using famotidine OTC for more than two weeks without seeking medical review, particularly where alarm symptoms are present
• Have galactose intolerance, total lactase deficiency, or glucose-galactose malabsorption, where relevant excipients are present in the tablet formulation