CIMETIDINE

For oral administration only. Adults The usual adult dose is 400mg twice a day with breakfast and at bedtime. Alternatively patients with duodenal or benign gastric ulceration may be treated with a single dose of 800mg at bedtime. Regimes of 200mg thrice daily with meals and 400mg at night or, if inadequate, 400mg four times daily with meals and at bedtime may also be used.

Symptomatic relief is usually rapid. Treatment should be given for 6 weeks in benign gastric ulcers, and for 8 weeks in ulcers associated with continued non-steroidal anti-inflammatory agents. The maintenance dose for patients who would benefit from reduction of gastric secretion and in patients with benign peptic ulcer disease is 400mg at bedtime.

Alternatively 400mg in the morning and at bedtime can be used. Antacids may be used concurrently if required. In oesophageal reflux 400mg four times daily with meals and at bedtime for 4 to 8 weeks is recommended to heal oesophagitis and relieve associated symptoms.

g. Zollinger-Ellison syndrome) it may be necessary to increase the dose to 400mg four times daily or occasionally higher. 4g daily may be given in divided doses. 200-400mg doses can be given every 4 to 6 hours. In the prophylaxis of acid aspiration (Mendelson’s syndrome) a single dose of 400mg may be given 90-120 minutes before induction of general anaesthesia or, in obstetric practice, at the start of labour.

4g/day. The usual precautions to avoid acid aspiration should be taken. g. following substantial resection for Crohn’s disease, the usual dosage range (as above) can be used according to individual response. In pancreatic insufficiency, for protection of pancreatic enzyme supplements, 800-1600mg/day may be given according to response, in four divided doses, one to one-and-a-half hours before meals.

Dosage should be reduced in patients with impaired renal function when creatinine clearance is below 50ml/minute. Creatinine Clearance Daily Dosage 30 - 50 ml/minute 200mg four times daily 15 - 30 ml/minute 200mg three times daily 0 - 15 ml/minute 200mg twice daily Cimetidine is removed by haemodialysis, but not to any significant extent by peritoneal dialysis.

Elderly The normal adult dose may be used in the elderly unless renal function is markedly impaired. Children In children older than one year, Cimetidine 25mg - 30mg/kg body weight per day in divided doses may be administered. Cimetidine tablets are unsuitable for children under one year old.

Adverse reactions are infrequent; diarrhoea, dizziness or rash, usually mild and transient, and tiredness have been reported. Gynaecomastia has been reported and is almost always reversible on discontinuing treatment. Biochemical or biopsy evidence of reversible liver damage has been reported occasionally.

g. those with renal failure. Thrombocytopenia and leucopenia, including agranulocytosis (see Precautions), reversible on withdrawal of treatment, have been reported rarely; pancytopenia and aplastic anaemia have been reported very rarely.

There have been very rare reports of interstitial nephritis, acute pancreatitis, fever, headache, myalgia, arthralgia, sinus bradycardia, tachycardia and heart block, all reversible on withdrawal of treatment. In common with other H2-receptor antagonists, there have been very rare reports of anaphylaxis.

Alopecia has been reported but no causal relationship has been established. Reversible impotence has also been very rarely reported but no causal relationship has been established at usual therapeutic doses. Isolated increases of plasma creatinine have been of no clinical significance.

Care should be exercised in patients with renal and hepatic impairment. Before initiation of Cimetidine therapy for any gastric ulceration, malignancy should be excluded by endoscopy, and biopsy if possible. Treatment with Cimetidine can mask symptoms and assist transient healing of gastric cancer.

The consequences of a potential delay in diagnosis should be kept in mind, particularly in patients of middle age or over, or with new or recently changed dyspeptic symptoms. Patients on prolonged Cimetidine therapy should be kept under regular surveillance with particular attention to the pathology of the gastrointestinal tract.

In patients on drug treatment or with illnesses which could cause a fall in blood cell counts, the possibility that H2 receptor antagonism could potentiate this effect should be borne in mind. Care should be taken that patients with a history of peptic ulcer, particularly the elderly, being treated with Cimetidine and a non-steroidal anti- inflammatory agent are observed regularly.

3. Contra-indications There are no known contraindications to Cimetidine, other than hypersensitivity to Cimetidine.