How does Apo-Cimetidine (Cimetidine) work:

Apo-Cimetidine (Cimetidine) is a histamine H2-receptor antagonist which competitively inhibits the action of histamine on the H2-receptors of parietal cells.

Apo-Cimetidine is uesd in prevention of the recurrence of duodenal or stress ulcer in patients at risk of haemorrhage, the management of pathological hypersecretion. It is also used to reduce the gastric acidity and secretory volume thus reducing the risk of pulmonary damage from aspiration of gastric contents in patients undergoing general anaesthesia. Apo-Cimetidine can be used in conjunction with a H1 antagonist for the prevention of anaphylactic reaction secondary to histamine release caused by infusion of certain medicines e.g. radioopaque contrast agents and plasma substitutes.

Dosage & Administration:

Adults:

Duodenal, Peptic and Benign Gastric Ulcer - The usual dose is 800mg at night. Reduction of nocturnal gastric acid secretion appears to be the most important factor in healing duodenal ulcers. Alternatively, 400mg may be given twice daily, in the morning and at bedtime.

Reflux oesophagitis - The usual dose is 400mg twice daily or 800mg once daily with the evening meal. More severe cases may require up to 1.6g per day given in 4 divided doses. Apo-Cimetidine should be given at mealtimes and at bedtime for up to 12 weeks.

Dyspepsia - 800mg a day in divided doses for 4 to 6 weeks. For the short term treatment of pain associated with hyper-acidity or dyspepsia 200mg taken as required up to a maximum of 800mg per day.

Zollinger-Ellison Syndrome and other hypersecretory conditions - Doses need to be individualised and are given in divided doses, with meals and at bedtime. In recent studies median doses of 3-5g daily were required and in patients with gastronoma doses of up to a maximum of 12g daily have been used for more than a year.

Children:

For children aged 1 - 12 years: 20 to 25mg/kg/day in divided doses every 4 to 6 hours.

Less than 1 year: 20mg/kg/day in divided doses every 4 to 6 hours.

Neonates: 10-15mg/kg/day in divided doses every 4 to 6 hours.

Elderly:

If renal and hepatic function is good, dosage reduction may not be necessary. However, most elderly patients show some decrease in the clearance of cimetidine and doses may need to be decreased by 30-50%.

Side Effects:

• headache
• diarrhoea
• tiredness
• dizziness
• drowsiness
• skin rashes
• constipation
• alopecia
• agitation
• psychosis
• depression
• anxiety
• disorientation
• thrombocytopenia
• leucopenia
• neutropenia
• pancytopenia
• allergic reactions
• arthralgia
• myalgia
• interstitial nephritis
• hepatotoxicity
• pancreatitis
• hepatitis
• fever
• interstitial nephritis
• increases in plasma creatinine
• tachycardia
• sinus bradycardia
• anaphylaxis

Precautions:

Caution is required in patients with impaired kidney and liver function. Apo-Cimetidine levels are reduced by haemodialysis, but are unchanged by peritoneal dialysis. Therefore Apo-Cimetidine should be administered after a patient has undergone haemodialysis. Treatment of gastric ulcers with cimetidine can mask the symptoms associated with carcinoma of the stomach and diagnosis of the condition may be delayed. The delay in diagnosis should by borne in mind in middle aged or older patients with new or recently changed dyspeptic symptoms. If a gastric ulcer is suspected the possibility of malignancy should be eliminated before treatment with Apo-Cimetidine begins.