Description of Cimetidine
Cimetidine is a drug in the class of histamine H2 receptor antagonist. Inhibition of H2 receptor by Cimetidine in the stomach reduces gastric acid secretion. This action is what makes it useful in medical world. It comes in different dosage forms which include tablets, injections or injectable solution and oral solution. It also comes in different strengths and this include:
- Injection: 150 mg/ml, 200 mg/2ml, 300 mg/2ml
- Tablets: 200 mg, 300 mg, 400 mg, 600 mg, 800 mg
- Oral Solution: 300 mg/5ml
Pharmacological Action of Cimetidine
Cimetidine is a selective dose-dependent reversible histamine H2- receptor antagonist. Its main action is to inhibit gastric acid secretion. It also inhibits competitively the other actions of histamine mediated by H2 -receptors. The decrease in gastric acid secretion occurs regardless of the nature of the physiological stimulus to secretion, i.e, basal (fasting) and nocturnal acid secretion, in reduced. Both the volume of secretion and the concentration of acid and pepsin in the secretion are reduced. It also inhibits gastric secretion elicited by muscarinic agonists or by gastrin.
Uses and Indications of Cimetidine
- Cimetidine is used in the treatment of gastric and duodenal ulcers, oesophageal reflux, Zollinger-Ellison syndrome and in other conditions associated with gastric hypersecretory states.
- It is also indicated in the management of those patients who are at high risk from haemorrhage of the upper gastro-intestinal tract due to hepatic failure and treatment with immuno suppressive agents, following kidney transplant.
Contraindications of Cimetidine
- Hypersensitivity to cimetidine.
- The safety in pregnancy and lactation has not been established.
Before giving Cimetidine to patients with gastric ulcers, the possibility of malignancy should be excluded since Cimetidine may mask symptoms and delay diagnosis.
Dosage and Directions for Use
- Cimetidine may be given by the intravenous or intramuscular routes; the total daily dose by any route should not normally exceed 2.4 g in a day.
- The usual dose of Cimetidine by intravenous injection is 200 mg, which should be given slowly over at least 2 minutes and may be repeated every 4 to 6 hours.
- If a larger dose is required, or if the patient has cardiovascular impairment, intravenous infusion is recommended.
- For an intermittent intravenous infusion, the recommended dose is 400 mg (in 100 mL of sodium chloride 0,9%), given over 30 minutes to 1 hour and repeated every 4 to 6 hours if necessary.
- For a continuous intravenous infusion, the recommended rate is 50 mg to 100 mg per hour.
- The usual intramuscular dose is 200 mg which may be repeated at intervals of 4 to 6 hours.
The dosage of cimetidine should be reduced in patients with impaired renal function; suggested doses according to creatinine clearance are:
- creatinine clearance of 0 to 15 mL per minute, 200 mg twice daily
- creatinine clearance of 15mL to 30 mL per minute, 200 mg three times daily
- creatinine clearance of 30 mL to 50 mL per minute, 200 mg four times daily
- creatinine clearance of over 50 mL per minute, normal dosage.
Clinical experience in children is limited. Therefore, Cimetidine therapy cannot be recommended in children unless in the judgement of the physician, anticipated benefits outweigh the potential risk. In limited experience, 20 to 40 mg/kg per day has been administered in divided doses orally or parenterally. There is no evidence of clinical use in babies and Cimetidine should therefore not be given to infants under one year of age.
Side Effects of Cimetidine
- The most common side-effects reported have been diarrhoea, dizziness, tiredness, headache and rashes.
- Reversible confusional states, especially in the elderly or in seriously ill patients such as those with renal failure, have occasionally occurred.
- Cimetidine has a weak anti-androgenic effect and gynaecomastia and impotence have also occasionally occurred in men, receiving relatively high doses for conditions such as the Zollinger-Ellison syndrome.
Other adverse effects which have been reported are:
- Hypersensitivity reactions and fever,
- Arthralgia and myalgia,
- Blood disorders including agranulocytosis or neutropenia and thrombocytopenia,
- Interstitial nephritis
- Cardiovascular disorders.
Intravenous injections of cimetidine should be given slowly and intravenous infusion is recommended in patients with cardiovascular impairment.
Precautions to Observe While Using Cimetidine
- It should be given in reduced dosage to patients with impaired renal function.
- Cimetidine crosses the placental barrier and is excreted into breast milk.
- Reduction in the dosage of some agents, such as cyclosporin, lignocaine, nifedipine, phenytoin, suxamethonium, theophylline and warfarin may be needed.
Cimetidine Overdose and it’s Treatment
Treatment of Cimetidine Overdose is supportive and symptomatic. Dialysis may be necessary in cases where renal failure is present.
How to Store Cimetidine
Store in cool & dry place below 30°C. Protect from light. Keep out of the reach of children.