Brand names of Cimetidine in Kenya
Cemet®, Cosmos Ltd
Labcimet®,Lab and Allied
Medicit® , Medisel
Tagamet®, GSK
Ulcidin®,West Coast
Ulmet® , Universal Corporation Limited
Mechanism of Action:
Cimetidine is a histamine H2-antagonist and inhibits actions of histamine mediated by H2-receptors such as gastric acid secretion and pepsin output.
INDICATIONS
Cimetidine is indicated for the following.
a) The treatment of duodenal and benign gastric ulceration, and oesophageal reflux disease.
b) The treatment of persistent dyspeptic symptoms with or without ulceration, particularly meal-related upper abdominal pain.
c) The prophylaxis of gastro-intestinal haemorrhage from stress ulceration in seriously ill patients.
d) Before general anaesthesia in patients thought to be at risk of acid aspiration (Mendelson’s) syndrome, particularly obstetric patients during labour.
e) To reduce malabsorption and fluid loss in short bowel syndrome.
f) To reduce degradation of enzyme supplements in pancreatic insufficiency.
g) In the management of Zollinger-Ellison syndrome.
DOSAGE AND ADMINISTRATION:
The total daily dose should not normally exceed 2.4g. Dosage should be reduced in patients with impaired renal function.
Adults: the usual dosage is 400mg twice a day with breakfast and at bedtime. For patients with duodenal or benign gastric ulceration, a single daily dose of 800mg at bedtime is recommended. Other effective regimens are 200mg, 3 times a day with meals and 400mg at bedtime (1g/day) and, if inadequate, 400mg, 4 times a day (1.6g/day), also with meals and at bedtime. Symptomatic relief is usually rapid.
Treatment should be given initially for at least 4 weeks (6 weeks in benign gastric ulcer). Most ulcers will have healed by that stage, but those which have not will usually do so after a further course of treatment. Treatment may be continued for longer periods in those patients who may benefit from reduction of gastric secretion and the dosage may be reduced, as appropriate, to 400mg at bedtime or 400mg in the morning and at bedtime. In patients with benign peptic ulcer disease, relapse may be prevented by continued treatment, usually with 400mg at bedtime; 400mg in the morning and at bedtime has also been used.
In oesophageal reflux disease, 400mg, 4 times a day, with meals and at bedtime, for 4 to 8 weeks is recommended to heal oesophagitis and relieve associated symptoms. In patients with very high gastric acid secretion (e.g. Zollinger-Ellison syndrome) it may be necessary to increase the dose to 400mg, 4 times a day, or in occasional cases further. Antacids can be made available to all patients until symptoms disappear.
In the prophylaxis of haemorrhage from stress ulceration in seriously ill patients, doses of 200mg-400mg can be given every 4 to 6 hours. In patients thought to be at risk of acid aspiration syndrome an oral dose of 400mg can be given 90-120 minutes before induction of general anaesthesia or, in obstetric practice, at the start of labour. While such a risk persists, a dose of up to 400mg may be repeated at 4 hourly intervals, as required, up to the usual daily maximum of 2.4g. The usual precautions to avoid acid aspiration should be taken. In short bowel syndrome, e.g. following substantial resection for Crohn’s disease, the usual dosage range can be used according to individual response.
To reduce degradation of pancreatic enzyme supplements, 800mg-1,600mg a day may be given according to response in 4 divided doses, 1 to 1½ hours before meals.
Elderly: the normal adult dosage may be used unless renal function is markedly impaired.
Children: experience in children is less than that in adults. In children more than one year old, cimetidine 25mg-30mg/kg body weight per day in divided doses may be administered. The use of cimetidine in infants under one year old has not yet been fully evaluated; 20mg/kg body weight per day in divided doses has been used.
Patients with impaired renal function: dosage should be reduced in patients with impaired renal function according to creatinine clearance. The following dosages are suggested:
| Creatinine clearance 0 to 15ml per minute 15ml to 30ml per minute 30ml to 50ml per minute over 50ml per minute | Cimetidine dosage 200mg, twice a day 200mg, 3 times a day 200mg, 4 times a day normal dosage. |
CONTRAINDICATIONS
Hypersensitivity to Cimetidine or to any expients
DRUG INTERACTIONS
Cimetidine can prolong the elimination of drugs metabolised by oxidation in the liver.
Although pharmacological interactions between cimetidine and a number of drugs have been demonstrated, eg diazepam and propranolol, only those with oral anticoagulants, phenytoin and theophylline and intravenous lignocaine appear, to date, to be of clinical significance. Close monitoring of patients on cimetidine receiving oral anticoagulants or phenytoin is recommended and a reduction in the dosage of these drugs may be necessary.
In patients on drug treatment or with illnesses that could cause falls in blood cell count, the possibility that H2-receptor antagonism could potentiate this effect should be borne in mind.
Cimetidine has the potential to affect the absorption, metabolism or renal excretion of other drugs which is particularly important when drugs with a narrow therapeutic index are administered concurrently. The altered pharmacokinetics may necessitate dosage adjustment of the affected drug or discontinuation of treatment .
Interactions may occur by several mechanisms including:
1) Inhibition of certain cytochrome P450 enzymes (including CYP1A2, CYP2C9, CYP2D6 and CYP3A3/A4, and CYP2C18); Inhibition of these enzymes may result in increased plasma levels of certain drugs including warfarin-type coumarin anticoagulants (e.g. warfarin), tricyclic antidepressants (e.g. amitriptyline), class I antiarrhythmics (e.g. lidocaine), calcium channel blockers (e.g. nifedipine, diltiazem), oral sulfonylureas (e.g. glipizide), phenytoin, theophylline and metoprolol.
2) Competition for renal tubular secretion; This may result in increased plasma levels of certain drugs including procainamide, metformin, ciclosporin and tacrolimus.
3) Alteration of gastric pH; The bioavailability of certain drugs may be affected. This can result in either an increase in absorption (e.g. atazanavir) or a decrease in absorption (e.g. some azole antifungals such as ketoconazole, itraconazole or posaconazole).
4) Unknown mechanisms; Cimetidine may potentiate the myelosuppressive effects (e.g. neutropenia, agranulocytosis) of chemotherapeutic agents such as carmustine, fluorouracil, epirubicin, or therapies such as radiation. Isolated cases of clinically relevant interactions have been documented with narcotic analgesics (e.g. morphine).
ADVERSE EFFECTS
Blood and Lymphatic system disorders:
Uncommon: Leukopenia
Rare: Thrombocytopenia, aplastic anaemia
Very rare: Pancytopenia, agranulocytosis
Immune system disorders:
Very rare: Anaphylaxis. Anaphylaxis is usually cleared on withdrawal of the drug.
Psychiatric disorders
Uncommon: Depression, confusional states, hallucinations. Confusional states, reversible within a few days of withdrawing cimetidine, have been reported, usually in elderly or ill patients.
Nervous system disorders
Common: Headache, dizziness
Cardiac disorders
Uncommon: Tachycardia
Rare: Sinus bradycardia
Very rare: Heart block
Gastrointestinal disorders
Common: Diarrhoea
Very rare: Pancreatitis. Pancreatitis cleared on withdrawal of the drug.
Hepatobiliary disorders
Uncommon: Hepatitis
Rare: Increased serum transaminase levels. Hepatitis and increased serum transaminase levels cleared on withdrawal of the drug.
Skin and subcutaneous tissue disorders
Common: Skin rashes
Very rare: Reversible alopecia and hypersensitivity vasculitis. Hypersensitivity vasculitis usually cleared on withdrawal of the drug.
Musculoskeletal and connective tissue disorders
Common: Myalgia
Very rare: Arthralgia
Renal and urinary disorders
Uncommon: Increases in plasma creatinine
Rare: Interstitial nephritis. Interstitial nephritis cleared on withdrawal of the drug. Small increases in plasma creatinine have been reported, unassociated with changes in glomerular filtration rate. The increases do not progress with continued therapy and disappear at the end of therapy.
Reproductive system and breast disorders
Uncommon: Gynaecomastia and reversible impotence. Gynaecomastia is usually reversible upon discontinuation of cimetidine therapy. Reversible impotence has been reported particularly in patients receiving high doses (e.g. in Zollinger-Ellison Syndrome). However, at regular dosage, the incidence is similar to that in the general population.
Very rare: Galactorrhoea
General disorders and administration site conditions
Common: Tiredness
Very rare: Fever. Fever cleared on withdrawal of the drug.
Clinical | Pharmacokinetic data
Pregnancy Category:
Routes of Administration:
Bioavailability:
Protein Binding:
Metabolosim:
Onset of Action:
Elimination Half life:
Excretion:
Legal Status | Dosage forms & Strengths
Prescription Category:
Narcotic Drugs and Psychotropic Substances (Control ) Act Schedule:
Dosage Forms | Strengths:
Drug Indentifiers:
Drug Images
References/ Citation:
Cimetidine