Cimetidine


Generic Medicine Info
Indications and Dosage
Nasogastric, Oral
Prophylaxis of gastrointestinal haemorrhage from stress ulceration
Adult: In critically ill patients: 200-400 mg 4-6 hourly via the oral or nasogastric route.

Oral
Prophylaxis of acid aspiration during general anaesthesia
Adult: As tab: 400 mg given 90-120 minutes before induction of anaesthesia. In obstetric patients: 400 mg at the start of labour, may increase dose up to 400 mg 4 hourly if necessary. Max: 2,400 mg daily.

Oral
Gastro-oesophageal reflux disease
Adult: 400 mg 4 times daily or 800 mg bid for 4-12 weeks.

Oral
Hypersecretory conditions, Zollinger-Ellison syndrome
Adult: 300 or 400 mg 4 times daily, may increase dose if necessary. Max: 2,400 mg daily. Doses are individualised according to patient's needs.

Oral
Short bowel syndrome
Adult: Initially, 400 mg bid, adjust dose according to response.

Oral
Benign gastric and duodenal ulceration
Adult: 800 mg daily at bedtime or 400 mg bid for 4 weeks for duodenal ulcer, 6 weeks for gastric ulcer, and 8 weeks for NSAID-associated ulcer; may increase dose to 400 mg 4 times daily as necessary. Maintenance: 400 mg daily at bedtime or bid. Dosage recommendation may vary among countries or individual products. Refer to specific product guidelines.

Oral
Pancreatic insufficiency
Adult: 800-1,600 mg daily in 4 divided doses, 60-90 minutes before meals.
Renal Impairment
CrCl (mL/min) Dosage
0-15 200 mg bid.
16-30 200 mg tid.
31-50 200 mg 4 times daily.
Administration
Should be taken with food.
Special Precautions
Patient with immunocompromised states, history of peptic ulcer. Possibility of gastric malignancy should be excluded prior to therapy. Do not use the syrup for the prophylaxis of acid aspiration. Renal and hepatic impairment. Elderly. Pregnancy and lactation.
Adverse Reactions
Significant: Vitamin B12 deficiency (prolonged use). Rarely, confusion; strongyloidiasis hyperinfection (immunocompromised patient).
Gastrointestinal disorders: Diarrhoea.
General disorders and administration site conditions: Fatigue.
Musculoskeletal and connective tissue disorders: Myalgia.
Nervous system disorders: Headache, dizziness, drowsiness.
Reproductive system and breast disorders: Gynaecomastia.
Skin and subcutaneous tissue disorders: Rashes.
IV/Parenteral/PO: B
Monitoring Parameters
Monitor gastric pH, CBC, renal function (to adjust dose), occult blood with GI bleeding; prothrombin time (in concomitant use with anticoagulants). Assess for signs of confusion.
Overdosage
Symptoms: CNS symptoms (e.g. unresponsiveness). Management: Supportive and symptomatic therapy. Administer activated charcoal if ingestion is within 1 hour. Induce vomiting or perform gastric lavage.
Drug Interactions
May inhibit certain CYP450 enzymes and increase the plasma concentration of warfarin-type coumarin anticoagulants (e.g. warfarin), TCAs (e.g. amitriptyline), class I antiarrhythmics (e.g. lidocaine), Ca channel blockers (e.g. nifedipine, diltiazem), oral sulfonylureas (e.g. glipizide), phenytoin, theophylline, metoprolol. Increased plasma concentration of procainamide, metformin, ciclosporin, and tacrolimus. Increased absorption of atazanavir. Decreased absorption of ketoconazole, itraconazole, posaconazole. May enhance the myelosuppressive effect of carmustine, fluorouracil, epirubicin.
Action
Description: Cimetidine competitively inhibits histamine at the H2 receptor of the gastric parietal cells, thereby causing a decrease in gastric acid secretion, gastric volume and hydrogen ion concentration.
Onset: 1 hour.
Duration: 4-5 hours (80% reduction in gastric acid secretion after a 300 mg dose).
Pharmacokinetics:
Absorption: Rapidly absorbed from the gastrointestinal tract. Food delays the rate and slightly decreases extent of absorption. Bioavailability: Approx 60-70%. Time to peak plasma concentration: 1-2 hours.
Distribution: Widely distributed. Crosses the placenta and enters breast milk. Volume of distribution: 1-1.5 L/kg. Plasma protein binding: Approx 20%.
Metabolism: Partially metabolised in the liver to sulfoxide and hydroxymethylcimetidine.
Excretion: Via urine (oral: approx 50%, IV: 75%) as unchanged drug; faeces. Elimination half-life: Approx 2 hours.
Chemical Structure

Chemical Structure Image
Cimetidine

Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 2756, Cimetidine. https://pubchem.ncbi.nlm.nih.gov/compound/Cimetidine. Accessed May 26, 2021.

Storage
Store between 20-25°C.
MIMS Class
Antacids, Antireflux Agents & Antiulcerants
ATC Classification
A02BA01 - cimetidine ; Belongs to the class of H2-receptor antagonists. Used in the treatment of peptic ulcer and gastro-oesophageal reflux disease (GERD).
References
Anon. Cimetidine. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 30/04/2021.

Anon. Cimetidine. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 30/04/2021.

Buckingham R (ed). Cimetidine. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 30/04/2021.

Cimetidine Solution (Pharmaceutical Associates, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 30/04/2021.

Cimetidine Tablet, Film Coated (Mylan Pharmaceuticals Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 04/05/2021.

Joint Formulary Committee. Cimetidine. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 30/04/2021.

Tagamet 200 mg Tablets (Chemidex Pharma Limited). MHRA. https://products.mhra.gov.uk. Accessed 30/04/2021.

Tagamet 400 mg Tablets (Chemidex Pharma Limited). MHRA. https://products.mhra.gov.uk. Accessed 30/04/2021.

Tagamet 800 mg Tablets (Chemidex Pharma Limited). MHRA. https://products.mhra.gov.uk. Accessed 30/04/2021.

Tagamet Syrup 200 mg/5 mL (Essential Pharma). MHRA. https://products.mhra.gov.uk. Accessed 30/04/2021.

Disclaimer: This information is independently developed by MIMS based on Cimetidine from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2021 MIMS. All rights reserved. Powered by MIMS.com
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