Cimetidine

Nasogastric, Oral
Prophylaxis of gastrointestinal haemorrhage from stress ulceration

Oral
Prophylaxis of acid aspiration during general anaesthesia

Oral
Gastro-oesophageal reflux disease

Oral
Hypersecretory conditions, Zollinger-Ellison syndrome

Oral
Short bowel syndrome

Oral
Benign gastric and duodenal ulceration

Oral
Pancreatic insufficiency

CrCl (mL/min)	Dosage
0-15	200 mg bid.
16-30	200 mg tid.
31-50	200 mg 4 times daily.

Should be taken with food.

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.

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

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.

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.

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.

Description:
Mechanism of Action: 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.

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.

Store between 20-25°C.

Thuốc kháng acid, chống trào ngược & chống loét

A02BA01 - cimetidine ; Belongs to the class of H2-receptor antagonists. Used in the treatment of peptic ulcer and gastro-oesophageal reflux disease (GERD).

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.