Cimetidine

Intravenous
Benign gastric and duodenal ulceration, Zollinger-Ellison syndrome

Oral
Prophylaxis of gastrointestinal haemorrhage from stress ulceration

Oral
Benign gastric and duodenal ulceration

Oral
Pancreatic insufficiency

Oral
Non-ulcer dyspepsia

Oral
Zollinger-Ellison syndrome

Oral
Gastro-oesophageal reflux disease

Oral
Prophylaxis of acid aspiration during general anaesthesia

Oral
Short bowel syndrome

Oral:

CrCl	Dosage
0-15	200 mg bid.
16-30	200 mg tid.
31-50	200 mg 4 times daily.

Intravenous:
Severe: 300 mg 12 hrly.

Should be taken with food.

Cimetidine 300 mg should be diluted to a total of 20 mL (IV inj) and at least 50 mL (intermittent IV infusion) w/ either NaCl 0.9% inj, glucose 5% or 10%, or lactated Ringer's soln.

History of peptic ulcer. Increased risk of developing community-acquired pneumonia in the elderly, patients w/ chronic lung disease, DM, or the immunocompromised. Increased possibility of a hyperinfection caused by Strongyloides stercoralis in immunocompromised patients. Possibility of malignancy should be excluded prior to therapy as the drug may mask symptoms and delay diagnosis of gastric malignancy. Avoid rapid IV inj. Renal and hepatic impairment. Pregnancy and lactation.

Diarrhoea, other GI disturbances, dizziness, headache, tiredness, myalgia, arthralgia, rashes, altered LFTs, reversible confusional states. Rarely, hypersensitivity reactions and fever, reversible alopecia, blood disorders (e.g. agranulocytosis, leucopenia, and thrombocytopenia), acute pancreatitis, interstitial nephritis, hallucinations and depression, CV disorders (e.g. bradycardia, tachycardia, heart block), transient hypotension, gynaecomastia and impotence.
Potentially Fatal: Rarely, hepatotoxicity, cardiac arrest and arrhythmias due to rapid IV inj.

IV/Parenteral/PO: B

May impair ability to drive, operate machinery and perform hazardous tasks requiring mental alertness.

Monitor CBC, gastric pH, occult blood w/ GI bleeding and renal function.

Symptoms: Dizziness, bradycardia, CNS depression, vomiting. Management: Induce vomiting and/or gastric lavage, followed by symptomatic and supportive treatment.

Reduces absorption of dasatinib, ketoconazole, itraconazole and posaconazole. May increase serum levels of phenytoin, theophylline, lidocaine, hydroxyzine and oral anticoagulants. Absorption may be reduced by antacids. Decreased bioavailability w/ metoclopramide, sucralfate or propantheline. May potentiate the myelosuppressive effects (e.g. agranulocytosis, neutropenia) of myelosuppressive drugs (e.g. antimetabolites, alkylating agents) or therapies (e.g. radiation).

Food delays the rate and slightly decreases extent of absorption. May enhance gastric mucosal irritation w/ alcohol.

Description: Cimetidine competitively inhibits histamine at H₂-receptors of the gastric parietal cells resulting in decreased gastric acid secretion, gastric volume and hydrogen ion concentration. It is also used in patients w/ pancreatic insufficiency to reduce the breakdown of pancreatic enzyme supplements.
Onset: 1 hr.
Duration: 4-5 hr.
Pharmacokinetics:
Absorption: Readily absorbed from the GI tract. Food delays the rate and slightly decreases extent of absorption. Bioavailability: Approx 60-70%. Time to peak plasma concentration: Approx 1-3 hr.
Distribution: Widely distributed; enters breast milk, crosses the placental barrier. Volume of distribution: Approx 1 L/kg. Plasma protein binding: Approx 20%.
Metabolism: Partially hepatic, converted to sulfoxide and hydroxymethylcimetidine.
Excretion: Via urine (oral: approx 50%, IV: 75%) as unchanged drug. Elimination half-life: Approx 2 hr.

Store between 16-30°C. Protect from light.

Antacids, Antireflux Agents & Antiulcerants

Anon. Cimetidine. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 16/01/2014.

Buckingham R (ed). Cimetidine. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 16/01/2014.

Cimetidine Inj (Hosipra, Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 16/01/2014.

McEvoy GK, Snow EK, Miller J et al (eds). Cimetidine. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 16/01/2014.