cimetidine (Tagamet, Cimetex)
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Introduction
Tradename: Tagamet.
Indications
- peptic ulcer disease, dyspepsia
- gastroesophageal reflux disease (GERD), pyrosis
- erosive esophagitis
- as part of a multidrug regimen for Helicobacter pylori
- prevention of upper GI hemorrhage due to
- allergic reactions
- topical warts
- 2nd line agent for stress ulceration & stress ulcer prophylaxis
- suppression of renal tubular creatinine secretion in an enhanced creatinine clearance study to better estimate GFR
Dosage
- 300 mg IV/IM/PO every 6 hours, 400 mg PO BID or 400-800 mg PO QHS.
- continuous IV infusion 37.5 mg/hr (900 mg/day).
Tabs: 200, 300, 400, 800 mg tabs.
Liquid: 300 mg/5 mL.
Pharmacokinetics
- oral bioavailability is 60-70%
- 15-20% of drug is bound to plasma proteins
- 1/2life 1.5-2 hours Dose adjustment in patients with renal failure:
elimination via kidney
elimination via liver
protein binding = 15-20 %
elimination by hemodialysis = +/-
elimination by hemoperfusion = +
elimination by peritoneal dialysis = -
Adverse effects
- infrequent (1-10%)
- uncommon (< 1%)
- neutropenia & agranulocytosis, thrombocytopenia, bradycardia, tachycardia, hypotension, confusion, fever, diminished libido, swelling of the breasts, gynecomastia, elevated creatinine (interstitial nephritis), elevated transaminases, myalgia
- 86% anticholinergic activity of atropine[5]
Drug interactions
- coadministration of cimetidine decreases metabolism of:
- coadministration of cimetidine decreases absorption of ketoconazole
- antacids may reduce absorption of cimetidine
- many others including:
- adverse effects much more frequent in elderly with renal insufficiency
- cimetidine inhibits cyt P450 1A2, 2C9, 2D6
- may diminish levels drugs metabolized by CYP1A2, CYP2C9 & CYP2D6
Test interactions
- serum creatinine:
- cimetidine inhibits tubular secretion of creatinine
Laboratory
Mechanism of action
- competitive H2 receptor antagonist
- inhibits gastric acid secretion
- reduces pepsin output
More general terms
Additional terms
- cytochrome p450 1A2 (cytochrome P3-450, phenacetin deethylase, cytochrome p450-4, CYP1A2)
- cytochrome P450 2C9; cytochrome P450 BP-1; cytochrome P450 MP-4; S-mephenytoin-4-hydroxylase; limonene 6-monooxygenase; limonene 7-monooxygenase (CYP2C9, CYP2C10)
- cytochrome P450 2D6 (cytochrome P450 2D, cytochrome P450 DB1, debrisoquine-4-hydroxylase, CYP2D6)
References
- ↑ The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- ↑ Kaiser Permanente Northern California Regional Drug Formulary, 1998
- ↑ Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
- ↑ Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed., W.B. Saunders, 1995
- ↑ 5.0 5.1 Journal Watch 25(3):26-27, 2005 Carnahan RM, Lund BC, Perry PJ, Chrischilles EA. The concurrent use of anticholinergics and cholinesterase inhibitors: rare event or common practice? J Am Geriatr Soc. 2004 Dec;52(12):2082-7. PMID: https://www.ncbi.nlm.nih.gov/pubmed/15571547
- ↑ 6.0 6.1 Deprecated Reference
- ↑ 7.0 7.1 A Pocket Guide to the 2019 Beer's Criteria. American Geriatrics Society.