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cimetidine (Tagamet, Cimetex)

Tradename: Tagamet. Indications: 1) peptic ulcer disease, dyspepsia 2) gastroesophageal reflux disease (GERD), pyrosis 3) erosive esophagitis 4) as part of a multidrug regimen for Helicobacter pylori 5) prevention of upper GI hemorrhage due to - Zollinger-Ellison syndrome [6] 6) allergic reactions a) paclitaxel (Taxol) premedication b) urticaria 7) topical warts 8) 2nd line agent for stress ulceration & stress ulcer prophylaxis 9) 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: 1) oral bioavailability is 60-70% 2) 15-20% of drug is bound to plasma proteins 3) 1/2life 1.5-2 hours Dose adjustment in patients with renal failure: - reduce dose with eGFR < 50 mL/min [7] Adverse effects: 1) infrequent (1-10%) - headache, diarrhea, dizziness, drowsiness, nausea/vomiting constipation, skin rash 2) uncommon (< 1%) - neutropenia & agranulocytosis, thrombocytopenia, bradycardia, tachycardia, hypotension, confusion, fever, diminished libido, swelling of the breasts, gynecomastia, elevated creatinine (interstitial nephritis), elevated transaminases, myalgia 3) 86% anticholinergic activity of atropine [5] Drug interactions: 1) coadministration of cimetidine decreases metabolism of: - aminophylline, carbamazepine, carmustine, phenytoin, theophylline, tricyclic antidepressants (TCAs), warfarin 2) coadministration of cimetidine decreases absorption of ketoconazole 3) antacids may reduce absorption of cimetidine 4) many others including: - quinidine, verapamil, metoprolol, amiodarone, lidocaine, benzodiazepines, clozapine, tacrine 5) adverse effects much more frequent in elderly with renal insufficiency 6) 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: 1) specimen: a) serum, plasma (EDTA, heparin) b) collect specimen at trough concentration 2) methods: HPLC Mechanism of action: 1) competitive H2 receptor antagonist 2) inhibits gastric acid secretion 3) reduces pepsin output

Interactions

drug interactions drug adverse effects of H2-receptor antagonists

Related

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)

General

antiulcer agent H2 receptor antagonist

Properties

MISC-INFO: elimination route KIDNEY LIVER 1/2life 1.5 +/- 0.13 HOURS therapeutic-range 0.5-1.2 UG/ML toxic-range >1.3 UG/ML protein-binding 15-20% elimination by hemodialysis +/- hemoperfusion + peritoneal dialysis - pregnancy-category B safety in lactation ?

Database Correlations

PUBCHEM correlations

References

  1. The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
  2. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  3. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
  4. Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed., W.B. Saunders, 1995
  5. 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: 15571547
  6. Deprecated Reference
  7. A Pocket Guide to the 2019 Beer's Criteria. American Geriatrics Society.