Fluorouracil Cimetidine

CIMETIDINE FLUOROURACIL Altered efficacy of fluorouracil Inhibition of metabolism and altered action Monitor more closely. May be of clinical benefit. No additional toxicity was noted in one study... 

Chloral hydrate Chloramphenicol Cimetidine Ciprofloxacin Clofibrate Danazol Disulfiram Doxycycline Erythromycin Fenofibrate Fluconazole Fluorouracil Fluoxetine Fluvoxamine Gemfibrozil Influenza vaccine Isoniazid Itraconazole Fovastatin Metronidazole Miconazole Moxalactam Neomycin Norfloxacin Ofloxacin Omeprazole Phenylbutazone Piroxicam Propafenone Propoyxphene Quinidine Sertraline Sulfamethoxazole Sulfinpyrazone Tamoxifen Testosterone Vitamin E Zafirlukast... 

Interferes w/ DNA synth Dose Adults. Anaerobic Infxns 500 mg IV q6-8h Amebic dysentery 750 mg/d PO for 5-10 d Trichomoniasis 250 mg PO tid for 7 d or 2 g PO X 1 C. difficile 500 mg PO or IV qSh for 7-10 d (PO preferred IV only if pt NPO) Vaginosis 1 applicator-full intravag bid or 500 mg PO bid for 7 d Acne rosacea/skin Apply bid Peds. 30 mg/ kg PO/IV/d q6H, 4 g/d max-s-. Amebic dysentery 35-50 mg/kg/24 h PO in 3 -s- doses for 5-10 d Rx 7-10 d for C. difficile-, in hepatic impair Caution [B, M] Avoid EtOH Contra 1st tri of PRO Disp Tabs, caps, IV, topical lotion, intravag gel, cream SE Disulfiram-like Rxn dizziness, HA, GI upset, anorexia, urine discoloration Interactions t Effects W/ cimetidine T effects OF carbamazepine, fluorouracil, Li, warfarin -1- effects W/ barbiturates, cholestyramine, colestipol, phenytoin EMS t Effects of anticoagulants concurrent EtOH use can cause disulfiram-like Rxn (tach, N/V, sweating, flushing, headache, blurred vision, confusion) may cause a metallic taste and discolored urine OD May cause N/V/D, numbness in hands and feet, Szs, and loss of coordination symptomatic and supportive... 

Harvey VJ, Slevin ML, Dilloway MR, Clark PI, Johnston A, Lant AF. The influence of cimetidine on the pharmacokinetics of 5-fluorouracil. Br J Clin Pharmacol 1984 18(3) 421-30. 

Komatsubara M, Nagata T, Miyauchi S, Kamo N. Cimetidine enhances the antiproliferative effect of 5-fluorouracil on colon carcinoma SW620. Anticancer Res 1999 19(2A) 1153-7. 

Pre-treatment for 4 weeks with cimetidine 1 g/day increased the oral systemic availability of fluorouracil by 74% the AUC was increased by 27% and total body clearance was reduced by 28% (142). 

In a study in 8 patients, cimetidine 400 mg twice daily increased the AUC of epirubicin by 50%. At the same time the AUCs of two metabolites of epirubicin, epirubicinol and 7-deoxydoxorubicinol aglycone, increased by 41% and 357%, respectively. Liver blood flow also increased by 17%. The mechanism is unknown. More study of this interaction is needed but be aware of the possibility of cimetidine inereasing the exposure to epirubicin monitor the patient closely and adjust epirubicin dosage if needed. Cimetidine is available without a preseription in some countries so that patients may unwittingly increase the toxicity of epirubicin. Cimetidine has also increased the levels or toxicity of some other antineoplastics, see Nitrosoureas + Cimetidine , p.655, Cyclophosphamide + H2-receptor antagonists , p.626 and Fluorouracil + H2-reeeptor antagonists , p.633. 

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