Cyclophosphamide Cimetidine

Noninterfering acetaminophen, aspirin, 5-azacytidine, baclofen, cimetidine, cyclophosphamide, cyclosporin A, famotidine, 5-duorouracil, ranitidine, verapamil... 

CYCLOPHOSPHAMIDE H2 RECEPTOR BLOCKERS-CIMETIDINE t adverse effects of alkylating agent, e.g. myelosuppression 1. Additive toxicity 2. Possible minor inhibition of cyclophosphamide metabolism via CYP2C9 Avoid co-administration of cimetidine with cyclophosphamide... 

Clinically important, potentially hazardous interactions with aluminum, aminophylline, aspirin, chlorambucil, cimetidine, clarithromycin, cyclophosphamide, cyclosporine, dicumarol, diuretics, docetaxel, estrogens, grapefruit juice, indomethacin, influenza vaccines, itraconazole, ketoconazole, lansoprazole, live vaccines, methotrexate, montelukast, omeprazole, oral contraceptives, pancuronium, phenobarbital, phenytoin, ranitidine, rifampicin, rifampin, timolol, tolbutamide, vitamin A... 

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. 

Ranitidine, and probably famotidine, appear not to increase the bone marrow toxicity of cyclophosphamide. Animal studies suggest that cimetidine might. 

Dorr RT, Soble MJ, Alberts DS. Interaction of cimetidine but not ranitidine with cyclophosphamide in mice. Cancer Res (1986) 46,1795-9. 

Lerza RA, Bogliolo GV, Mecoboni MP, Saviane AG, PannacchiUi IM. Effect of H2 antagonists cimetidine and famotidine on the hemotoxicity of cyclophosphamide. Anticancer Res... 

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