LYCOS RETRIEVER 
Cimetidine: Drugs
built 628 days ago
Cimetidine is a known inhibitor of many isozymes of the cytochrome P450 enzyme system (specifically CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4). This inhibition forms the basis of the numerous drug interactions that occur between cimetidine and other drugs. For example, cimetidine may decrease metabolism of some drugs, such as those used in hormonal contraception. Cimetidine interferes with metabolism of the hormone estrogen, enhancing estrogen activity. In women, this can lead to galactorrhea, whereas in men gynecomastia and a reduced sperm count can result
Source:
Cimetidine has been in use to treat gastric disorders since 1975. Prior to the advent of stronger anti-emetics, this drug was ... prescribed to treat the nausea associated with chemotherapy. In 1988 it was observed that colon cancer patients who had been treated with cimetidine had a significantly better response than those who had not received the drug. Many hypotheses were offered to explain this phenomenon. Since cimetidine is a histamine receptor antagonist, it was suggested that the actions were mediated by this mechanism.
Source:
Cimetidine has extensive drug interactions, particularly with antiarrhythmics (lidocaine, phenytoin, procainamide, quinidine) and may ... increase the likelihood of theophylline and cyclosporine toxicity. Because of inhibition of warfarin metabolism, cimetidine may increase INR in patients on anticoagulation therapy.
Source:
DRUG INTERACTIONS: Cimetidine may increase the blood levels of several drugs by reducing their elimination by the liver. This interaction may occur between cimetidine and warfarin (Coumadin), a commonly used blood thinning agent. Patients taking both medications should have frequent blood monitoring to avoid accumulation of high levels of warfarin leading to excessive blood thinning and bleeding. Cimetidine ... may increase the blood levels phenytoin, theophylline, lidocaine, amiodarone, metronidazole, loratadine, calcium channel blockers (e.g., diltiazem, felodipine, nifedipine), bupropion, carbamazepine and fluvastatin. Because cimetidine reduces stomach acid, it may reduce the absorption of drugs (e.g., ketoconazole) that are best absorbed in acidic conditions. Such drugs should be administered at least 2 hours before the administration of cimetidine.
Source:
HEMATOLOGIC: Decreased white blood cell counts in Cimetidine-treated patients (approximately 1 per 100,000 patients), including agranulocytosis (approximately 3 per million patients), have been reported, including a few reports of recurrence on rechallenge. Most of these reports were in patients who had serious concomitant illnesses and received drugs and/or treatment known to produce neutropenia. Thrombocytopenia (approximately 3 per million patients) and, very rarely, cases of pancytopenia or aplastic anemia have ... been reported. As with some other H2-receptor antagonists, there have been extremely rare reports of immune hemolytic anemia.
Source:
Cimetidine, a H-2 type anti-histamine, has been used to treat horses with melanoma with controversial results. Although better results have been reported in mouse models, and there are some indications of efficacy in humans with melanoma, cimetidine is generally considered to be palliative in cancer treatment. Responses to xenobiotic drugs often are not predictable from one species to the next due to species differences in drug metabolizing enzymes. However, it is encouraging so far that extrapolation of therapeutic responses between species does not appear to be a problem with low concentrations of the vitaletheine modulators, a result that would be expected if the vitaletheine modulators are constitutive in normal mammalian tissues.
Source:
MORE ABOUT
Drugs