Vincristine Nifedipine

Clinically important, potentially hazardous interactions with abacavir, atorvastatin, bepridil, bupropion, carbamazepine, clarithromycin, cyclosporine, dexamethasone, digoxin, felodipine, fluticasone propionate, fosamprenavir, itraconazole, ketoconazole, lovastatin, methadone, midazolam, nicardipine, nifedipine, phenobarbital, phenytoin, rifabutin, simvastatin, sirolimus, St John s wort, systemic lidocaine, tacrolimus, tenofovir, trazodone, vinblastine, vincristine, voriconazole, warfarin, zidovudine... 

Vincristine Nifedipine Increase in AUC (3.4-fold) P-gp, CYP3A4 Fedeli et al. (1989)... 

Fedeli L, Colozza M, Boschetti E, Sabalich I, Aristei C, Guerdolini R, Del Favero A, Rossetti R, Tonato M, Rambotti P, Davis S. Pharmacokinetics of vincristine in cancer patients treated with nifedipine. Cancer 1989 64 1805-1811. 

The efficacy of doxorubicin can be increased by verapamil and nicardipine in doxorubicin-resistant tissue culture systems, while nifedipine has only minimal activity. A study in five patients with small cell lung cancer given doxorubicin, vincristine, etoposide and cyclophosphamide showed that when they were given verapamil 240 to 480 mg daily the AUC of doxorubicin was doubled, its peak serum levels were raised and its clearance was reduced. No increased toxicity was seen in this study. However, although another study found no increase in non-cardiac toxic-ities, verapamil caused an unacceptable degree of cardiac toxicity. Be alert for this possibility if both drugs are used. 

A study in 9 patients with a variety of malignant diseases found that treatment with antineoplastics reduced the absorption of a single 160-mg oral dose of verapamil. The verapamil AUC in 8 patients was reduced by 40% (range 7 to 58%), and one patient conversely had a 26% increase. Five patients reeeived a modified COPP regimen (cyclophosphamide, vincristine, procarbazine, prednisone) and four received VAC (vindesine, doxornbicin, cisplatin). It is believed that these antineoplastics damage the lining of the upper part of the small intestine, which impairs the absorption of verapamil. The clinical relevance of this reduction does not appear to have been studied. Note that verapamil may affect levels of anthracyclines , (p.611), etoposide , (p.631), and possibly docetaxel , (p.662). In addition, nifedipine may affect the levels of vincristine , (p.671). 

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