Verapamil Antineoplastics

Treatment for verapamil overdose includes gastric lavage, administration of activated charcoal, symptomatic and supportive cardiovascular treatment, and calcium gluconate injection. Verapamil should be used carefully with calcium salts, beta-blockers, antineoplastics, antiepileptics, antibacterials, anxiolytics, and anti-arrhythmics. 

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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