Interactions between verapamil and digoxin in Langendorff-perfused rat hearts: the role of inhibition of P-glycoprotein in the heart.

P-glycoprotein (P-gp) is expressed in tumour cells as well as normal tissues including heart. Modulation of P-gp transport in vivo may lead to increased drug penetrance to tissues with resulting increases in toxicity. We aimed to investigate the effects of P-gp on the isolated heart by digoxin infusion in the absence and presence of verapamil.