Moreover, a significantly higher dosage is usually needed to serve as a good P-gp inhibitor for these drugs, which can lead to unexpected side effects.[10,11] On the other hand, compounds inhibiting ATP hydrolysis may serve as better inhibitors since ATP binding and hydrolysis has been found to be essential for P-gp function, where one molecule of drug is effluxed at the expense of two molecules of ATP.[4] These drugs are unlikely to be transported by P-gp and a lower dose is required to achieve favorable P-gp inhibition, especially when used locally at gut lumen and cancer.[12]. This evidence concerns the gene PGP and cancer.