Abstract
The interaction in a drug combination can be assessed using either the Chou's or Jin's method. The combination index in the former (i.e., CI-C) is calculated based on doses, while the latter (i.e., CI-J) is based on effects. This perspective demonstrates a consistency between 1/CI-C and CI-J when applied to both released and simulated data. Thus, 1/CI-C and CI-J are functionally equivalent for evaluating the drug interaction. Combining these two indices is preferred: a consistency shows a reliable verdict, and an inconsistency indicates a requirement for further analyses. However, it has been observed that evaluating released data raises certain concerns.