First, evaluate what drugs are prohibited for concomitant use, in particular, those drugs that are prohibited due to safety concern. For example, If concomitant medication may lead to serious drug drug interactions (e.g. the effect of the special metabolic enzyme CYP3A4), special measures need to be prepared to protect the subject's safety.

Second, pay attention to those concomitant drugs that may affect efficacy assessment. For example, similar pharmacological mechanisms or drug that cause similar efficacy shall be prohibited to prevent interfering with interpretation of the efficacy of the study drug. Meanwhile, the rights of subjects to receive appropriate treatment should also be considered. If conflicts are found, the priority is to protect the rights of subjects. In addition, pre-medication may be given to reduce adverse reactions for certain drugs. For example, anti-histamine and corticosteroid, and it is necessary to evaluate the necessity of pre-medication.

(中文版)