The review consideration for additional "pharmacokinetic study" is safety, which mainly involves the evaluation of the effect of the volume and timetable of blood collection on subjects' health.

If the additional PG study is optional, it is important to obtain a separate consent from the subject and explain the scope of the PG study. The scope of study must be clear and can be expanded.

Sometimes clinical trials will have extension studies for those subjects who have completed the main trial to continue the study.  Because subjects enroll in a main study at different times, in reality the sponsor shall determine whether to conduct an extension study before the first subject completes the trial and therefore the extension study will be initiated before the main study ends. Usually a decision has to be made under a condition that long-term safety data is insufficient and thus, when reviewing such extension studies, it is important to pay attention to the known safety data of the drug and make reasonable assessment of the study risk and ensure the termination criteria are reasonable and adequate safety monitoring plan and periodic risk evaluation mechanism is established.

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