ABSTRACT
Typically, the follow-up period (after the last dose of the drug) in a study is determined in advance. However, sometimes it is not clear how long the effect of the drug will last. In other cases, safety events that occur during the study may necessitate long duration of follow-up. Pharmacokinetics and pharmaco dynamics of the intervention may have been poorly estimated at the beginning of the study and the follow-up period may need to be changed.
