Almost all trial combine recruitment and treatment at the same...

Almost all trial combine recruitment and treatment at the same time (well recruitment followed soon by treatment). About the only trial type that doesn’t do this is Phase 1 healthly volunteer studies where it is relatively common to recruit say 20 patients and then treat them all at once. This can go wrong occasionally if the drug turns out to be much more active or have some weird side-effect. Now days you are supposed to dose and then wait a couple of hours before treating the next patient rather than just line them all up and dose at once.