Trypsin and cell culture
It would be stressful for cells to be trypsinized 24 hours after seeding. After cells are plated, there is a lag time to start growing. Perhaps, during the lag time, physiological state of cells is stabilized. They have to express proteins digested by trypsin and display on the surface etc. Then you could disturb the state again by trypsinizing cells again if you replate cells after 24 hours. 
I would not deny some cells are not affected by trypsin much, but you should be carful. 


  if I can treat them with drug the same day I add trypsin for counting.


It is not preferable, but in some cases, such a way is taken actually. If you could, you might want to give us more information about which cells and drugs you are going to use.

PS

If you trypsinize cells to count and do not replate them, you do not need to worry about the cell condition, as WYSIWYG says.