what do you mean by “targeted drug delivery system”

Question: what do you mean by "targeted drug delivery system"
- Keywords:
  targeted drug delivery system
Asked by Ben.m to Sam on 13 Jun 2016.
- Sam Briggs answered on 13 Jun 2016:
  
  Hi Ben.M,
  
  So most drugs are released into the body and ride through the arterial system being transported into all cells. Now most anti-cancer drugs are designed just to kill cells, the idea behind chemotherapy is that you kill the tumour before it kills you. However, if you could target, or confine the drugs to just the I’ll part of the body, or only be released near tumours, then you’d stand a much greater chance of killing the tumour before you kill the patient!
  
  Hopes that helps?

Question: what do you mean by "targeted drug delivery system"