Why is the disk diffusion technique not a perfect indication of how the drug will perform in vivo?

Question

Why is the disk diffusion technique not a perfect indication of how the drug will perform in vivo? What other factors are considered before using the antimicrobial agent in vivo?

Answer 1

the drug may not be absorbed efficiently by the body as expected. another factor is that the drug is broken down and the actual metabollites are doing the job.