The question, what are the effects physically on drug caused by an improper sampling, may be answered as follows.

Generally, the drug consists of the actual medicine substance and the supporting material. These components are mixed together to get a homogeneous drug.

Improper sampling means, that you don´t know reliably the degree of mixture and, as a consequence, the spatial distribution of the medicine substance in the drug portions to be selled.

W.R. ■