Why is levamisole used to cut cocaine?

It has the same genetics make up. So many of them are so close you would have to be a chemist to know the differences . So who has that kinda of time when at a drug deal . I really believe the C.I.A is putting it in to track users ?? who goes to the Doctor and says I feel like i got the flue and by the way I been doing a lot of Coke ?? So the doc treat you for the flue no help .. Be honest with the doc it privileged INFO under the H.I.P.A law ? so want to live tell doc all if not your on your own !