I have read a book on it, one in particular by Doc Sutter, Paradigm Shift in Health Care, he did a Liver Flush before a parasite cleanse and his symptoms worsened. He had no idea what was happening until he came across a book by Dr. Hulda Clark that stated not to do it without parasite cleanse first.
I have also come across people on these forums who did a Liver Flush before a parasite cleanse and it made them very sick. I'm not sure of details of why, I have just read you shouldn't.
There's an order to it
Colon Cleanse/Parasite cleanse (can be done together)
then a liver flush... I suggest his book, docsutter.com