When I have done the PC I used a tincture that contained the same ingredients as Clarkia, I didn't see any criters but they say the majority of parasites are microsopic.
Many folks round here like both the Humaworm stuff of MHs Old Amish dewormer. The Humaworm stuff is fairly inexpensise and looks like it's easy to use in pill form and thats what I'm leaning towards for my next PC.