Yeah I am not sure if eating then taking will help. But it is worth the try.
I may not always say what everyone wants to hear but I try to always be honest. I know what it is like with a very sick cham and having to go through the medication process. I know it is hard to watch them suffer and not be able to do anything. Just remember by medicating you are doing something.
Just be sure you follow proper cleaning. My understanding of Giardia is that they can reinfect themselves if they lick or eat from a place where fecal has been. Because the parasite comes out in the fecal.
@JacksJill would know much better than I on this though.