I'm no expert or doctor here ............. but I'm going to recommend not using that stuff.
Just a few years back, doctors were prescribing Visicol tablets. These tablets were a concentrated sodium phosphate, for cleansing the bowels in prep for a colonoscopy.
Several tablets were to be taken orally with a lot of water over a period of time.
There has been litigation from people using this, and I think the FDA pulled this from the shelves.
It's my understanding that some people suffered acute phosphate nephropathy (renal failure) ............ among other problems.
Although the problems are primarily created from oral dosage in strong concentration, there is also info out there about taking the Fleet 4oz. enema.
And you're taking 64 ounces of it rectally. That solution is going up pretty high and is covering a lot of surface area in your intestines.
I highly recommend you do some research before you go any further.
You can start here: