Can long term MiraLax (polyethylene glycol) become toxic due to buildup in the body?? Neurological/cardiovascular effects?? I have Gilbert's disease..

No. miralax (polyethylene glycol) stays in the Gastrointestinal tract and doesnt get absorbed into the body, so their should be no neurologic affects. Even if you have Gilbert's disease, which affects the liver, the miralax (polyethylene glycol) doesnt go to the liver at all. It just draws water into the intestinal tract.