Majority of drugs and their metabolites are excreted through urine. Few drugs are excreted through feces and bile. In kidney failure patients, the kidney is unable to clear the metabolites of medicines and causes drug retention, which is dangerous, or it causes delay in the excretion of drug. All Antidiarrheal drugs are excreted through urine. That is why in renal impair patients, these drugs are given with precaution.
Do you have the doctor's approval to use an anti-diarrheal medication? If you have a renal issue I really don't think you should be using ANY medication without the doctor's approval.
Call or make an appointment and talk to your doctor ASAP, please.