The blood pressure in a dialysis patient is related to salt and water retention. A person with kidney failure should get adequate dialysis (thrice a week), should have minimal salt & water retention and if the B.P. is still high then the drugs that your father is already on should be fine. The doses of these need to be titrated to achieve the target. The maximum doses of Enam could go up to 10 mg twice daily, Seloken to 100 mg twice a day, Prazopress XL to 10 mg twice daily. However these dosages should be titrated only in consultation with the nephrologist taking care of your father.