Ten patients will be invited to participate in the trial. After obtaining informed consent, the ten patients will be randomly assigned to one month of treatment with oral n-acetylcysteine 500mg or placebo twice daily for thirty days in addition to their regular therapy. At enrolment the patients will be educated and counselled about the trial and the intervention medication. Patients will also have a blood test (serum creatinine) that will allow the calculation of their renal function by use of the Cockroft Gault equation. Blood samples will also be frozen and stored. Patients will also undergo an ultrasound test of the function of their arm blood vessels. Both the blood test and the ultrasound test will be repeated at the completion of the thirty day trial period. Again the blood test sample will be frozen and stored. Subjects will then cross over to the other treatment arm for a further one month period, with the same testing at the end.
