 Upon arrival on the morning of the study visit, the nursing staff will ask the study subject to provide verbal confirmation that they took the KI pill and will document and record on the study flow sheet the approximate time that the subject took the tablet. If the pill was not taken within the allowed time range of 6:00 AM to 10:00 AM, the subject will not be able to participate in the study visit. A research team member will obtain informed consent from the participant and a copy of the consent will be given to the subject. The nursing staff will measure and record the subjects height, weight, blood pressure, temperature, pulse rate, respiration rate; confirm that the subject has not experienced any changes in physicalpsychological health since the screening; and collect a baseline urine sample. As outlined above, if three weeks or more has elapsed since the health screening, women of childbearing age will be administered a urine pregnancy test, prior to the insertion of the IV lines, using an aliquot of the baseline urine sample. The test kits used will be purchased from a local pharmacy by the site principal investigator or her delegate and provided to the CTRC staff. Nursing will interpret the results of the test and the principal investigator will verify a negative result prior to initiation of the GFR measurement. If the test yields a positive result, the study visit will be immediately terminated. 