Evaluation of Renal Drug Transport in Healthy Volunteers

The purpose of this study is to measure GFR (using iothalamate clearance) and renal tubular function (using PAH clearance) in healthy subjects. The protocol will be approved by the University of Maryland IRB and the General Clinical Research Center (GCRC) advisory committee (GAC). Following the informed consent process, each subject will be evaluated for past medical history, undergo a physical examination and routine laboratory tests (including urinary protein:creatinine ratio) conducted within 1 month prior to the study visit. Day 1: Vital signs (heart rate, blood pressure, respiratory rate) will be recorded hourly throughout each study visit. Subjects will have intravenous catheters inserted into forearm veins of each arm for blood collection and intravenous infusion iothalamate and PAH. From 30 minutes before marker administration until the end of each evaluation period, subjects will remain in a semireclined position except during urine collections. A constant-rate infusion will then be initiated at 1 mL/min for a total of 3 hours, with the concentration in the infusate determined based on the patient's estimated renal clearance and target plasma concentration of 10 mg/L and 15 mg/L for iothalamate, and PAH, respectively. Day 2: Washout Day 3: Subject will begin taking probenecid. Day 4 (Study visit #2): Subject will be admitted to the GCRC at 8AM. The final dose of probenecid will be administered. The renal function test will then be conducted as described for study visit #1 above. Day 11: Subject will be contacted for monitoring of adverse events according to GCRC procedures.