Measurement of glomerular filtration rate by fluorescent excitation of non-radioactive meglumine iothalamate.

The clearance of non-radioactive meglumine Iothalamate (Conray 60), assayed by fluorescent excitation analysis, has been shown to be a good indicator of the glomerular filtration rate (GFR). Investigations in rats by the constant infusion technique showed a good correlation with insulin clearance. In a group of ten children and one adult, we obtained excellent agreement between GFR determinations by clearance of Conray 60 and I-125 sodium Iothalamate, using the single injection technique, and taking samples from 10 min to 4 hr after injection. The decay curve was resolved into two exponential components. We have also shown that the 3 and 4 hr samples, fitted to a single exponential function, yield good agreement with GFR determinations using a double exponential model. The GFR determination method presented here is accurate, simple, cost effective, and involves no radiation exposure to the patient.