Effect of the NSAID diclofenac on 99mTc-MAG3 and 99mTc-DTPA renography.

Renal function and disease are commonly evaluated by radionuclide studies. The choice of radiopharmaceutical agent for various studies is crucial for proper interpretation. (99m)Tc-mercaptoacetyltriglycine ((99m)Tc-MAG3) is excreted almost exclusively by the renal tubules, whereas (99m)Tc-diethylenetriamine pentaacetic acid ((99m)Tc-DTPA) is predominantly excreted by glomerular filtration. The present study compared the effect of the nonsteroidal antiinflammatory drug (NSAID) diclofenac, which is the most commonly used drug to relieve kidney pain, on the kinetic behavior of administered (99m)Tc-MAG3 and (99m)Tc-DTPA in experimental animals. Two groups of 12 New Zealand White rabbits ((99m)Tc-MAG3 and (99m)Tc-DTPA) were used for the renography. Each rabbit served as its own control. The animals were given 60 mL of saline intravenously 30 min before each renographic study. A baseline study (control) was done by injecting 48 MBq (1.3 mCi) of (99m)Tc-MAG3, and renography was performed. Two days later, a single intravenous dose of diclofenac (2 mg/kg) (treated animals) was given, and after 20 min, (99m)Tc-MAG3 renography was performed. This procedure was repeated for the (99m)Tc-DTPA group after administration of 96 MBq (2.6 mCi) of the tracer. Dynamic images (as 2-s frames for the first minute and 30-s frames for the next 30 min on a 64 × 64 matrix) were acquired using a γ-camera equipped with a low-energy high-resolution collimator interfaced with a computer. Regions of interest were drawn over the whole kidneys. Time-activity curves were generated from the region of interest. Time to peak activity (T(max)), time from peak to 50% activity (T(1/2)), and the uptake slope of each kidney were calculated from the renograms for control and treated rabbits. Administration of diclofenac shifted the experimental renogram curves to the right, compared with the control curves, indicating that there was a delayed renal uptake of the 2 tracers and clearance of the radioactivity. The calculated average values of T(max) for control and treated rabbits using (99m)Tc-MAG3 were 1.8 ± 0.5 and 6.35 ± 0.4 min, respectively, whereas those of (99m)Tc-DTPA were 3.4 ± 0.4 and 18.2 ± 2 min, respectively. The T1/2 for control and treated rabbits for (99m)Tc-MAG3 were 3.2 ± 0.07 and 6.6 ± 0.07 min, respectively, whereas those for (99m)Tc-DTPA were 10.1 ± 1 and 35 ± 4 min, respectively. The differences were statistically significant (P < 0.05). This study showed that diclofenac delayed both T(max) and T1/2. The NSAID-induced kinetic changes were considerably greater for (99m)Tc-DTPA than for (99m)Tc-MAG3. On the basis of these findings, it is suggested that (99m)Tc-MAG3 be used to perform renography for studies involving the use of NSAID administration to decrease any change that may occur due to the type of tracer and not to the condition of the kidney.