Technetium-99m (99mTc) mercaptoacetyltriglycine: update on the new 99mTc renal tubular function agent

Semin Nucl Med. 1992 Apr;22(2):61-73. doi: 10.1016/s0001-2998(05)80082-0.


Technetium-99m (99mTc) mercaptoacetyltriglycine (MAG3) is a new renal radiopharmaceutical that was recently introduced as a 99mTc-labeled replacement for iodine-131 (131I) o-iodohippurate (OIH). Since its introduction, a wide variety of in vitro and in vivo studies have been performed to characterize the high-performance liquid chromatography (HPLC)-purified complex and kit formulations. [99mTc]MAG3 has a slower plasma clearance, a higher plasma protein binding, less red blood cell (RBC) penetration, a lower extraction ratio, and a smaller volume of distribution than OIH. Because of the slower plasma clearance, [99mTc] MAG3 cannot be used as a direct measurement of effective renal plasma flow. Simplified methods have been developed to calculate [99mTc]MAG3 clearances, as well as regression equations to convert these clearances to an equivalent OIH value. The image quality of [99mTc]MAG3 is superior to [131I]OIH; the renogram curves and the fraction of the dose of the two agents that appears in the urine are almost identical, even though the plasma clearance of [99mTc]MAG3 is only 50% to 65% that of OIH. [99mTc]MAG3 compares favorably with OIH in patients with a wide range of clinical problems. The radiation dose to a patient with normal renal function using standard imaging doses is higher for [99mTc]MAG3 than for [131I]OIH, but in patients with impaired renal function, the radiation dose from [131I]OIH is much higher than [99mTc]MAG3. [99mTc]MAG3 also provides superior image quality compared with [99mTc]diethylenetriaminepentaacetic acid (DTPA) in patients with impaired renal function, but it is important to note that [99mTc]MAG3 cannot be used to measure the glomerular filtration rate (GFR). [99mTc]MAG3 is the most promising 99mTc tubular function agent to date, and it has replaced OIH and [99mTc]DPTA in a number of institutions. However, there are physiologic differences between these three agents and, therefore, they should not be expected to behave identically in all clinical conditions.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Humans
  • Hypertension, Renovascular / diagnostic imaging*
  • Oligopeptides* / chemical synthesis
  • Oligopeptides* / pharmacokinetics
  • Organotechnetium Compounds* / chemical synthesis
  • Organotechnetium Compounds* / pharmacokinetics
  • Radioisotope Renography / methods*
  • Reagent Kits, Diagnostic
  • Technetium Tc 99m Mertiatide


  • Oligopeptides
  • Organotechnetium Compounds
  • Reagent Kits, Diagnostic
  • Technetium Tc 99m Mertiatide