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6318900 
Journal Article 
[Complexation properties of the ligand EOB-DTPA and the kinetic stability of Gd(EOB-DTPA)] 
Burai, L; Brücher, E; Király, R; Solymosi, P; Víg, T 
2000 
0 
Acta Pharmaceutica Hungarica
ISSN: 0001-6659 
70 
3-6 
89-96 
Hungarian 
11379036 
Due to the presence of the ethoxy-benzyl group, the lipophilicity of the complex Gd(EOB-DTPA)2- is higher than that of Gd(DTPA)2- and thus Gd(EOB-DTPA)2- can be used as a liver specific contrast agent in Magnetic Resonance Imaging. The stability constants of the complexes of Fe2+, Fe3+, Zn2+ and Cu2+ formed with EOB-DTPA practically agree with those of the respective DTPA complexes. The complexes of EOB-DTPA formed with larger metal ions, like Ca2+, Ba2+, Gd3+ and other lanthanides, exhibit larger stability constants than the complexes of DTPA by 0.5-1 logK unit. The stability constants of the complexes Ln(EOB-DTPA)2- increase with increasing atomic number till the middle of the series. For the elements Tb to Ho the logKLnL values are approximately equal and a weak decrease can be observed for the heaviest elements, probably because of steric hindrance between the functional groups. The exchange reactions between the complex Gd(EOB-DTPA)2- and Y3+ ions occur predominantly through the formation and rate determining dissociation of the mono- and diprotonated complexes. The rate constants characterizing these reaction pathways are lower by a factor of three than the respective rate constants, known for the dissociation of Gd(DTPA)2-. On the basis of its higher kinetic stability, Gd(EOB-DTPA)2- can be used for in vivo investigations in medical diagnosis.