Complexation behaviour of azathioprine with metal ions

Abstract The behaviour of complex formation of azathioprine, an immunosuppressant drag, with various metal ions has been investigated by the potentiometric titration method. Azathioprine is found to form 2:1 complexes with Co(II), Cu(II) and Ni(II) in the order Cu(II) > Ni(II) > Co(II). No complex is formed with Ba(II), Ca(II), Fe(III), Mn(II) or Zn(II). The stability constants for the complexes were calculated. These differ from those of 6-mercaptopurine, of which azathioprine is a prodrug but shows an independent activity.