Metal complexes of bis-indole compounds and aqueous pharmaceutical compositions containing them

According to the invention there is provided complexes formed between a bis-indole compound and a bi- or multivalent metal ion, as well as a process for the preparation of a pharmaceutically acceptable metal complex of a bis-indole compound and, optionally, aqueous pharmaceutical compositions containing said metal complexes which are of substantially increased stability, in which process a solution of a bis-indole compound or a pharmaceutically acceptable salt thereof in an aqueous medium is reacted with a non-toxic water soluble salt of a bi- or multivalent metal capable of complexation, at a pH of 3.0 to 6.0, optionally in the presence of or followed by the addition of a conventional pharmaceutical carrier and/or further additive, or, if desired, the obtained complex is isolated. Specifically, the complexes of vinblastine and vincristine with Zn(II), Ca(II) or Mg(II) are disclosed.