Further evidence for the interaction of the antimalarial drug amodiaquine with ferriprotoporphyrin IX.

Evidence for complex formation of the antimalarial drug amodiaquine (AD) with ferriprotoporphyrin IX (FP) in aqueous medium is presented, in addition to previous preliminary data. A mole ratio of one between the complex components is determined for the insoluble complex at pH 6.7-6.8. Mössbauer data obtained at pH 7-8 and at higher concentrations in the millimolar range confirm the interactions existing between the complex components. These data are considered to aid in removing previous objections to a mechanism of antimalarial action involving complexes of FP with AD and related drugs.