Ferrioxamine B derivatives as hepatobiliary contrast agents for magnetic resonance imaging

Succinyl (SDF), phenylsuccinyl (PSDF), glutaryl (GDF), and phenylglutaryl (PGDF) derivatives of desferrioxamine B (DF) have been synthesized. In rats given the 59Fe(III) chelates of each these ligands at tracer levels, 82-94% of the 59Fe was eliminated within 1-2 days. 59Fe given as DF, SDF, and GDF chelates was excreted primarily in the urine, while nearly 50% of that given as PSDF and PGDF was excreted in the feces. Correspondingly, Fe-DF, Fe-SDF, and Fe-GDF (0.2 mmol/kg) produced early, marked renal, but no gastrointestinal magnetic resonance imaging (MRI) enhancement. Fe-PSDF and Fe-PGDF (0.2 mmol/kg) produced marked and rapid MRI enhancement of the upper small intestine. In animals with cannulated bile ducts, 59Fe from 59Fe-PGDF (carrier added, 0.1 mmol/kg) appeared rapidly in the collected bile, but not in the intestinal contents, proving that the contrast agent reaches the bowel via the bile. These changes in the excretion and MRI enhancement patterns brought about by the presence of a phenyl substituent apparently were not related to changes in lipophilicity or protein binding.