Toxicological assessment of gadolinium release from contrast media.

In vivo gadolinium release was evaluated for MultiHance, Omniscan and Gadovist estimating gadolinium content in liver, kidneys, spleen, femur and brain after single or repeated intravenous administrations to rats at 1 mmol/kg. Gadolinium acetate (GdAc) at a daily dose of 0.03 mmol/kg and physiological saline were used as positive and negative controls, respectively. No changes in blood chemistry, haematology nor histopathology were seen with any of the tested contrast media, whereas an increase in white blood cell count and in serum cholesterol were found after GdAc at 0.18 mmol/kg cumulative dose. Analogously, gadolinium content in target organs (as % of injected dose) after any of contrast media was 100-200 times lower than after GdAc, either after single or repeated administrations. Under these experimental conditions, the rank of residual gadolinium found in these organs was GdAcOmniscan >Gadovist >MultiHance. Depopulation of lymphocytes in periarteriolar lymphatic sheaths (PALS) areas of the spleen was noted in rats treated with a single dose of GdAc sacrificed 24h post-dosing, but not in repeated dose rats sacrificed 48 h after last dosing. It was, therefore, concluded that this was a transient phenomenon and that PALS are rapidly repopulated with lymphocytes. With all contrast media, gadolinium content after a 2-day washout following a 3-week repeated administration period was lower than the amount found 24h after a single administration. Accordingly, the observed gadolinium content in organs should actually be in a complexed form (possibly the injected complex) which is subjected to elimination.