The present invention discloses the use of L-Histidine to reduce Gadolinium accumulation into target organs, preventing its toxic effects, after administration of gadolinium based contrast agents. The invention thus, also disclose the use of L-Histidine to prevent the NSF syndrome in patients with renal functionality impairment. A kit of part is also disclosed by the use of which toxicity associated to free Gd3+, deriving from GDBCA, is prevented by oral administration of L-histidine before administration of the contrast agent. A method for the prevention of toxic metal accumulation which consists in the administration, preferably by the oral route, of L-Histidine is also disclosed. L-Histidine is preferably administered as a single oral dose comprised from 0.2-20 g.