A TOXICOLOGIC RISK FOR USING MANGANESE COMPLEXES - A LITERATURE SURVEY OF EXISTING DATA THROUGH SEVERAL MEDICAL SPECIALTIES

This article summarizes data from the literature about biologic functi ons, toxicity, and biokinetics of manganese to help the reader assess the importance of complex stability of manganese-based contrast agents . Free manganese may present a greater risk than free gadolinium, espe cially because it has a physiologic role and can therefore trigger mul tiple functions, Of particular interest are the deleterious effects of manganese on the central nervous system (it can cross the intact bloo d-brain barrier) and on developing life (it penetrates the placental b arrier as well and is teratogenic), After intravenous contrast injecti on, normal (enteral) regulation mechanisms for manganese homeostasis a re bypassed, and there is a danger of individual overdosing, Excess ma nganese, for example in patients with chronic liver disease or with ch ronic parenteral nutrition, has already been detected by magnetic reso nance imaging in the basal ganglia and was found to coincide with neur ologic symptoms. Decomplexation with release of free manganese substan tially prolongs the elimination of the metal because manganese can be excreted only slowly via the biliary system, This may be of particular importance in patients with impaired hepatic function. Although minim al amounts of free manganese ions are not considered harmful to the hu man body, significant decomplexation of manganese complexes will requi re careful analysis of the diagnostic benefit versus the potential ris k posed by the free metal ions.