Manganese Based MR Contrast Agents: Formulation and Clinical Applications

This paper discusses the development and clinical applications of positive manganese based MR contrast agents, including both intravenous (i.v.) and oral formulations. The i.v. formulation is a manganese-dipyridoxyl diphos- phate chelate which is commercially available; whereas the oral formulation is a mixture of MnCl2, alanine and Vitamin D3, which is currently under clinical trials. The compositions, preclinical studies and pharmacokinetics of both form- ulations are discussed. The main reported clinical difference between the two formulations is that i.v. administration ex- poses all the organs, whereas oral ingestion exposes only the enterohepatic circulation. Manganese based MR contrast agents are particularly suitable for detection of focal liver lesions due to their uptake by the mitochondria rich hepatocytes, and biliary delineation due to their biliary excretion; it can provide useful information in diffuse liver lesions. Further, the i.v. formulation can be used for focal pancreatic lesions.