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Manganese is a hard but brittle grayish-white metallic element (symbol Mn; atomic no. 25) that occurs in nature chiefly in the form of its oxides, but is also found as a sulfide (for example in alabandite), carbonate (ankerite, dialogite, and rhodochrosite), niobate and tantalate (columbite), silicate (piedmontite, rhodonite, spessartite, and tephroite), arsenate (synadelphite), and tungstate (wolframite).
The inorganic manganese salt potassium permanganate is used as a local anti-infective, an astringent, and a powerful deodorant and cleanser.
Manganese is often present in mineral supplements, in hemopoietic formulations, and in some solutions for par-enteral nutrition. Trace elements are required in patients receiving long-term parenteral nutrition [ ], and the use of manganese has been reviewed [ ].
Mangafodipir trisodium (Mn DPDP; Teslascan, Nycomed, Oslo) is a chelate complex containing manganese (II) ion bound to fodipir, used as a hepatobiliary contrast agent [ ]. After injection, mangafodipir trisodium undergoes net transmetalation with endogenous zinc (II) ion and removal of the two phosphate groups to give two metabolites, manganese dipyridoxal ethyldiamine diacetate and zinc dipyridoxal ethylenediamine diacetate. The transmetalation with zinc is associated with a transient reduction in serum zinc concentrations, which normalize within about 24 hours after injection. About 14–20% of the manganese is excreted in the urine and 52–61% is excreted in the feces over 4 days. About 92% of fodipir is eliminated within 24 hours. Mangafodipir trisodium is mainly indicated to enhance the MRI T1-weighted images that are used in the detection, localization, and characterization of hepatic lesions. Normal liver parenchyma takes up the manganese and becomes bright, resulting in clear demarcation of abnormal parenchymal lesions.
LumenHance (Bracco Diagnostics Inc, Princeton, NJ) is a gastrointestinal MRI contrast agent based on manganese chloride.
Finally, as with other metallic elements, non-medical exposure to manganese can occur, particularly in occupational settings, and can cause neurotoxicity [ ].
The toxic effects of manganese in dogs [ ] and humans [ ] tend to involve the heart, liver, and nervous system, but some endocrine effects can occur. The general toxicity of manganese [ ] and its neurotoxicity [ ] have been reviewed.
Two cases of manganese intoxication during intermittent parenteral nutrition have been reported [ ]. In one case, manganese had been given once or twice a week for 4 years and in the other case twice a month for 5 years. Both patients had mild headache and dizziness. One had mild hepatic dysfunction. After withdrawal of manganese the symptoms all disappeared. Patients should be carefully monitored when receiving long-term parenteral nutrition including manganese, even when the manganese dose is small and administration infrequent.
In a phase III study 546 patients with suspected or known focal liver lesions received intravenous mangafodipir trisodium 5 μmol/kg before MRI examination [ ]. There were 195 adverse effects in 123 (23%) patients; only 72 were considered to be related to the contrast medium. Most common were nausea (7%), headache (4%), vomiting and abdominal pain (2% each), chest pain and palpitation (1% each), and hypertension, flushing, vasodilatation, and hypotension (under 1% each). Injection-associated reactions included heat (49%) and flushing (39%). Most of the adverse events (65%) were moderate and 7% were severe. Changes in laboratory values (full blood count, electrolytes, serum creatinine, and liver function tests) and vital signs (pulse, blood pressure) were generally transient, not clinically significant, and did not require treatment. The authors concluded that exposure to mangafodipir trisodium is not associated with short-term risks.
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