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ICG binds with serum protein (lipo-protein, albumin, etc.) and is taken selectively by the liver. It is not observed in entero-hepatic circulation and not excreted from the kidney, but is excreted from the liver into bile. So, it is suitable for liver function test by determinating the rate of retention of the dye in the blood, the rate of disappearance of the dye in plasma or by assessing hepatic blood flow.
ICG is rapidly bound to protein in blood and is optically stabilized. So, wave-length of its maximum absorption, which is 780nm in aqueous solution, changes to 805nm immediately. Since 805nm comprises isobestic point at which absorption curve of oxidized form of hemoglobin in the blood intersects that of reduced form of hemoglobin in the blood, absorption is scarcely affected by the fluctuations in oxygen saturation of the blood so long as it is determined by the wave-length, 805nm.
ICG neither deposits in the skin nor accumulates in the blood. About 97% of the amount is excreted within 20 minutes after intravenous injection.
In presence of hepatic disorders, ICG is excreted from the liver.
Toxicology: Toxicity: Acute toxicity: LD50 of ICG by intravenous injection is 64.3mg/kg in mice and 87.1 mg/kg in rats.
Fetal test: No teratogenecity was noted in animal experiments using mice and rats. Any passage through placental barrier can't be seen in the pregnant women.
