Comparison of bromosulphthalein and indocyanine green clearance in sheep

The kinetics of indocyanine green removal from the blood after a single intravenous injection were measured in sheep and compared with those of a single dose of bromosulphthalein given to the same animals 48 hours later. A single dose of 1.5 mg kg-1 of indocyanine green (ICG) was cleared in a double exponential manner. The hepatic uptake of ICG was not significantly different from that of bromosulphthalein (BSP) but its rate of excretion in bile was significantly lower (P < 0.05) and its rate of plasma reflux significantly higher (P < 0.05). The plasma distribution volumes of the two compounds were similar but the mean (SD) plasma clearance of ICG (435 [228.6] ml min-1) was significantly lower than that of BSP (626 [291.9] ml min-1) (P < 0.05). The retention of ICG 30 minutes after the injection was significantly higher than that of BSP (P < 0.01).