Comparison of sulfobromophthalein and indocyanine green clearances in the cat

Plasma disappearances of sulfobromophthalein (BSP) and indocyanine green (ICG) given in single-dose IV injections to cats were measured. The BSP was given at a dose of 5 mg/kg of body weight; ICG was given at a dose of 1.5 mg/kg of body weight. The half-life, disappearance rate (percent per minute) and clearance (ml/min/kg) were determined during the initial phase of plasma dye elimination. The half-life for BSP was 2.2 +/- 0.7 minutes, and for ICG, 3.8 +/- 0.9 minutes. The disappearance rate for BSP was 34.7 +/- 10.1, and for ICG, 19.2 +/- 4.5. The clearance for BSP was 26.3 +/- 23.1 and for ICG, 8.6 +/- 4.1. The 30-minute percentage retention for BSP was 0.6 +/- 0.8% and for ICG, 7.3 +/- 2.9%. In the cat, ICG was cleared from the plasma less rapidly than BSP. There were no significant differences between males and females for these values. For both BSP and ICG, a significantly shorter half-life, faster disappearance rate, and lower 30-minute percentage retention were observed in the cat, compared with values observed in the dog given similar dye dosages. Clearance curves for BSP and ICG in the cat were similar to those in the dog, indicating that the 2 species may have similar volumes of dye distribution and excretory mechanisms. The results of the present study indicate that the 30-minute plasma level following a 5 mg/kg dose of BSP in normal cats is often too low for measurement, whereas the 30-minute plasma concentration of ICG following a 1.5 mg/kg dose is adequate. For the 30-minute dye retention test in the cat, ICG may be a preferred diagnostic agent.