Influence of phenylethanolamine on octopamine plasma determination in hepatic encephalopathy

Octopamine and phenylethanolamine levels were measured by a radioenzymatic procedure in 30 cirrhotic patients with and without hepatic coma and in 15 normal controls. Octopamine data were obtained either by direct extraction with 40% isoamyl alcohol in toluene according to Molinoff et al. (Molinoff, P.B., Landsberg, L. and Axelrod, J. (1969) J. Pharm. Exp. Ther. 170, 253), or after pre-extraction of phenylethanolamine with 3% isoamyl alcohol in toluene. Phenylethanolamine was statistically correlated with the grade of hepatic encephalopathy. Octopamine levels also appeared to parallel the grade of coma, although the values obtained after pre-extraction were lower and less significant than those obtained with 40% isoamyl alcohol in toluene extraction. The higher values of directly extracted octopamine are due to contamination of other beta-hydroxylated phenylethylamines, among which is phenylethanolamine.