Excretion of amines and their metabolites by two patients in hepatic coma treated with L‐dopa

Two patients in hepatic coma were treated with L ‐dopa. The first patient showed clear clinical improvement, but the second patient did not. Analyses of urinary metabolites indicated that L ‐dopa was not absorbed by the second patient. There was evidence that L ‐dopa had the following beneficial effects in the first patient: (1) increased production of urine, which could have been accompanied by increased excretion of toxins; (2) displacement of tyramine from transmitter sites (because increased excretion of p‐hydroxyphenylacetic acid, a major metabolite of tyramine, occurred during L ‐dopa treatment in patient 1); (3) replenishment of dopamine, and to a much lesser extent, norepinephrine, at central or peripheral neuroeffector junctions; and (4) scavenging of methyl groups by L ‐dopa, because ratio of methylated amines to catecholamines was higher than normal in both comatose patients before L ‐dopa treatment, and this ratio decreased during L ‐dopa treatment in patient 1. Clinical Pharmacology and Therapeutics (1983) 34 , 390–398; doi: 10.1038/clpt.1983.185