Urinary monoamine metabolite excretion in disorders of movement. Effects of amantadine and levodopa.
We have studied the urinary excretion of 1,4-methylhistamine (1,4-MeHm), 5-hydroxyindole-3-acetic acid (5-HIAA) and homovanillic acid (HVA) in patients with Parkinson's disease, choreiform movements and essential tremor. The effect of amantadine on urinary excretion has been measured in each group of patients as well as the effect of levodopa in patients with Parkinson's disease. In patients with Parkinson's disease, excretion of 1,4-MeHm and HVA was significantly lower than in controls. Patients with choreiform movements had a reduced excretion of HVA but trends toward low levels of 1,4-MeHm and, in patients with Huntington's chorea, elevated excretion of 5-HIAA, were not significant. In patients with essential tremor, urinary excretion of the amine metabolities studied did nof differ significantly from controls. Administration of amantadine to patients with Parkinson's disease was not followed by increased excretion of monoamine metabolites except in those patients who were already receiving anticholinergic drugs. This increase is not significant and there was no effect in other groups of patients. These findings lend no support to the view that amantadine has a general amine-releasing action although there is limited evidence for such an effect in Parkinson's disease. In addition to the expected increase in HVA excretion, administration of levodopa to Parkinsonian patients was followed by significantly reduced excretion of 1,4-MeHm and 5-HIAA. However, if amantadine and levodopa were given together, excretion of 5-HIAA was still reduced, but that of 1,4-MeHm was normal. Levodopa may thus modify the turnover of histamine, which appears to be reduced in Parkinson's disease, and this effect may be modified by amantadine.