Post-hypoxic intention myoclonus treated with 5-hydroxytryptophan and an extracerebral decarboxylase inhibitor

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Abstract
Post‐hypoxic intention myoclonus successfully treated by long‐term administration of the combination of 5‐hydroxytryptophan and carbidopa is described. Persistent euphoria and diarrhoea were essential side effects. Methysergide (12 mg/day) blocked the therapeutic effect, indicating a specific serotoninergic function of precursor loading with 5‐hydroxytryptophan. Tryptophan (8 g/day) had no effect on the myoclonus suggesting a reduced tryptophan hydroxylase activity. Plasma concentrations of 5‐hydroxytryptophan in the range of 10–30 micromoles per liter were obtained during maintenance therapy with 900 mg 5‐hydroxytryptophan per day in combination with 150 mg carbidopa per day.