L-Histidine: failure to affect the sleep-waking cycle in man.

L-Histidine was administered to three patients with intractable narcolepsy (20 g/day for 2 weeks), to 4 normal volunteers (32.4 g/day for 5 days), and to a patient with progressive systemic sclerosis (48.6 g/day for 16 days). No effect was observed on noctural EEG sleep patterns in any of the subjects or on the symptoms of the patients with narcolepsy. These results fail to support the hypothesis that histamine is a waking factor.