Human performance after a barbiturate (heptabarbitone).

1 The residual effects of heptabarbitone given overnight were studied by an adaptive tracking technique. Decrements in performance were observed at the 10 h interval after 200 mg, at the 10 h and 13 h intervals after 300 mg and at the 10 h, 13 h, 16 h and 19 h intervals after 400 mg of the drug. Decrements in performance at each interval and the persistence of the effects were dose related. 2 Subjective assessments of performance correlated with measured performance, but the subjects, as a group, over-estimated their performance after placebo and heptabarbitone. With heptabarbitone (400 mg) highly significant decrements in performance persisted to the 19 h interval after ingestion, but subjective assessments of performance to the 19 h interval did not differ significantly from subjective assessments of control activity of the day before. 3 Individual blood concentrations of heptabarbitone did not give a significant correlation with individual performance decrements, though the blood concentrations and performance decrements at each dose were related.