Rotary pursuit, a measure of human performance, and plasma concentrations of promethazine

Promethazine in doses of 50 mg has demonstrated detrimental effects upon the performance of visual tasks. The purpose of the study was to examine the relationship between the blood concentration levels of promethazine and two human performance tasks. Fifteen paid healthy male volunteers completed a randomized five-way crossover design which included a 25 mg and 50 mg dose of the innovator dosage form, a 50 mg dose of a generic dosage form, a 50 mg solution dosage form, and a placebo. Serial blood samples were obtained in addition to performance measures of rotary pursuit and a simple force choice reaction time. Analysis of the forced choice reaction depicted a mild relationship with the blood concentration levels of promethazine. However, the measures of rotary pursuit, a more sensitive determinant of human motor performance, proved to be more related to both the promethazine blood concentration and the inherent learning which was confounded in the experiment. The degree of impaired pursuit performance and reaction time differences could be defined in terms of a linear relationship to the promethazine concentration.