THE ANTISEROTONIN AGENT PIZOTIFEN DOES NOT INCREASE ENDURANCE PERFORMANCE IN HUMANS

This study investigated the effect of the serotonin receptor antagonis t pizotifen on endurance performance during treadmill exercise in huma ns. Eight healthy men exercised to exhaustion on a treadmill at an int ensity corresponding to 70% of their maximal oxygen uptake (VO2max). P izotifen was administered orally in a 1-mg dose 5 h before the start o f exercise. The study was double blind, using a randomized, placebo-co ntrolled crossover design. Oxygen uptake, heart rate, and ratings of p erceived exertion were measured and blood samples taken for determinat ion of concentrations of lactate, glucose, amino acids, ammonia, and h aematocrit. Measurements were made at intervals of 30 min during the r un and at exhaustion. There was no significant difference between the placebo and the pizotifen trials for any of the variables except for t he plasma free-tryptophane: branched chain amino acid ratio which was somewhat lower after pizotifen at postexercise. Pizotifen did not incr ease exercise time to exhaustion, which was even shorter after pizotif en than after placebo in seven out of the eight subjects; the differen ce between pizotifen and placebo did not reach the level of statistica l significance [109.4 (SD 6.7) min after pizotifen versus 119.8 (SD 12 .5) min after placebo]. The results do not support the hypothesis that there is a central component to fatigue which is mediated by the sero toninergic neurones.