Thiopentone and methohexitone enantiomers do not act stereoselectively on the oxidative response in human neutrophils in vitro.

To elucidate potential stereoselective effects of single barbiturate isomers, we compared the inhibitory potency of single thiopentone enantiomers, two isomer-enriched mixtures of methohexitone and racemic mixtures of both barbiturates on the fMLP-induced neutrophil oxidative response. A suppression of the response to 50% compared to control required a 100-fold therapeutic concentration of methohexitone, while therapeutic concentrations of the thiopentone racemate led to a significant inhibition (relative fluorescence of neutrophils 0.46 +/- 0.03 compared to fMLP controls). The racemate of thiopentone produced significantly greater inhibition than the single enantiomers. Stereoselectivity in favor of one isomer could not be shown for both barbiturates. The greater inhibition by the thiopentone racemate might suggest two separate binding sites for the enantiomers which are positively coupled.