Althesin interaction with human plasma steroid binding globulins

The binding affinities of two steroid anaesthetics, alphaxalone (Alfx) and alphadolone acetate (Alfd), for testosterone-oestradiol-binding globulin (TeBG) and corticosteroid-binding globulin (CBG) were measured in human serum. In 8 male patients, the effect of i.v. administration of Althesin (a mixture of Alfx and Alfd) on the transport of testosterone (T) and cortisol (F) was studied. Both Alfx and Alfd bind to TeBG and CBG with a relatively high affinity (10(6)M-1). A significant change in the percentage of unbound T was observed during Althesin infusion, with no change in total T concentration or in the TeBG binding parameters. The results suggest that by interaction with TeBG binding sites Alfx and/or Alfd displaced T bound to TeBG, and transiently increased the percentage of unbound T. A significant increase in the concentration of F was observed during althesin infusion, while the percentage of unbound F and the CBG binding parameters were unchanged. The dose of Alfx and Alfd used was not sufficient to alter the transport of F during brief althesin anaesthesia in men.