Missing effect of etomidate on testosterone secretion in man

Comparative effects of etomidate and its fluoro analogue, R 8110 on testicular, adrenal and ovarian steroid biosynthesis

The effects, of etomidate and of its fluoro analogue, R 8110, on adrenal, testicular and ovarian steroid biosynthesis were compared using cultures of guinea-pig adrenal, rat adrenal capsular, rat testicular and rat ovarian granulosa cells. At a concentration of 100 nM, etomidate inhibited the adrenal 11-hydroxylation of glucocorticoid and mineralocorticoid biosyntheses, producing a decrease in cortisol and corticosterone and an accumulation of 11-deoxycortisol and 11-deoxycorticosterone in guinea-pig adrenal and rat capsular adrenal cell suspensions, respectively. At higher concentrations (greater than 10(-6) M), etomidate also inhibited ovarian oestradiol production, testicular androgen formation and ovarian progesterone synthesis. The latter action suggests an effect on ovarian aromatase, on testicular 17 alpha/17,20-lyase activities and finally on cholesterol side-chain cleavage. The fluoro analogue of etomidate, R 8110, was ten times less potent as an inhibitor of 11-hydroxylation and affected progesterone formation only slightly in adrenal cell suspensions. Testosterone production was less affected by R 8110 than by etomidate. The increase of progestins suggests that the 17 alpha/17,20-lyase activities are the most sensitive testicular enzymatic reactions to R 8110. For inhibition of ovarian oestradiol production, R 8110 was twenty times more potent than etomidate.

Adrenocortical suppression and other endocrine effects of etomidate

(+/-) Etomidate is a short-acting general anaesthetic given by the intravenous route. It has strong adrenal suppression capability initially shown in the rat and then observed in man. At present, the drug seems the most effective adrenocortical inhibitor on a molar basis in vitro. 11 beta-hydroxylase is the most sensitive target enzyme; 16 alpha-, 17 alpha-hydroxylase and cholesterol side-chain cleavage are inhibited by higher concentrations. (+) Etomidate was more active than the (+/-) and far more than the (-) stereoisomer. Etomidate blood concentrations greatly exceed those needed to block adrenal steroidogenesis both when used inappropriately by infusion for long-term sedation (such previously unrecognized drug-induced adrenal suppression has often proved fatal in severely-injured patients) and also when given in very low doses as an induction anaesthetic. Reactive ACTH increase is currently observed. Etomidate, in vivo, does not appear to affect testicular steroidogenesis although it shares an imidazole moiety with fungicide phenylimidazoles endowed with such an action. However, testosterone production may be reduced by high concentrations in vitro. Other gonadal hormones seem unchanged. Both basal and stress-induced blood prolactin levels are lowered by etomidate in the rat but probably not in man arguably through interference at brain level where the GABA-benzodiazepine receptor complex could be directly involved. Hence, endocrine and neuroendocrine interferences are unique non-anaesthetic effects of etomidate.

Comparison of the effects of etomidate and its fluoro analogue, R 8110, on plasma cortisol, 11 beta-deoxycortisol, 17 alpha-hydroxyprogesterone and testosterone concentrations in dogs

R 8110, an imidazole derivative, was shown to be clinically superior to etomidate for induction and maintenance of anaesthesia in dogs. The present study compared the effects of intravenous (i.v.) R 8110, etomidate and Ringer solution on cortisol biosynthesis by the adrenal gland in seven male labradors. A tetracosactide challenge was carried out 30 min after the i.v. injection of 3 mg/kg of both drugs and after i.v. Ringer solution (1 ml/kg). Etomidate and R 8110 both suppressed the cortisol response to tetracosactide almost completely and increased the plasma 11 beta-deoxycortisol levels more than 20 fold. Maximal 11 beta-deoxycortisol values were reached 120 min after R 8110, and not less than 300 min after etomidate. Plasma 17 alpha-hydroxyprogesterone and testosterone concentrations did not differ between placebo and R 8110 treatment, but they decreased after etomidate. These results indicate that the effects of R 8110 on steroid biosynthesis in dogs are less pronounced than those of etomidate and are largely limited to a temporary inhibition of the 11 beta-hydroxylase in the adrenal gland.