Abstract
BackgroundBecause etomidate induces prolonged adrenal suppression, even following a single bolus, its use as an infused anesthetic is limited. Our previous study indicated that a single administration of the novel etomidate analog methoxyethyletomidate hydrochloride (ET-26-HCl) shows little suppression of adrenocortical function. The aims of the present study were to (1) determine the minimum infusion rate of ET-26-HCl and compare it with those for etomidate and cyclopropyl-methoxycarbonylmetomidate (CPMM), a rapidly metabolized etomidate analog that is currently in clinical trials and (2) to evaluate adrenocortical function after a continuous infusion of ET-26-HCl as part of a broader study investigating whether this etomidate analog is suitable for long infusion in the maintenance of anesthesia.MethodThe up-and-down method was used to determine the minimum infusion rates for ET-26-HCl, etomidate and CPMM. Sprague-Dawley rats (n = 32) were then randomly divided into four groups: etomidate, ET-26-HCl, CPMM, and vehicle control. Rats in each group were infused for 60 min with one of the drugs at its predetermined minimum infusion rate. Blood samples were drawn initially and then every 30 min after drug infusion to determine the adrenocorticotropic hormone-stimulated concentration of serum corticosterone as a measure of adrenocortical function.ResultsThe minimum infusion rates for etomidate, ET-26-HCl and CPMM were 0.29, 0.62, and 0.95 mg/kg/min, respectively. Compared with controls, etomidate decreased serum corticosterone, as expected, whereas serum corticosterone concentrations following infusion with the etomidate analogs ET-26-HCl or CPMM were not significantly different from those in the control group.ConclusionThe corticosterone concentrations tended to be reduced for the first hour following ET-26-HCl infusion (as compared to vehicle infusion); however, this reduction did not reach statistical significance. Thus, further studies are warranted examining the practicability of using ET-26-HCl as an infused anesthetic.
Highlights
Etomidate, one of the most frequently used intravenous anesthetics, has many favorable properties, such as its ability to maintain hemodynamic stability and generate low incidences of respiratory depression and anaphylaxis
Serum corticosterone concentrations increased over time in all groups after drug infusion and adrenocorticotropic hormone (ACTH) stimulation
We evaluated the minimum infusion rate (MIR) of etomidate, ET-26-HCl, and CPMM by recording in anesthetized rats either a positive (+) or no (−) reaction to a painful stimulus, an up-and-down design method previously described (Li et al, 2012)
Summary
One of the most frequently used intravenous anesthetics, has many favorable properties, such as its ability to maintain hemodynamic stability and generate low incidences of respiratory depression and anaphylaxis. Our previous study indicated that a single administration of the novel etomidate analog methoxyethyletomidate hydrochloride (ET-26-HCl) shows little suppression of adrenocortical function. The aims of the present study were to (1) determine the minimum infusion rate of ET-26-HCl and compare it with those for etomidate and cyclopropyl-methoxycarbonylmetomidate (CPMM), a rapidly metabolized etomidate analog that is currently in clinical trials and (2) to evaluate adrenocortical function after a continuous infusion of ET-26-HCl as part of a broader study investigating whether this etomidate analog is suitable for long infusion in the maintenance of anesthesia. The up-and-down method was used to determine the minimum infusion rates for ET-26-HCl, etomidate and CPMM. Etomidate decreased serum corticosterone, as expected, whereas serum corticosterone concentrations following infusion with the etomidate analogs ET-26-HCl or CPMM were not significantly different from those in the control group. Further studies are warranted examining the practicability of using ET-26-HCl as an infused anesthetic
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