Influence of premedication with diazepam or morphine on the induction dose of eltanolone

This study examined the influence of premedication with morphine or diazepam on the dose of eltanolone, a steroidal intravenous anaesthetic agent, required to induce anaesthesia.

Two hundred and sixteen patients, aged 18 to 65 years, were randomly assigned to receive premedication with diazepam 10 mg orally, morphine 10 mg intramuscularly, or placebo. The double-dummy technique was used to maintain blinding. Eltanolone 0.16-0.75 mg x kg(-1) was given intravenously over 20 s. At the commencement of injection patients were instructed to begin counting; if the patient ceased counting within 120 s and failed to respond to commands to continue, anaesthesia was considered to have been induced. The dose required to anaesthetise 50% of patients (ED50) was determined by logistic regression.

The ED50 (95% confidence interval) of eltanolone in patients who received placebo premedication was 0.31 (0.27-0.34) mg x kg(-1). It was reduced slightly and nonsignificantly by premedication with diazepam, to 0.27 (0.24-0.30) mg x kg(-1), or morphine, to 0.26 (0.23-0.29) mg x kg(-1). Involuntary movement occurred in 65% of placebo premedicated patients. Its incidence was not significantly reduced by diazepam (57%), but was significantly (P<0.001) reduced by morphine (37%). Morphine premedication was, however, associated with a significant (P<0.01) increase in the incidence of apnoea (21%) compared to placebo premedicated patients (4%).

Premedication with diazepam or morphine had little influence on the dose of eltanolone required to induce anaesthesia.