Midazolam potentiates thiopental sodium anesthetic induction in patients.
OBJECTIVE
To test the hypothesis that midazolam potentiates thiopental sodium-induced unconsciousness.


METHODS
Randomized, double-blind study.


METHODS
A university medical center.


METHODS
Fifty nonpremedicated ASA physical status I and II adult patients scheduled for eye surgery.


METHODS
Intravenous (IV) injections of thiopental sodium in doses ranging from 1.0 mg/kg to 4 mg/kg with or without the addition of midazolam 0.02 mg/kg.


RESULTS
Inability to open eyes on command was used as an end point of anesthesia and the dose-response curves were determined using a probit procedure. A dose of 0.02 mg/kg, which constitutes less than one-tenth of the hypnotic ED50 value for midazolam, potentiated thiopental sodium anesthesia. The thiopental sodium ED50 value was decreased from 2.4 mg/kg to 1.6 mg/kg (p less than 0.001). Midazolam also reduced individual variability in the response to thiopental sodium. As a result, the thiopental sodium dose that reliably induced any nonpremedicated patient decreased from 6 mg/kg (ED99 of 5.57 mg/kg) to 2.5 mg/kg (ED99 of 2.37 mg/kg).


CONCLUSIONS
A subhypnotic dose of midazolam potentiates thiopental sodium-induced unconsciousness. This effect suggests the possibility that midazolam enhances barbiturate binding.
Kissin
I
I
Department of Anesthesiology, School of Medicine, University of Alabama, Birmingham 35294.
Vinik
H R
HR
Bradley
E L
EL
D000328:Adult; D000771:Anesthesia, Intravenous; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004357:Drug Synergism; D006801:Humans; D008874:Midazolam / Q000494:pharmacology*; D008875:Middle Aged; D013874:Thiopental / Q000494:pharmacology*
D013874:Thiopental; D008874:Midazolam