Comparison between in vivo and in vitro pharmacokinetics of succinylcholine in humans.
OBJECTIVE
To compare the in vivo and in vitro pharmacokinetics of succinylcholine (SCh) in humans.


METHODS
A bolus of SCh 1 mg.kg(-1) (n = 7) or 2 mg.kg(-1) (n = 11) was given to 18 patients anesthetized with thiopental. Arterial blood samples for determination of in vivo SCh concentrations were collected every 30 s for 5 min. Another 20-ml blood sample was obtained before induction of anesthesia for determination of in vitro SCh. Concentrations of SCh were measured by high-performance liquid chromatography. In vivo and in vitro concentrations of SCh vs time data were analyzed by the one-compartment model.


RESULTS
The respective in vivo and in vitro pharmacokinetic parameters (SCh 1 mg.kg(-1) vs SCh 2 mg.kg(-1)) were as follows: Plasma clearance was 4.17 +/- 2.37 and 1.85 +/- 0.28 l.min(-1), P < 0.05, vs 2.91 +/- 2.01 and 1.27 +/- 0.43 l.min(-1), P < 0.05. Elimination half-life was 25.4 +/- 10.6 and 47.4 +/- 5.4 s, P < 0.002 vs 26.3 +/- 10.0 and 75.2 +/- 21.8 s, P < 0.00005.


CONCLUSIONS
These results suggest that the rapid disappearance of SCh from the circulation is due to diffusion out of the blood vessels rather than to enzymatic hydrolysis.
Kato
M
M
Department of Anesthesiology, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan.
Shiratori
T
T
Yamamuro
M
M
Haga
S
S
Hoshi
K
K
Matsukawa
S
S
Jalal
I M
IM
Hashimoto
Y
Y