Comparison of the disposition kinetics of lidocaine and (+/-)prilocaine in 20 patients undergoing intravenous regional anaesthesia during day case surgery.
OBJECTIVE
The aim of this investigation was to compare the pharmacokinetics of lidocaine and prilocaine in two groups of 10 patients undergoing intravenous regional anaesthesia.


METHODS
The study had a randomized design. The patients were allocated to one of the two groups of 10. Each group received either lidocaine (200 mg = 0.855 mM) or prilocaine (Citanest, 200 mg = 0.909 mM), injected intravenously over a period of 30 s. Onset of the surgical analgesia was defined as the period from the end of the injection of the local anaesthetic to the loss of pinprick sensation in the distribution of all three nerves.


RESULTS
The mean onset time of surgical analgesia of lidocaine was 11.2 +/- 5.1 min and that of prilocaine was 10.9 +/- 6.0 min. After releasing the tourniquet, lidocaine is bi-exponentially eliminated with a t1/2 alpha of 4.3 +/- 2.1 min and a t1/2 beta of 79.1 +/- 31.2 min. Total body clearance was 0.86 +/- 0.39 litres/min. Prilocaine is rapidly and bi-exponentially eliminated with a t1/2 alpha of 3.0 +/- 1.6 min and a t1/2 beta of 29.9 +/- 15.7 min. The total body clearance of prilocaine is higher than that of lidocaine, 4.15 +/- 1.31 vs. 0.86 +/- 0.39 litres/min, respectively (P = 0.0007). Both compounds show comparable volumes of distribution (Vd, Vss and V beta) and a comparable t1/2 alpha (4.3 +/- 2.1 vs. 3.0 +/- 1.6 min; P = 0.1780). The t1/2 beta for the two compounds were different (P = 0031); 79.1 +/- 31.2 min for lidocaine and 29.9 +/- 15.7 min for prilocaine. The mean residence time (MRT) of lidocaine (193 +/- 233 min) also differed significantly from that of prilocaine (33.4 +/- 19.9 min; P = 0.0022).


CONCLUSIONS
Lidocaine is preferred for relatively long procedures and prilocaine for short procedures.
Simon
M A
MA
Department of Anesthesiology, Medisch Spectrum Twente, Enschede, The Netherlands.
Vree
T B
TB
Gielen
M J
MJ
Booij
L H
LH
D000328:Adult; D000771:Anesthesia, Intravenous; D000779:Anesthetics, Local / Q000097:blood / Q000493:pharmacokinetics*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008012:Lidocaine / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D011318:Prilocaine / Q000097:blood / Q000493:pharmacokinetics*
D000779:Anesthetics, Local; D011318:Prilocaine; D008012:Lidocaine