Similar motor block effects with different disposition kinetics between lidocaine and (±) articaine in patients undergoing axillary brachial plexus block during day case surgery.

Aim: The aim ofthis investigation was to compare the clinical effects and pharmacokinetics of lidocaine and articaine in two groups of 15 patients undergoing axillary brachial plexus anesthesia. Method: The study had a randomized design. Thirty patients were allocated to one of the two groups. Each patient received either lidocaine (600 mg = 2.561 mMol + 5 μg/ml adrenaline) or articaine (600 mg = 2.113 mMol + 5 μg/ml adrenaline), injected via the axilla of the brachial plexus over a period of 30 seconds. Onset of surgical analgesia was defined as the period from the end of the injection of the local anesthetic to the loss ofpinprick sensation in the distribution of all three nerves. Results: The mean onset time of sensory block of the median nerve of both lidocaine and articaine were approximately 10 min. Lidocaine is biexponentially eliminated with a t 1/2 α of 9.95 ±14.3 min and a t 1/2 β of 2.86 ± 1.55 h. Lidocaine is metabolized into MEGX (mono-ethyl-glycyl-xilidide) (t max 2.31 ± 0.84 h; C max 0.32 ± 0.13 mg/l; t 1/2 β 2.36±2.35 h). Lidocaine total body clearance was 67.9± 28.9 l/h. Articaine is rapidly and monoexponentially eliminated with a t 1/2 β of 0.95 ± 0.39 h. The total body clearance of articaine is higher than that of lidocaine, 1133 ± 582 l/h vs 67.9 ± 28.9 l/h, respectively (p < 0.0001). The volume of distribution (V d ), of articaine is a factor 16 higher times than that of lidocaine (p<0.0001). Conclusion: For the axillary administration, lidocaine and articaine show similar pharmacodynamics with a different pharmacokinetic behavior and can therefore be used to the clinical preference for this regional anesthetic technique.