Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

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Burm, A.G. et al.

Pharmacokinetics of the enantiomers of mepivacaine after intravenous administration of the racemate in volunteers.

The pharmacokinetics of R(-)-mepivacaine and S(+)-mepivacaine were investigated in 10 healthy volunteers. The volunteers received racemic mepivacaine, hydrochloride (dose 60 mg) via a 10-min intravenous infusion. Blood samples were collected at gradually increasing intervals until 8 h after the start of the infusion. Plasma concentrations of the enantiomers were determined with a stereoselective high-performance liquid chromatographic (HPLC) method. Unbound fractions of the enantiomers were determined using equilibrium dialysis. The unbound fraction of R(-)-mepivacaine (mean +/- SD: 35.6% +/- 4.5%) was larger (P < 0.0001) than that of S(+)-mepivacaine (25.1% +/- 4.6%). The total plasma clearance and steady-state volume of distribution of R(-)-mepivacaine, based on total plasma concentrations (total plasma clearance [CL] = 0.79 +/- 0.12 L/min; volume of distribution at steady state [VSS] = 103 +/- 14 L) as well as on unbound plasma concentrations (plasma clearance of unbound drug [CLu] = 2.24 +/- 0.30 L/min; volume of distribution of unbound drug at steady state [Vuss] = 290 +/- 32 L), were larger (P < 0.0001) than those of S(+)-mepivacaine (CL = 0.35 +/- 0.06 L/min; Vss = 57 +/- 7 L; CLu = 1.43 +/- 0.24 L/ min; Vuss = 232 +/- 30 L). The terminal half-life (t1/2,Z) and mean residence time (MRT) of R(-)-mepivacaine (t1/2,Z = 113 +/- 17 min; MRT = 131 +/- 15 min) were shorter than those of S(+)-mepivacaine (t1/2,Z = 123 +/- 20 min, P < 0.02; MRT = 165 +/- 24 min, P < 0.0001). This study demonstrated a marked difference in the pharmacokinetics of the enantiomers of mepivacaine. The stereoselectivity can be partially explained by a difference in the plasma protein binding of the enantiomers.[1]

References

Pharmacokinetics of the enantiomers of mepivacaine after intravenous administration of the racemate in volunteers. Burm, A.G., Cohen, I.M., van Kleef, J.W., Vletter, A.A., Olieman, W., Groen, K. Anesth. Analg. (1997) [Pubmed]

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