Evaluation of high-performance liquid chromatography and mass spectrometry method for pharmacokinetic study of local anesthetic ropivacaine in plasma

We studied the viability of high-performance liquid chromatography and mass spectrometry (LC/MS) as a selective and sensitive analytical method for measuring blood concentrations of the local anesthetic ropivacaine. Ropivacaine was effectively separated using a,I reverse-phase Column and monitored at 275 m/z ion. The LC/MS method allowed measurement of concentrations of ropivacaine of lower than 75 ng/mL. The standard Curve was linear and in the range of < 1.5 mu g/mL. Recovery of ropivacaine in plasma samples was over 90% after precipitation of plasma protein with trichloroacetic acid. The method was tested oil the pharmacokinetics of plasma ropivacaine after single intravenous or Subcutaneous administration in rabbits. The pharmacokinetic parameters showed a one-compartment model and a mean elimination half-life of 0.54 +/- 0.05 h and 2.83 +/- 0.51 h after administration at doses of 0.4 mg/kg, i.v. and 5 mg/kg, s.c., respectively. These values were in approximate agreement with previously obtained results in dogs. The results of the present Study demonstrated that the LC/MS method was highly selective and sensitive for the measurement of ropivacaine, Indicating that it offers a Useful tool for monitoring the therapeutic effects and determining the pharmacokinetic parameters of this drug In blood.