Rapid simultaneous determination of eperisone, tolperisone, and tizanidine in human serum by using a MonoSpin® C18 extraction column and liquid chromatography/tandem mass spectrometry.

A method was developed for rapid toxicological analysis of eperisone, tolperisone, and tizanidine in human serum using a MonoSpin® C18 extraction column and LC/MS/MS. The method was validated for LOD, linearity, precision, and extraction recovery. This method was rapid with an LOD of 0.5 ng/mL, linearity range 1-500.0 ng/mL (r2 = 0.999), and RSD value below 14.6%. Extraction recovery from the sample was greater than 98.6, 98.8, and 88.5% for eperisone, tolperisone, and tizanidine, respectively. Results showed that combination of the MonoSpin C18 extraction column and LC/MS/MS is a simple and rapid method for the analysis of these three analytes, and a method is described for simultaneous quantitative determination of the analytes in human serum by LC/MSIMS. This method was used to determine the serum levels of eperisone in a patient with eperisone poisoning, and could be successfully applied for screening analyses in clinical cases other than poisoning.

Enantioselective separation and simultaneous determination of tolperisone and eperisone in rat plasma by LC-MS/MS.

Tolperisone and eperisone used as muscle relaxants possess one chiral center each and exist as two optical isomers for each drug. Therefore, enantioselective assays to measure each enantiomer in biological matrices are of great importance. In the present study a simple and complete reverse-phase liquid chromatography tandem mass spectrometric method for separation and enantioselective determination of tolperisone and eperisone in rat plasma was developed. The analytes were extracted from rat plasma by a simple protein precipitation method with acetonitrile as the extraction solvent. The enantioselective separation of analytes was achieved on a Cellulose Tris (4-chloro-3-methylphenylcarbamate) chiral column with a mobile phase of acetonitrile: 10 mM ammonium acetate in an isocratic mode of elution and mass spectrometric detection. The calibration curve for each enantiomer was found to be linear over 0.2 to 20 ng/mL for each enantiomer. The proposed method exhibited good intra- and interday precision (% CV) ranged between 0.95-6.05% and 1.11-8.21%, respectively. The intra- and interday accuracy for the proposed assay method ranged between 94.0-100.5% and 92.7-102.1%, respectively. The proposed method was validated as per regulatory guidelines.

Determination of tolperisone in human plasma by liquid chromatography/tandem mass spectrometry for clinical application.

We have developed and validated a simple, rapid, and sensitive liquid chromatography analytical method employing tandem mass spectrometry (LC-MS/MS) for the determination of tolperisone, a centrally acting muscle relaxant, in human plasma. After liquid-liquid extraction with methyl t-butyl ether, chromatographic separation of tolperisone was performed using a reversed-phase Luna C(18) column (2.0mm×50mm, 5µm particles) with a mobile phase of 10mM ammonium formate buffer (pH 3.5) - methanol (12:88, v/v) and quantified by tandem mass detection in ESI positive ion mode. The flow rate of the mobile phase was 250µL/min and the retention times of tolperisone and the internal standard (IS, dibucaine) were both 0.6min. The calibration curves were linear over a range of 0.5-300ng/mL (r>0.999). The lower limit of quantification, using 200µL human plasma, was 0.5ng/mL. The mean accuracy and precision for intra- and inter-day validation of tolperisone were within acceptable limits. The LC-MS/MS method reported here showed improved sensitivity for quantification of tolperisone in human plasma compared with previously described analytical methods. Lastly, the validated method was successfully applied to a pharmacokinetic study in humans.

Considerable interindividual variation in the pharmacokinetics of tolperisone HCl.

OBJECTIVE: The aim of this study was to determine the pharmacokinetic profiles of oral tolperisone hydrochloride in healthy volunteers. METHODS: After the oral administration of tolperisone hydrochloride, the plasma concentrations of tolperisone were measured in 15 healthy male Korean volunteers. The tolperisone concentration was determined using high-performance liquid chromatography with a C18 reverse-phase column. RESULTS: Very large interindividual differences in the AUC and Cmax were detected after oral tolperisone HCl. The AUC0-infinity, varied from 125.9-1,241.3 ng/ml x h, and the Cmax varied from 64.2 and 784.9 ng/ml. The tmax of tolperisone was 0.90 +/- 0.31 h and the mean half-life was 1.00 +/- 0.28 h. CONCLUSION: These results suggest that the pharmacological effect of oral tolperisone HCl varies between individuals, and the oral tolperisone HCl dose might need to be individualized.

HPLC determination of tolperisone in human plasma.

A simple high performance liquid chromatographic (HPLC) method was developed for the determination of tolperisone in human plasma. Tolperisone and internal standard (chlorphenesin) were isolated from 1 mL of plasma using 8 mL of dichlormethane. The organic phase was collected and evaporated under nitrogen gas. The residue was then reconstituted with 300 mL aliquot of mobile phase and a 100 mL aliquot was injected onto the C18 reverse-phased column. The mobile phase, 45% methanol containing 1% glacial acetic acid and 0.05% 1-hexanesulfonic acid was run at a flow rate of 1 mL/min. The column effluent was monitored using UV detector at 260 nm. The retention times for tolperisone and the internal standard were approximately 7.1 and 8.4 min, respectively. The standard curve was linear with minimal intra-day and inter-day variability. The quantification limit of tolperisone in human plasma was 10 ng/ mL. The proposed method has been applied to the determination of pharmacokinetic profile of tolperisone in Koreans. The Tmax of tolperisone in Koreans (0.94 +/- 0.42 h) was not significantly differ from that reported in Europeans (0.5-1 h), but the mean half-life in Koreans (1.14 +/- 0.27 h) was shorter than that in Europeans (2.56 +/- 0.2 h). The proposed HPLC method is simple, accurate, reproducible and suitable for pharmacokinetic study of tolperisone.

[Two complex suicidal poisonings with drugs and their medicolegal aspects]. / Dwa kompleksowe samobójcze zatrucia lekami w aspekcie orzecznictwa sadowo-lekarskiego.

The main subject of the study was a toxicological investigation of biological specimens coming from two cases of intoxication with mixture of drugs. Two young people decided to commit suicide by the use of mixture of drugs mainly analgesic in approximately equal doses. For one person the dose of drugs administered turned out to be fatal while second person survived with the symptoms of acute intoxication. The analysis carried out with the use of liquid chromatographic method with mass detection (HPLC/MS) confirmed the presence of mixture of drugs in blood of living person and in postmortem specimens of the victim in significant concentrations. The toxicological findings have delivered information for discussion in medico-legal and ethical aspects.

Long-lasting muscle relaxant activity of eperisone hydrochloride after percutaneous administration in rats.

Potency and duration of muscle relaxant activity of eperisone hydrochloride were examined after percutaneous administration in the intercollicular decerebrated rat rigidity model and compared to those of eperisone after intravenous injection. A continuous movement was loaded on the hindlimb of the rat model to maintain stable rigidity. The tonus of the hindlimb was recorded by EMG from the triceps surae and was quantified by using the public domain NIH Image program. Eperisone ointment administered percutaneously showed significant muscle relaxant activity at 8.4 cm2 (4.2 mg of eperisone)/rat. The effect was dose-dependent and lasted over 60 min. Intravenously injected eperisone showed significant activity at 1.25 mg/kg, but the decrease of tone was lost within 30 min after injection. Plasma eperisone levels were monitored in the same model, and they were well correlated to the dosage. These results suggest that percutaneously administered eperisone is absorbed efficiently and shows potent and long-lasting muscle relaxant activity.

Determination of tolperisone enantiomers in plasma and their disposition in rats.

A stereoselective assay for the determination of tolperisone enantiomers in plasma by high performance liquid chromatography was developed. Calibration curves obtained for the enantiomers were linear over plasma concentrations of 0.1-3.0 micrograms/ml with a detection limit of 20 ng/ml. Following intravenous bolus administration of 10 mg/kg of racemic tolperisone to rats, stereoselective disposition of tolperisone enantiomers was observed, and plasma concentrations were significantly higher for l-tolperisone than for d-tolperisone at 5, 15 and 30 min after administration. When either enantiomer was administered alone to rats, both enantiomers were found in plasma, indicating that a mutual chiral inversion occurs in the body.