Determination of muscle relaxants pancuronium and vecuronium bromide by capillary electrophoresis with capacitively coupled contactless conductivity detection.

A novel capillary electrophoretic method for the separation of pancuronium (PM) and vecuronium (VM) ions utilizing capacitively coupled contactless conductivity detection was devised and validated. The separation was carried out in bare fused-silica capillaries (50 µm id, 75/45 cm) at 25°C. Optimal BGE was 50 mM borate buffer of pH 9.5 containing 12.5 mg/mL of (2-hydoxypropyl)-γ-CD. The samples were injected hydrodynamically at 1000 mbar for 3 s. Separation was performed at +30 kV. Under such conditions the PM and VM were base-line resolved and the separation took < 4 min. For quantification phenyltrimethylammonium iodide was used as internal standard. Calibration curves were linear for both pancuronium bromide (PMB) and vecuronium bromide (VMB) in the range 25-250 µg/mL with r> 0.9968. The limits of detection were 7 and 6 µg/mL for PMB and VMB, respectively. The accuracy tested by recovery experiment at three concentration levels of added PMB and VMB was satisfactory (95.7-102.7%, n =3, with RSD < 2.61%). The method was successfully applied to the assay of PMB and VMB in commercial injection solutions.

Pancuronium bromide (Pavulon) isolation and identification in aged autopsy tissues and fluids.

The isolation and detection of pancuronium bromide was developed for aged autopsy samples to identify and confirm this compound in questioned tissue samples. A novel protocol was optimized for the isolation of the target drug in highly decomposed tissues. Solid-phase extraction (SPE) cartridges containing styrene-divinylbenzene were investigated. This polymer retained quaternary drugs and facilitated sequential elution upon washing with commonly available solvents. The semi-purified SPE samples were prescreened by pyrolysis GC-MS. A candidate specimen was then confirmed by microbore high-performance liquid chromatography/electrospray-ionization/mass spectrometry (microHPLC-ESI-MS/MS) with a triple-quadrupole mass spectrometer. The developed procedures provided a qualitative or semiquantitative (at best) basis for the investigation of difficult cases involving overdoses of polar drugs.

Validation of a high-performance liquid chromatography method for the determination of pancuronium in Pavulon injections.

A new high-performance liquid chromatography (HPLC) method was developed for the quality control of pancuronium bromide and its degradation products. The HPLC method used a 5-microm Supelcogel ODP-50 (150x4 cm) column with acetonitrile-CH3OH-water-F3CCOOH (20.5:74.9:0.1, v/v) as the mobile phase (pH value 2.0 adjusted with trifluoroacetic acid) at a flow-rate 0.8 ml/min and UV detection at 210 nm. The Beer's law plots were found to be linear over the concentration range 0.4-1.2 mg/ml of pancuronium bromide and 0.04-0.08 mg/ml of desacetyl degradation products (R2=0.9995). The RSD of the peak areas was 1.09% and the recovery was 102.43%. The RSD value shows good precision, acceptable accuracy and reproducibility of the new method for the determination of pancuronium bromide in presence of its desacetyl degradation products. The method is rapid and sensitive enough to be used for Pavulon injection analysis.

Instability of pancuronium in postmortem blood and liver taken after a fatal intramuscular Pavulon injection.

The present study was designed to determine the stability of pancuronium in postmortem blood and liver during storage. Results were obtained using the method by Kerskes et al. [C.H.M. Kerskes, K.J. Lusthof, P.G.M. Zweipfenning, J.P. Franke, The detection and identification of quaternary nitrogen muscle relaxants in biological fluids and tissues by ion-trap LC-ESI-MS, J. Anal. Toxicol. 26 (2002) 29-34.], modified and validated in our laboratory. Target analytes were isolated after enzymatic hydrolysis followed by solid phase extraction (BondElut C18 column). Internal standardisation was carried out using laudanosine and the target ions were monitored by LC-ESI-MS (monitoring ions m/z 358 for IS and 286 for pancuronium). Materials were taken from a 46-year-old woman, who had been found dead. A syringe (2 ml) and an empty ampoule of Pavulon (4 mg/2 mL) were found in her hand. The residual volume of fluid in the syringe was 0.7 ml. An autopsy was performed six days after death. It revealed a needle mark on the left thigh. Postmortem materials (muscle from the injection site, blood and liver) and the syringe with fluid were stored for four months in a freezer at -20 degrees C. The initial pancuronium concentrations were 81 ng/mL in blood and 532 ng/g in liver. The analyte was stable when stored at -20 degrees C in blood even up to seven months. In liver samples its concentrations were variable. Pancuronium in blood stored at 20 degrees C underwent degradation very rapidly. After three months of storage these blood samples had concentrations not greater about 10% of the initial value. The degradation patterns of pancuronium depended on temperature and the biological matrix.

The detection and identification of quaternary nitrogen muscle relaxants in biological fluids and tissues by ion-trap LC-ESI-MS.

Quaternary nitrogen muscle relaxants pancuronium, rocuronium, vecuronium, gallamine, suxamethonium, mivacurium, and atracurium and its metabolites were extracted from whole blood and other biological fluids and tissues by using a solid-phase extraction procedure. The extracts were examined by using high-performance liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). The drugs were separated on a ODS column in a gradient of ammonium acetate buffer (pH 5.0) and acetonitrile. Full-scan mass spectra of the compounds showed molecular ions, and MS-MS spectra showed fragments typical of the particular compounds. LC-ESI-MS allowed an unequivocal differentiation of all muscle relaxants involved. The method was applied in a case of rocuronium and suxamethonium administration in a Caesarian section and in a case of intoxication by pancuronium injection. In both cases, the administered drugs could be detected and identified in the supplied samples.

[Determinations of steroidal muscle relaxants and their metabolites].

Pancuronium, vecuronium and pipecuronium are quaternary ammonium steroidal neuromuscular blocking agents. These drugs are typical nondepolarizing muscle relaxants. The steroidal compounds and/or their metabolites have been determined using mass spectrometry or gas chromatography. In this review, these analytical methods and application of the methods to pharmacokinetics are introduced.

A modification of the kinetic determination of pancuronium bromide based on its inhibitory effect on cholinesterase.

A modification of the existing spectrophotometric kinetic method for the determination of pancuronium bromide (PCBr), based on pooled human serum cholinesterase (ChE, EC 3.1.1.8 acylcholine acylhydrolase) inhibition, was developed. Butyrylthiocholine iodide (concentration 1.667 mmol/L) was used as substrate and determination was performed at pH 7.6. Essential basic kinetic parameters were also determined: Michaelis-Menten's constant KM=0.33 mmol/L, maximal reaction rate Vmax=42.29 micromol/L min, inhibition constant KI=0.34 micromol/L, and IC50=0.235 micromol/L. Linear dependence between the reaction rate and the inhibitor concentration exists in PCBr concentration range 8.29-265.28 nmol/L, which corresponds to the real sample concentrations from 0.166 to 5.306 micromol/L. The method detection limit was established to be 1.86 nmol/L and the quantification limit was 6.18 nmol/L. Precision of the method was tested for three pancuronium concentrations (16.58, 99.48, and 198.96 nmol/L). The relative standard deviation (RSD) was in the range 0.78-5.13%. Accuracy was examined by the standard addition method. The influence of substances usually present in serum and urine on the reaction rate was determined. The method developed was applied for PCBr determination in spiked serum and urine samples and in the urine taken during surgery. The method was proven to have good sensitivity, accuracy, and precision and can be considered suitable for clinical practice.

Cholinesterase inhibition based determination of pancuronium bromide in biological samples.

Pancuronium bromide (PCBr) inhibition effect on enzyme cholinesterase from pooled human serum (Che, EC 3.1.1.8 acylcholine acylhydrolase) was used for development of a spectrophotometric kinetic method for PCBr determination in human serum and urine. Optimal conditions for the basic and inhibitor reactions were established: pH=7.7 and substrate concentration c(benzoylcholine chloride)=1.33 mmol/L. Kinetic parameters were also determined: Michaelis-Menten's constant K(M)=0.40 mmol/L, maximal reaction rate V(max)=52.2 micromol/L min, inhibition constant K(i)=0,56 micromol/L and IC(50)=1.31 micromol/L. Linear dependence between the reaction rate and inhibitor concentration exists in PCBr concentration range 8.20-68.25 nmol/L, which corresponds to the real sample concentrations from 0.328 to 2.730 micromol/L. The method detection and quantification limits were 2.01 nmol/L and 6.67 nmol/L, respectively. Precision of the method was tested for three pancuronium concentrations (10.70, 29.35 and 51.25 nmol/L). Relative standard deviation (RSD) was in the range 0.15-7.45%. Accuracy was examined by standard addition method. Influence of the substances usually present in serum and urine on the reaction rate was tested. The developed method was applied for PCBr content determination in serum model samples, urine model samples and in urine taken during surgery. The method has good sensitivity, accuracy, precision and it is suitable for clinical practice.

Ion-pair extraction method for quantitation of a bisquaternary ammonium compound, pancuronium bromide.

Pancuronium bromide (PCBr), a neuro-muscular blocking agent, was determined quantitatively in aqueous solution by ion-pair extraction. Separate determination of PCBr and degradation products was possible after thin layer chromatography. The procedure was developed by using a theoretical approach. Favorable conditions were calculated from the ion-pair extraction constant. The drug was determined with bromothymol blue at pH 9.0, using one extraction in the direct procedure and 2 successive extractions in the combined elution-extraction process after thin layer chromatography. In the direct method, 0.100 mg PCBr was determined with a reproducibility of +/- 1.0%.

Mass spectrometric assay for determination of pancuronium and vecuronium in biological fluids utilizing the moving belt introduction system.

An assay for the determination of the neuromuscular blocking agents pancuronium bromide and vecuronium bromide in plasma or urine has been developed. This method is based on syringe application of sample extracts to the moving belt surface and single metastable transition monitoring of the elimination of acetic acid from the ion of m/z 543 during chemical ionization. The analysis shows good linearity over three orders of magnitude and is capable of analyzing for the compounds below the 5 ng ml-1 level. The assay has been used in preliminary pharmacokinetic studies of the biological fluids of surgical patients. The utility of the method for simultaneous determination of the deacetylated metabolites of these two drugs has also been investigated.

Quantitation of pancuronium, 3-desacetylpancuronium, vecuronium, 3-desacetylvecuronium, pipecuronium and 3-desacetylpipecuronium in biological fluids by capillary gas chromatography using nitrogen-sensitive detection.

A sensitive and specific capillary gas chromatographic (GC) assay was developed for the quantitation of the quaternary ammonium steroidal neuromuscular blocking drugs pancuronium (PANC), vecuronium (VEC) and pipecuronium (PIP), as well as the metabolites 3-desacetylpancuronium (3-desPANC) and 3-desacetylvecuronium (3-des VEC) in plasma, bile and urine; the putative metabolite 3-desacetylpipecuronium (3-des PIP) was extracted and quantitated only in urine. The procedure employed a single dichloromethane extraction of the iodide ion-pairs of the monoquaternary or bisquaternary ammonium compounds (including internal and external standards) from acidified, ether-washed biological fluid followed by the formation of stable O-tert.-butyldimethylsilyl derivatives at the 3-hydroxy steroidal position of the metabolites. An automated capillary GC system fitted with a nitrogen-sensitive detector and an integrator was then used to analyze and quantitate both parent compounds and their derivatized metabolites. Optimal extraction, derivatization and GC conditions, as well as short-term stability and recoveries of these drugs and metabolites in plasma, are reported. Electron ionization mass spectrometry combined with GC was used to confirm the identities of compounds eluted from the column. The assay demonstrated a 10(3)-fold linear range up to 5000 ng/ml for PANC, VEC, 3-des VEC and PIP, and lower limits of detection with adequate precision of 2 ng/ml for PANC, VEC and PIP, and 4 ng/ml for 3-des VEC; 3-des PANC was linear from 8 to 500 ng/ml while 3-des PIP was linear from 25 to 1000 ng/ml. The precision (coefficient of variation) of the calibration curves for underivatized drugs and their derivatized metabolites over the linear ranges was 2-20% and the reproducibility of the assay over a range of clinical concentrations of these drugs found in human plasma was 5-16% for PANC, 2-4% for VEC and 6-11% for PIP. No interferences were detected in the assay of plasma samples from 106 surgical patients.

Comparación entre el bromuro de pancuronio genérico y el Pavulon®1 / Comparison between generic pancuronium bromide and Pavulon®1

Históricamente se ha planteado el conflicto sobre la eficacia y la seguridad terapéutica entre marcas genéricas y la marca original, lo cual llevó a desarrollar el siguiente estudio. Objetivos: 1) realizar ensayos fisicoquímicos de ampollas que contenían 4 mg/2ml de bromuro de pancuronio, en una marca genérica (G) y en una original (P = Pavulon®), 2) determinar la eficacia y la seguridad terapéutica de ambas drogas, y 3) comparar los resultados entre ambas marcas, tomando como patrón de referencia la marca original. Materiales y métodos: Ensayos fisicoquímicos realizados conforme la Farmacopea Británica 2001 (FB). Eficacia y seguridad terapéutica evaluada mediante un estudio prospectivo, randomizado y doble ciego en cincuenta pacientes ASA I-II a quienes se administró 2 mcg/kg de citrato de fentanilo, 5 mg/kg de tiopental sódico cinco minutos después y 0.1 mg/kg de bromuro de pancuronio. La anestesia se mantuvo con sevoflurano 2 por ciento. Se evaluó el tiempo T1 para alcanzar los valores porcentuales 95,75,25,0 y 25 de recuperación o duración clínica. Comparación: Test de Mann - Whitney, p < 0.05. Resultados: Los ensayos fisicoquímicos para el grupo genérico y el Pavulon® cumplieron con las especificaciones de la FB. En el grupo genérico, los tiempos necesarios para que T1 disminuya hasta 95 y 75 por ciento resultaron respectivamente 33.15 y 48.36 segundos; para que disminuya al 25 por ciento y 0 por ciento, 1.50 Y 2.97 minutos, y la duración clínica fue de 108.99 minutos. En el grupo Pavulon®, el tiempo requerido para T1 = 95 Y 75 por ciento fue de 24.89 y 41.54 segundos respectivamente, mientras que para llegar al 25 y 0 por ciento fueron necesarios 1.34 y 2.71 minutos; la duración clínica en este grupo fue de 111.99 minutos. Conclusiones: Los tiempos evaluados no arrojaron diferencia estadística significativa entre ambas marcas.