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.

LC/MS/MS analysis of quaternary ammonium drugs and herbicides in whole blood.

Quaternary ammonium drugs (atracurium, bretylium, edrophonium, ipratropium, mivacurium, neostigmine, pancuronium and rocuronium) and herbicides (difenzoquat, diquat and paraquat) in human whole blood were analysed by LC/MS/MS with positive electrospray ionisation (ESI), following extraction with Bond Elut LRC-CBA cartridges. Internal standards were benzyldimethylphenylammonium chloride monohydrate and ethyl viologen for drug and herbicide analysis, respectively. Ion-pair chromatography used heptafluorobutyric acid (15 mM)-ammonium formate (20 mM) buffer adjusted to pH 3.30 with formic acid and a linear gradient from 5 to 90% methanol run over 18 min. Recoveries ranged from 79.7 to 105.1%, detection limits were between 3.6 and 20.4 ng/ml and the intra- and inter-day precisions were less than 18.6% at a concentration of 10 ng/ml. The method was applied to a case of accidental paraquat poisoning in which the concentration of paraquat in blood was 0.64 mg/l, which is within the range associated with fatal paraquat poisoning.

Simultaneous determination of pancuronium, vecuronium and their related compounds using LC-ESI-MS.

A simultaneous determination method of quaternary amino steroidal muscle relaxants, pancuronium (PAN), vecuronium (VEC), and 17-monodesacetyl pancuronium (17-OH-PAN), 3,17-bisdesacetyl pancuronium (3,17-OH-PAN), 3-monodesacetyl vecuronium (3-OH-VEC), 3,17-bisdesacetyl vecuronium (3,17-OH-VEC) in human serum was developed using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). The weak cation exchange cartridge was useful for the extraction of these compounds. Under optimized LC-ESI-MS conditions, these compounds were almost fully separated within 6.5 min. Linear responses over the concentration range 0.25-50.0 ng/mL were demonstrated for each compound. The developed method successfully detected VEC, 3-OH-VEC and 3,17-OH-VEC in serum intravenously administered with VEC. The level of 3-OH-VEC was higher than other compounds. This suggested that 3-OH-VEC was useful as a forensic probe in VEC administration.

Potentiation of mivacurium blockade by low dose of pancuronium: a pharmacokinetic study.

BACKGROUND: Mivacurium is potentiated by pancuronium to a much greater extent than other relaxants. In a previous investigation we suggested that this potentiation could be due to the ability of pancuronium to inhibit plasma cholinesterase activity, but we did not measure plasma concentrations of mivacurium. In the current study we performed a pharmacokinetic analysis by measuring the plasma concentration of mivacurium when preceded by administration of a low dose of pancuronium. METHODS: After induction of general anesthesia with propofol and fentanyl and orotracheal intubation, 10 patients (pancuronium-mivacurium group) received 15 microg/kg pancuronium followed 3 min later by 0.1 mg/kg mivacurium, whereas 10 other patients (mivacurium group) received saline followed by 0.13 mg/kg mivacurium 3 min later. Plasma cholinesterase activity was measured before and 3 and 30 min after pancuronium dosing in the pancuronium-mivacurium group and was measured before and after administration of saline in the mivacurium group. Arterial plasma concentrations of mivacurium and its metabolites were measured at 0.5, 1, 1.5, 2, 4, 10, 20, and 30 min after injection. Neuromuscular blockade was assessed by mechanomyography. RESULTS: Plasma cholinesterase activity decreased by 26% in the pancuronium-mivacurium group 3 min after injection of pancuronium (P < 0.01) and returned to baseline values 30 min later; however, no significant variation was observed in the mivacurium group. The clearances of the two most active isomers (Cis-Trans and Trans-Trans) were lower in the pancuronium-mivacurium group (17.6 +/- 5.1, 14.7 +/- 5.3 ml. min-1. kg-1, respectively) than in the mivacurium group (32.4 +/- 20.2, 24.8 +/- 13.5 ml. min-1. kg-1; P < 0.05). CONCLUSIONS: A subparalyzing dose of pancuronium decreased plasma cholinesterase activity and the clearance of the two most active isomers of mivacurium. Pancuronium potentiates mivacurium more than other neuromuscular blocking agents because, in addition to its occupancy of postsynaptic acetylcholine receptors, it slows down the hydrolysis of mivacurium.

[Anesthesia for cesarean section: drug transfer to fetus during anesthesia].

One case of prenatally diagnosed congenital diaphragmatic hernia was reviewed in terms of the anesthetic managements. Concentrations of diazepam, pancuronium and fentanyl were measured in maternal, fetal and umbilical serum. As expectedly, the transition of diazepam through the placenta was large and the concentration of diazepam in the fetal serum was equal to that of maternal serum, but only a small amount of pancuronium was transferred.

Porcine model for studying the passage of non-depolarizing neuromuscular blockers through the blood-brain barrier.

A method has been developed for blood-brain barrier disruption to provide reproducible access to the cerebrospinal fluid of the cerebello-medullary cistern. The technique was used successfully to investigate transfer of pancuronium to the cerebral CSF compartment in pigs. After osmotic disruption of the blood-brain barrier, pancuronium concentrations increased significantly in the cerebrospinal fluid.

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.

Pancuronium and vecuronium pharmacokinetics and pharmacodynamics in younger and elderly adults.

To evaluate the effect of aging on the distribution, metabolism, and neuromuscular junction sensitivity to pancuronium and vecuronium, the authors determined the pharmacokinetics and pharmacodynamics of these drugs in 12 healthy elderly subjects (70-84 yr) and 12 young adults (30-57 yr) during halothane-nitrous oxide anesthesia. Plasma concentrations of the muscle relaxants were determined using a selective ion-monitoring mass spectrometric technique specific for the parent compound. For vecuronium, plasma clearance (3.7 +/- 1.0 and 5.2 +/- 0.8 ml X kg-1 X min-1, respectively), and volume of distribution at steady-state (179 +/- 31 and 244 +/- 38 ml X kg-1, respectively) were lower in the elderly than in young adults; values for distribution half-lives, elimination half-life, and sensitivity of the neuromuscular junction were similar for the two groups. For pancuronium, there were no statistically significant differences between groups for these pharmacokinetic or pharmacodynamic parameters. However, there was a trend toward reduced clearance (20%) and prolonged elimination half-life (16%) in the elderly as compared to the younger patients. The authors conclude that healthy elective surgical patients between the ages of 70 and 84 yr of age do not differ markedly from younger adults in their pharmacokinetic/pharmacodynamic response to vecuronium and pancuronium.

Recovery times following edrophonium and neostigmine reversal of pancuronium, atracurium, and vecuronium steady-state infusions.

The ability of edrophonium and neostigmine to antagonize nondepolarizing neuromuscular blockade produced by steady-state infusions of atracurium, pancuronium, and vecuronium was studied in 71 adult patients anesthetized with nitrous oxide and halothane. Infusion rates of blocking drugs were adjusted so that single twitch depression as measured by the evoked integrated EMG of the hypothenar muscles was kept at 10% of control. Two minutes after the termination of the infusion either edrophonium (0.75 mg/kg) or neostigmine (0.05 mg/kg) was administered. Single twitch depression and train-of-four (T4/T1) fade was recorded during the recovery period. T4/T1 fade ratios observed at 20 min postreversal were 0.80 (atracurium-edrophonium); 0.76 (vecuronium-edrophonium); 0.44 (pancuronium-edrophonium); 0.95 (atracurium-neostigmine); 0.89 (vecuronium-neostigmine); and 0.68 (pancuronium-neostigmine). Under conditions of this study neostigmine produced more rapid and complete recovery than did edrophonium. Although edrophonium produced adequate antagonism of atracurium if 20-30 min were allowed to elapse, edrophonium reversal of pancuronium was rarely acceptable even at 30 min. Increasing the dose of edrophonium to 1.0 mg/kg produced single twitch values of 0.90 at 5 min postreversal but did not increase the rate of recovery of the train-of-four fade ratio. Neostigmine reversal of pancuronium, on the other hand, generally produced T4/T1 ratios of greater than 0.70 in 20-30 min. Although the pattern of recovery seen after reversal of vecuronium was in general quite similar to that seen after atracurium, two patients in the vecuronium-edrophonium group showed delayed recovery and also failed to respond significantly to subsequent doses of neostigmine.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics and pharmacodynamics of vecuronium and pancuronium in anesthetized children.

The pharmacokinetics and pharmacodynamics of vecuronium and pancuronium were determined in 12 children (3-6 yr) undergoing minor surgery under 60% nitrous oxide, 1 MAC halothane anesthesia. When the level of anesthesia and the electromyograph (EMG) recording of the adductor pollicis were stable, an intravenous bolus of vecuronium (100 micrograms/kg) or pancuronium (100 micrograms/kg) was administered. Plasma concentrations of the two muscle relaxants were determined for 6 hr after the administration by means of a fluorimetric assay followed by a thin layer chromatography. Plasma concentrations of vecuronium and pancuronium declined biexponentially in children and no metabolites could be detected in plasma. The elimination half-lives of vecuronium and pancuronium did not differ significantly. The volume of distribution at steady state (Vdss) was greater (P less than 0.05) after vecuronium (320 +/- 181 ml/kg; mean +/- SD) than after pancuronium (203 +/- 36 ml/kg). Plasma clearance of vecuronium (2.8 +/- 0.9 ml X min-1 X kg-1) was greater than that of pancuronium (1.7 +/- 0.2 ml X min-1 X kg-1; P less than 0.05). Plasma concentrations measured at 10%, 50%, or 90% recovery of the EMG response did not differ significantly for vecuronium and pancuronium. Thus the shorter duration of action of vecuronium is probably due to its greater apparent volume of distribution, as well as to its higher plasma clearance. Thus although the elimination half-lives are comparable, the plasma disappearance of vecuronium is more rapid than that of pancuronium.

Quantitative estimation of quaternary ammonium neuromuscular blocking agents in serum by direct insertion probe chemical ionization mass spectrometry.

A new method based on selected ion monitoring chemical ionization mass spectrometry was developed to measure the quaternary ammonium neuromuscular blocking agents, pancuronium and vecuronium, in serum. An ion-pair extraction procedure is utilized to separate the compounds of interest from biological fluids. The intensities of the ion currents produced by the bisamines formed from the drugs and the corresponding deuterated internal standards through thermolytic dequaternization are monitored. The assay shows good linearity over the range of 1-500 ng/ml. This assay has been utilized in a variety of clinical pharmacokinetic studies involving surgical pediatric, geriatric and obstetric patients requiring anesthesia.

Neuromuscular blocking effects of atracurium, vecuronium and pancuronium during bolus and infusion administration.

The potencies of atracurium, vecuronium and pancuronium were compared using bolus injections and continuous infusions. The sizes of the bolus injections were based on previously determined cumulative dose-response relationships. Dose requirements for 90% and 50% sustained blockade were estimated by use of continuous infusion, and the corresponding plasma concentrations were measured for vecuronium and pancuronium. The effect of single bolus injections correlated well with the cumulative dose-responses, confirming relative potencies for atracurium, vecuronium and pancuronium of approximately 1:5:4. The maintenance doses (microgram kg-1 h-1) for 90% blockade were: atracurium 382.8, vecuronium 101.9, and pancuronium 36.9, making the relative dose requirements 10.4:2.8:1. The same dose ratio was found for atracurium and vecuronium at 50% blockade. This required about 60% of the doses needed for maintenance of 90% response. The relative potency of vecuronium and pancuronium in plasma was 1.1:1. The 25-75% recovery index was significantly shorter for vecuronium than for atracurium.

Disposition of vecuronium bromide in the cat.

The disposition of vecuronium bromide has been investigated in six normal cats (group I) and in six cats with ligated renal pedicles (group II). A combined fluorimetric and chromatographic technique was used to determine the concentrations of vecuronium and its metabolites in biological material. After i.v. injection of 0.6 mg kg-1, vecuronium disappeared rapidly from the plasma of the normal cat. Concentrations decreased bi-exponentially with half-lives of 4.6 and 31 min, respectively. The steady state volume of distribution was 0.23 litre kg-1 and the clearance 11 ml min-1 kg-1. Seventy percent of an i.v. dose of vecuronium (or its metabolites) was recovered: 15% in the urine, 40% in the bile and 15% in the liver. Only 3.8% of this consisted of the 3-hydroxy metabolite. There were no significant differences in pharmacokinetic data or in the amounts of vecuronium and its metabolites recovered in cats with ligated renal pedicles. The 15% of vecuronium normally excreted by the kidney was compensated for by increased hepatic and biliary concentration of vecuronium.

Pharmacokinetics and pharmacodynamics of vecuronium (ORG NC 45) in patients with cirrhosis.

To evaluate the effect of liver cirrhosis on the pharmacokinetics and the pharmacodynamics of vecuronium, 12 patients with cirrhosis, aged (mean +/- SD) 52 +/- 12 yr, and 14 control patients, 42 +/- 15 yr, undergoing elective surgery under general anesthesia were studied. The simultaneous time courses of the plasma concentration of vecuronium and of the neuromuscular blockade were studied after the administration of a bolus dose of 0.2 mg X kg-1. Vecuronium plasma concentration declined biexponentially in both groups. Vecuronium plasma clearance was reduced significantly (P less than 0.01) from 4.26 +/- 1.38 ml X min-1 X kg-1 in the controls to 2.73 +/- 1.19 ml X min-1 X kg-1 in the patients with cirrhosis. The elimination half-life was 58 +/- 19 min in the controls and was prolonged significantly to 84 +/- 23 min (P less than 0.01) in the patients with cirrhosis. The total apparent volume of distribution was unchanged in patients with cirrhosis (0.253 +/- 0.086 1 X kg-1 vs. 0.246 +/- 0.092 1 X kg-1 in the controls). Cirrhosis caused a prolongation of the neuromuscular blockade induced by vecuronium: the duration of effect from injection to 50% recovery of the twitch height was prolonged by 100% (P less than 0.01) from 62 +/- 16 min in the controls to 130 +/- 52 min in patients with cirrhosis. The recovery rate (TH 25-75) also was prolonged (P less than 0.05) from 21 +/- 7 min in the controls to 44 +/- 18 min in patients with cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Vecuronium in patients with and without renal failure.

Fifteen patients with and ten patients without renal failure (RF) were given vecuronium as the sole muscle relaxant during anaesthesia. RF patients were divided into two subgroups according to the daily diuresis (RF I, below 0.5 l/d; RF II, over 0.5 l/d). Vecuronium was given in small doses until the electromyographic twitch response showed 90% relaxation. The results showed great individual variations, and there were no statistically significant differences between the study groups in the parameters studied (ED90 dose, total consumption of the drug in mg kg-1 min-1, vecuronium plasma concentrations, twitch response) during induction and anaesthesia. After reversal of relaxation, the twitch response recovered more slowly in the RF I group than in the others (P less than 0.05). No complications occurred and it is confirmed that it is safe to use vecuronium as a muscle relaxant in patients with RF.

Vecuronium kinetics and dynamics in anesthetized infants and children.

Vecuronium kinetics and dynamics were determined in five infants (3 to 11 months old) and five children (1 to 5 years old) during anesthesia with 70% nitrous oxide and 0.9 MAC halothane. Vecuronium was infused intravenously at a rate of 2.5 micrograms/kg/min while twitch tension of the adductor pollicis muscle was recorded and venous blood samples were drawn for determination of vecuronium concentrations by mass spectrometry. The elimination t1/2 was determined by linear regression of the log postdistribution concentration-time data; these values and noncompartmental techniques were used to calculate total plasma clearance (Cl), volume of distribution at steady state (Vdss), and mean residence time. The steady-state plasma concentration resulting in 50% depression of twitch tension (Cpss50) was determined by an effect compartment and a sigmoid concentration vs. paralysis model. Vdss was larger in infants (357 +/- 70 ml/kg; mean +/- SD) than in children (204 +/- 116 ml/kg), and Cl was of the same order for infants and children (5.6 +/- 1.0 and 5.9 +/- 2.4 ml/kg/min). Mean residence time was longer in infants (66.3 +/- 22.9 minutes) than in children (34.3 +/- 8.0 minutes). Cpss50 was lower in infants (57 +/- 18 ng/ml) than in children (110 +/- 28 ng/ml). The quantity of vecuronium in the body at steady state at 50% depression of twitch tension (Vdss X Cpss50) was similar in infants and children (21.2 +/- 9.9 and 19.0 +/- 3.3 micrograms/kg). During comparable nitrous oxide-halothane anesthesia, age-related changes in Vdss, Cl, and Cpss50 were much like those found for d-tubocurarine.(ABSTRACT TRUNCATED AT 250 WORDS)