Structural elucidation of amino amide-type local anesthetic drugs and their main metabolites in urine by LC-MS after derivatization and its application for differentiation between positional isomers of prilocaine.

The demand for clinical toxicology analytical methods for identifying drugs of abuse and medicinal drugs is steadily increasing. Structural elucidation of amino amide-type local anesthetic drugs and their main metabolites by GC-EI-MS and LC-ESI-MS/MS is of great analytical challenge. These compounds exhibit only/mostly fragments/product ions representing the amine-containing residue, while the aromatic amide moiety remains unidentified. This task becomes even more complicated when discrimination between positional isomers of such compounds is required. Here, we report the development of a derivatization procedure for the differentiation and structural elucidation of a mixture of local anesthetic drugs and their metabolites that possess tertiary and secondary amines in water and urine. A method based on two sequential "in-vial" instantaneous derivatization processes at ambient temperature followed by LC-ESI-MS/MS analysis was developed. 2,2,2-Trichloro-1,1-dimethylethyl chloroformate (TCDMECF) was utilized to selectively convert the secondary amines into their carbamate derivatives, followed by hydrogen peroxide addition to produce the corresponding tertiary amine oxides. The resulting derivatives exhibited rich fragmentation patterns, enabling improved structural elucidation of the original compounds. The developed method was successfully applied to the differentiation and structural elucidation of prilocaine and its four positional isomers, which all possess similar GC and LC retention times and four of them exhibit almost identical EI-MS and ESI-MS/MS spectra, enabling their structural elucidation in a single LC-ESI-MS/MS analysis. The developed technique is fast and simple and enables discrimination between isomers based on different diagnostic ions/fragmentation patterns.

Polymer-spray mass spectrometric detection and quantitation of hydrophilic compounds and some narcotics.

RATIONALE: High-throughput screening of biofluids is essential in monitoring concentration of a variety of drugs to determine their efficacy and toxicity. Organosiloxane polymers prepared by sol-gel chemistry as sample supports, and electrospray ionization emitters in a single material and as an alternative to paper substrates, is described in this study. METHODS: Hydrophobic drugs and hydrophilic streptomycin were analyzed by polymer-spray mass spectrometry with an LTQ-Orbitrap mass spectrometer. Drug samples in urine (1-2 µL) were deposited on an OSX polymer, allowed to dry, then electrosprayed from the polymer tip into the mass spectrometer without sample pretreatment. The OSX polymers, whose polarity and porosity can be controlled, were prepared by sol-gel chemistry where methyl-substituted alkoxysilanes were hydrolyzed in the presence of a pore template and an acid catalyst. RESULTS: Five nanograms each of seven narcotic drugs were detected in <1 min (relative standard deviation (RSD) of response <1% for each drug). Calibration curves of cocaine and streptomycin in urine were used to establish the performance of the polymer. For sample 1 (n = 2), the mean recovery for cocaine was 81% with paper and 90% with polymer. Streptomycin is detected with polymer, not with paper; for samples 1 and 2 (n = 3), mean recovery was 97% and 95%, respectively. CONCLUSIONS: Organosiloxane polymers achieve more sensitive analysis than paper, allowing for more accurate quantitation of both hydrophobic and hydrophilic drug compounds. The ability to tailor the polymer polarity and porosity allows for the synthesis of a wide range of polymers, and thus opens many possibilities for further development and applications.

Direct fluorescence anisotropy assay for cocaine using tetramethylrhodamine-labeled aptamer.

Development of simple, sensitive, and rapid method for cocaine detection is important in medicine and drug abuse monitoring. Taking advantage of fluorescence anisotropy and aptamer, this study reports a direct fluorescence anisotropy (FA) assay for cocaine by employing an aptamer probe with tetramethylrhodamine (TMR) labeled on a specific position. The binding of cocaine and the aptamer causes a structure change of the TMR-labeled aptamer, leading to changes of the interaction between labeled TMR and adjacent G bases in aptamer sequence, so FA of TMR varies with increasing of cocaine. After screening different labeling positions of the aptamer, including thymine (T) bases and terminals of the aptamer, we obtained a favorable aptamer probe with TMR labeled on the 25th base T in the sequence, which exhibited sensitive and significant FA-decreasing responses upon cocaine. Under optimized assay conditions, this TMR-labeled aptamer allowed for direct FA detection of cocaine as low as 5 µM. The maximum FA change reached about 0.086. This FA method also enabled the detection of cocaine spiked in diluted serum and urine samples, showing potential for applications. Graphical Abstract The binding of cocaine to the TMR-labeled aptamer causes conformation change and alteration of the intramolecular interaction between TMR and bases of aptamer, leading to variance of fluorescence anisotropy (FA) of TMR, so direct FA analyis of cocaine is achieved.

An aptamer folding-based sensory platform decorated with nanoparticles for simple cocaine testing.

The consumption of illicit drugs such as cannabis, cocaine, and amphetamines is still a major health and social problem, creating an abuse in adults especially. Novel techniques which estimate the drug of abuse are needed for the detection of newly revealed psychoactive drugs. Herein, we have constructed a combinatorial platform by using quantum dots (QDs) and gold nanoparticles (AuNPs) as well as a functional aptamer which selectively recognizes cocaine and its metabolite benzoylecgonine (BE). We have called it an aptamer folding-based sensory device (AFSD). For the fabrication of AFSD, QDs were initially immobilized onto the poly-L-lysine coated µ-well surfaces. Then, the AuNP-aptamer conjugates were bound to the QDs. The addition of cocaine or BE caused a change in the aptamer structure which induced the close interaction of AuNPs with the QDs. Hence, quenching of the fluorescence of QDs was observed depending on the analyte amount. The linearity of cocaine and BE was 1.0-10 nM and 1.0-25 µM, respectively. Moreover, the limits of detection for cocaine and BE were calculated as 0.138 nM and 1.66 µM. The selectivity was tested by using different interfering substances (methamphetamine, bovine serum albumin, codeine, and 3-acetamidophenol). To investigate the use of AFSD in artificial urine matrix, cocaine/BE spiked samples were applied. Also, confirmatory analyses by using high performance liquid chromatography were performed. It is shown that AFSD has a good potential for testing the cocaine abuse and can be easily adapted for detection of various addictive drugs by changing the aptamer according to desired analytes. Copyright © 2016 John Wiley & Sons, Ltd.

Resonance Rayleigh scattering technique as a detection method for the RP-HPLC determination of local anaesthetics in human urine.

A highly selective and sensitive method of reversed phase high-performance liquid chromatography (RP-HPLC) coupled with resonance Rayleigh scattering (RRS) was developed for the determination of procaine, bupivacaine and tetracaine. Separation of three local anaesthetics was achieved at 35 °C on a C18 column. The mobile phase was 30: 70 (v/v) acetonitrile/triethylamine-phosphoric acid buffer (pH 2.9) at flow rate of 0.3 mL/min. The RRS detection was conducted by taking advantage of the strong RRS enhancement of the local anaesthetics with erythrosine reaction in an acidic medium. Under optimum conditions, the limit of detection (S/N = 3) values were in the range of 2.4-11.2 ng/mL. Recoveries from spiked human urine samples were 95.8%-104.5%. The proposed method applied to the determination of local anaesthetics in human urine achieved satisfactory results. In addition, the mechanism of the reaction is fully discussed. Copyright © 2016 John Wiley & Sons, Ltd.

On-line preconcentration strategy for the simultaneous quantification of three local anesthetics in human urine using CZE.

The simultaneous determination of usually employed anesthetics (procaine, lidocaine, and bupivacaine) has been developed and validated using CE with ultraviolet detection at 212 nm. The separation of these three drugs has been achieved in less than 7 min, using a temperature of 25ºC and 25 kV, with a 150 mM citrate buffer (pH 2.5) as BGE. Field-amplified sample injection (FASI) has been used for on-line sample preconcentration. Ultrapure water and ACN 50/50 (v/v) mixture gave the greatest enhancement factor when it was employed as an injection solvent. Injection voltage and time were optimized, being 13 kV and 13 s, the optimum values, respectively. To avoid the possible irreproducibility associated with the electrokinetic injection, an internal standard such as tetracaine, was employed. The instrumental detection limits (LOD S/N = 3) for the compounds ranged between 2.6 and 7.0 µg L(-1) and the quantitation limits (LOQ S/N = 10) between 37.8 and 55.9 µg L(-1) . The detection limits obtained in real human urine samples ranged between 55.2 and 83.6 µg L(-1) and the quantitation limits between 196.0 and 276.0 µg L(-1) . The proposed method has demonstrated its applicability to the analysis of these local anesthetics in urine samples without any pretreatment, allowing the rapid determination of these target analytes.

Investigations into distribution of lidocaine in human autopsy material.

With screening methods in the legal medicine drugs were often detected in autopsy material. In this study the antiarrhythmic and the local anesthetic drug lidocaine could be proved in fifty-one cases and determined in different autopsy materials. For the first time the comparison of so many distribution patterns of lidocaine in human compartments was possible. A liquid-liquid extraction procedure, a standard addition method and LC/MS/MS were used for analytics. The measured concentrations in blood were in the therapeutic range or lower. The time between lidocaine application and death was given in twenty-nine cases. These data were very helpful to estimate and interpret the distribution process of lidocaine between application and death. This time exerted a crucial influence on the distribution of lidocaine in the compartments. Most of the intravenous applicated lidocaine was found in heart blood after a very short time of distribution. Afterwards the highest concentrations were measured in brain. Later the highest concentration was found in the kidney samples or in urine. If the time between lidocaine application and death is known, the results of this study can be used to deepen the knowledge of its pharmacokinetics. If this time is unknown, the circumstances and the causes of death can be better explained.

A competitive strategy based on cucurbit[7]uril supramolecular interaction for simple and sensitive detection of dibucaine.

In this work, the competitive interaction between dibucaine and three fluorescent probes (i.e., berberine, palmatine, and coptisine) for occupancy of the cucurbit[7]uril (CB[7]) cavity was studied by fluorescence spectra, UV-visible absorption spectra, (1)H NMR spectra, and theoretical calculations in acidic aqueous solution. Based on the fluorescence enhancement of berberine, palmatine, and coptisine upon binding with CB[7], respectively, a series of fluorescence detection methods for dibucaine were proposed. At the optimized conditions, the fluorescence intensity of berberine-CB[7], palmatine-CB[7], and coptisine-CB[7] complexes showed negative correlation to the concentration of dibucaine, which led to a series of simple and sensitive fluorescence methods for the determination of dibucaine for the first time. Linear ranges obtained in the detection of the dibucaine were 0.018-3.34 µmol L(-1), 0.032-4.47 µmol L(-1), and 0.079-4.42 µmol L(-1) with detection limits of 6.0 nmol L(-1), 12.0 nmol L(-1), and 25.0 nmol L(-1), respectively. Moreover, the proposed method was successfully applied for the determination of the drug in biological fluids. The competitive mode based on CB[7] superstructure provided a promising assay strategy for fluorescence detection in various potential applications.

Use of lidocaine in endotracheal intubation. Blood and urine concentrations in patients and deceased after unsuccessful resuscitation.

In toxicological analysis of postmortem samples the local anesthetic lidocaine is often identified. In most cases, lidocaine levels result from its use as aid in endotracheal intubation. The range of the drug's concentration in blood and urine was studied under controlled conditions from a cohort of cardiac surgery patients (n=35). Plasma concentrations 1 h after exposure to lidocaine in the range of the recommended 81 mg coating the endotracheal tube were less than 0.2 mg/l, its metabolite monoethylglycinxylidide (MEGX) less than 0.05 mg/l (median ratio 0.18, range 0.03-1.23). Also the concentrations of lidocaine and MEGX in urine samples were low (less than 1.2 and 0.1 mg/l, respectively) with MEGX/lidocaine ratios of 0.11 (median, range up to 1.2). These data were compared with results obtained by analyzing postmortem blood and urine samples of 18 deceased with a documented cardiopulmonary resuscitation attempt prior to death. Blood concentrations were in the same range (lidocaine median 0.07, range 0.02-1.07 mg/l; MEGX median 0.01, range <0.001-0.044 mg/l); besides low lidocaine concentrations in urine. MEGX was detected only in 2 out of 9 urine samples. The results of the present study confirm that lidocaine is absorbed in the trachea from the endotracheal tube coated with lidocaine containing gel. Postmortem quantitative results can be explained on the basis of the data obtained in the controlled study.

Molecularly imprinted polymer in microextraction by packed sorbent for the simultaneous determination of local anesthetics: lidocaine, ropivacaine, mepivacaine and bupivacaine in plasma and urine samples.

This study presents the use of molecularly imprinted polymer (MIP) as packing material for microextraction by packed syringe (MEPS) to achieve higher extraction selectivity. Pentycaine was used as template for MIP. Development and validation of the determination of lidocaine, ropivacaine, mepivacaine and bupivacaine in human plasma and urine samples utilizing MIP-MEPS and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were carried out. The MEPS MIP-cartridge could be used for 100 extractions before it was discarded. The extraction recovery ranged from 60 to 80%. The correlation coefficients values were >0.999 for all assays using lidocaine, ropivacaine, mepivacaine and bupivacaine in the calibration range 5-2000 nmol/L. The accuracy of the studied compounds, given as a percentage variation from the nominal concentration values, ranged from -4.9 to 8.4% using plasma and urine samples. The between-batch precision, given as the relative standard deviation, at three different concentrations (quality control samples) was ranged from -4.7 to 14.0% and from 1.8 to 12.7% in plasma and urine, respectively. The lower limit of quantification and limit of detection of the studied substances were 5.0 and 1.0 nm, respectively.

Utility of cocaine drug screens to predict safe delivery of general anesthesia for elective surgical patients.

Cocaine has been associated with acute hemodynamic changes, causing anesthesia providers to be concerned about adverse hemodynamic events during general anesthesia. We sought to determine if there were differences in the prevalence of adverse hemodynamic events, and if hemodynamic instability could be predicted in cocaine-positive patients undergoing general anesthesia for elective surgery. A retrospective cohort study was conducted in 300 (150 cocaine-positive, 150 cocaine-negative) consecutive adults with similar general anesthesia plans who were hemodynamically normal at baseline. Subjects were excluded if they were not alert at baseline, or if they required more than 1 surgical procedure. Slightly more than 50% of subjects were female, but cocaine-positive subjects were significantly more likely to be male (chi2 = 5.9; P = .02). Baseline systolic pressure (P = .001; mean difference, 6.5 mm Hg; 95% confidence interval [CI], 2.7-70.2), mean arterial pressure (P = .04; mean difference, 2.9 mm Hg; 95% CI, 1.0-5.7), and heart rate (P = .02; mean difference, 3.3/min; 95% CI, 0.46-6.2) were significantly higher, but not clinically important in the cocaine-positive cohort. Our study demonstrates that use of drug screen results alone is insufficient to predict the safe administration of general anesthesia in patients undergoing elective surgeries.

Determination of tetracaine hydrochloride by fluorescence quenching method with some aromatic amino acids as probes.

A novel fluorescence quenching method for the determination of tetracaine hydrochloride (TA·HCl) concentration with some aromatic amino acids as fluorescence probe has been developed. In pH 6.3 acidic medium, tryptophane (Trp), tyrosine (Tyr) or phenylalanine (Phe) can react with tetracaine hydrochloride to form an ion-association complex by electrostatic attraction, aromatic stacking interaction and Van der Waals' force, which lead to fluorescence quenching of above amino acids. The maximum fluorescence excitation and emission wavelengths of them are located at 278, 274, 258 nm and 354, 306, 285 nm, respectively. The relative fluorescence intensity (F (0)/F) is proportional to the TA·HCl concentration in certain range. The linear ranges and detection limits are 1.2-5.0 µg/mL and 0.37 µg/mL for Tyr-TA·HCl system, 1.3-6.0 µg/mL and 0.38 µg/mL for Trp-TA·HCl system, and 1.4-6.0 µg/mL and 0.41 µg/mL for Phe-TA·HCl system. The optimum reaction conditions, influencing factors and the effect of coexisting substances are investigated. And the results show the method has a good selectivity. Judging from the effect of temperature, the Stern-Volmer plots and fluorescence lifetime determination, the quenching of fluorescence of amino acids by TA·HCl is a static quenching process.

Chromatographic analysis of local anesthetics in biological samples.

This paper reviews gas and liquid chromatographic methods for screening, identification and quantification of local anesthetics and/or their metabolites in biological samples. Basic information about sample preparation, separation, detection, and quantification of each procedure is summarised. The pros and cons of the various procedures are critically discussed.

[Decomposition kinetics of bupivacaine in biological specimens].

OBJECTIVE: To study on the decomposition kinetics of bupivacaine in brain, blood and urine, which were collected from dogs executed by bupivacaine and stored in different conditions. METHODS: Dogs were given arachnoid cavity anesthesia with bupivacaine. Then the brain, blood and urine were collected and divided equally to three groups stored in 20, 4 and -20 degrees C respectively. The concentrations of bupivacaine at different days were determined by the GC. The equation and half-time period of decomposition kinetics were imitated and calculated with WinNolin program. RESULTS: The decomposition kinetics of bupivacaine in the dogs' brain, blood and urine were fit to the first order kinetics. The common equation was lgC = lgCo-kt/2.303 and k was the decomposition constant of first order reaction. CONCLUSION: Bupivacaine in the brain, blood and urine specimens were found to be decomposed at various environments for storage. The higher temperature for storage, the faster of decomposition reaction.

Analysis of drugs of abuse in biofluids by low temperature plasma (LTP) ionization mass spectrometry.

Low temperature plasma (LTP) ionization is an ambient plasma ionization method that permits the direct mass analysis of samples in their native atmospheric environment with little or no sample preparation. In this work, the low temperature plasma probe is used in the direct and rapid mass spectrometric analysis of aqueous phase samples including biofluids (saliva, urine, and hair extract). A detailed trace qualitative examination of 14 drugs of abuse has been performed. The relative standard deviation on average was approximately 16% for the LTP analysis of the drugs of abuse standards. Eleven of the fourteen drugs of abuse were detected in the low ng mL(-1) (3 pg absolute detection) to the mid microg mL(-1) (approximately 30 ng absolute detection) concentration range. One drug, cannabidiol, could not be detected until supplemental heating of the substrate was incorporated into the experimental protocol. The addition of supplemental heating improved the detection limits by at least an order of magnitude to approximately 0.5 ng mL(-1) to 0.5 microg mL(-1) (1.5 pg-1.5 ng absolute) for twelve of the fourteen drugs of abuse, so extending the linear dynamic range which for most analytes was four orders of magnitude. Quantitative capabilities were evaluated using the particular example of benzoylecgonine in urine by employing a deuterated internal standard. Matrix effects observed during the analysis of the drugs in complex biological fluids are also discussed. In addition, low temperature plasma ionization was applied to the examination of real (not spiked) biological samples and these results were confirmed using standard LC/MS methodology. The main advantages observed for this ambient desorption/ionization technique include the capabilities for direct analysis of liquid surfaces for in situ detection and the remarkable sensitivity in the examination of the drugs of abuse investigated here. The disadvantages of the method include the modest quantitative accuracy making LTP most useful as a rapid but semi-quantitative screening method.

Decomposition kinetics of bupivacaine in biological specimens / 法医学杂志

OBJECTIVE@#To study on the decomposition kinetics of bupivacaine in brain, blood and urine, which were collected from dogs executed by bupivacaine and stored in different conditions.@*METHODS@#Dogs were given arachnoid cavity anesthesia with bupivacaine. Then the brain, blood and urine were collected and divided equally to three groups stored in 20, 4 and -20 degrees C respectively. The concentrations of bupivacaine at different days were determined by the GC. The equation and half-time period of decomposition kinetics were imitated and calculated with WinNolin program.@*RESULTS@#The decomposition kinetics of bupivacaine in the dogs' brain, blood and urine were fit to the first order kinetics. The common equation was lgC = lgCo-kt/2.303 and k was the decomposition constant of first order reaction.@*CONCLUSION@#Bupivacaine in the brain, blood and urine specimens were found to be decomposed at various environments for storage. The higher temperature for storage, the faster of decomposition reaction.

Cocaine detection in postmortem samples following therapeutic administration.

Cocaine is one of the most widely abused drugs and one that is frequently encountered in forensic toxicology laboratories. Most often, the detection of cocaine would lead toxicologists and forensic pathologists to believe that the drug was used illicitly; however, cocaine is an effective local anesthetic and vasoconstrictor and is used clinically in surgeries of the eye, ear, nose, and throat. Therefore, it is important to note that the presence of cocaine and its metabolites in forensic samples cannot always be attributed to abuse and that a thorough investigation and review of medical records is warranted before an informed conclusion can be made. In this case report, a 54-year-old male died three days after an altercation in which he suffered multiple injuries. In addition to natural disease and injuries documented at autopsy, cocaine and its metabolites were detected in the decedent's urine, and a review of surgical records showed that earlier on the day of death, he was administered cocaine clinically during a procedure to repair nasal bone fractures. If not for this comprehensive investigation and review of surgical records, the assumption of cocaine abuse might have otherwise been made and the cause and manner of death incorrectly established.

[Detection of certain local anesthetics in biological fluids by chemo-toxicological analysis].

Analytical procedures for the detection of certain local anesthetics (including lidocaine, trimecaine, articaine, and anilocaine) in blood and urine are described with special reference to their application in chemotoxicological studies. The description is focused on the methods for isolation of the assay preparations from biological fluids and their identification with the help of up-to-date chromatographic techniques, such as thin layer chromatography, high performance liquid chromatography, and gas-liquid chromatography.

Acute toxicity evaluation of proliferol: a dose-escalating, placebo-controlled study in swine.

Prolotherapy is one of the many treatments available for chronic musculoskeletal disorders. A commonly used drug contains dextrose 12.5%, glycerin 12.5%, phenol 1.0%, and lidocaine hydrochloride 0.25% in aqueous solution (recently termed Proliferol). For chronic low back pain, this is injected into lumbosacral ligaments to stimulate connective tissue repair. Despite generally positive clinical results, the toxicity of this drug is not well characterized and was assessed in 48 (24 male, 24 female) Yucatan miniature swine randomly assigned to low (1x), medium (5x), or high (10x) dose or saline placebo. Outcomes included clinical observations, clinical chemistry, hematology, coagulation, urinalysis, toxicokinetics, and full gross and microscopic histopathology after 24 hours or 14 days. Findings attributable to Proliferol after 24 hours included dose-response elevations in alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and creatine kinase, which returned to normal after 14 days. There were no remarkable findings in hematology, coagulation, or urinalysis. Urine concentrations of lidocaine and phenol both peaked after 8 hours. Histopathology findings after 24 hours included hemorrhage, inflammation, necrosis, and vascular changes in the ligaments and adjacent soft tissues at the sites of injection. After 14 days, there was evidence of repair under way, with fibrosis and skeletal muscle regeneration at the injection sites.

Capillary zone electrophoresis with diode-array detection for analysis of local anaesthetics and opium alkaloids in urine samples.

The present study describes the simultaneous determination of four drugs, two local anaesthetics (lidocaine and bupivacaine) and two opium alkaloids (noscapine and papaverine) by capillary zone electrophoresis (CZE) with solid-phase extraction (SPE) procedure using Oasis HLB cartridges. Their recoveries ranged from 81 to 107% at the target concentrations of 2.0, 5.0 and 8.0 microgmL(-1) in spiked urine samples. Coefficients of variation of the recoveries ranged from 2.1 to 11.3% at these concentrations. The quantitation limits of the method were approximately 300 ngmL(-1) for the different compounds studied. The assay is very specific for these compounds and requires a short sample preparation procedure prior to the electrophoretic analysis.