Simultaneous determination of procaine, lidocaine, ropivacaine, tetracaine and bupivacaine in human plasma by high-performance liquid chromatography

Cupric ion coordination-mediated molecularly imprinted electrochemical sensor for the recognition and ratiometric detection of lidocaine

Molecularly imprinted polymers (MIPs) have been widely used as artificial recognition elements in sensing applications. However, their electrochemical sensing performance is generally hampered by limited affinity and uncontrolled condition change. In this work, a novel MIP electrochemical sensor based on metal coordination interaction was prepared and used for the recognition and ratiometric detection of lidocaine (LC). The sensor was constructed by electrodepositing Cu-coordinated MIP on biomass carbon modified glassy carbon electrode. Herein, Cu2+ ions acted as anchor for the immobilization of LC during the synthesis process, enabling the orderly formation of molecular recognition sites. Reversely, the metal coordination between Cu2+ ions and LC molecules facilitated the recognition of LC. Moreover, the doped cupric ions in the polymer film could provide a reference signal for subsequent ratiometric strategy. Thus the resulting sensor exhibited high selectivity, sensitivity, satisfactory reproducibility, and anti-interference ability. Under the selected conditions, the peak current ratio of LC and cupric ion was linear to LC concentration in the range of 0.008-2.5 μmol L-1 (R2 = 0.9951), and the limit of detection was 1.9 nmol L-1 (S/N = 3). The practical feasibility of the sensor was evaluated by detecting human serum and pharmaceutical samples, and satisfactory outcomes were obtained.

Eco-friendly four spectrophotometric approaches for the simultaneous determination of the recently FDA-approved combination, bupivacaine and meloxicam in pharmaceutical dosage forms

In this study, bupivacaine (BUP) and meloxicam (MLX) were simultaneously assayed in their co-formulated ampoules without interference using four affordable, sensitive, and eco-friendly spectrophotometric methods. The assay of MLX at 359.3 nm over the concentration range of 1.0-15.0 µg/mL was accomplished using a direct UV-spectrophotometric method (Method I) without interference from BUP. However, there was a significant overlap between the spectra of BUP and MLX, making it difficult to determine BUP directly from the UV spectrum. Therefore, various UV-based techniques, including second derivative spectrophotometry (Method II), ratio subtraction method (Method III), and absorption factor method (Method IV), were used to determine BUP over the concentration range of 5.0-80.0 µg/mL. The proposed methods could simultaneously determine the studied drugs with a challenging ratio of 33.3:1.0 (BUP: MLX), which increases the importance of the current study. The proposed methods were applied to estimate the studied drugs in commercial ampoules with high % recoveries and low %RSD values. The excellent eco-friendliness of the developed methods was demonstrated using GAPI and AGREE metrics. The developed methods were validated according to ICHQ2(R2) guidelines. The proposed methods can be better suited for the routine analysis of BUP and MLX in their fixed-dose combination with high selectivity.

LC-MS/MS method for dual-ligand peptide-drug CBP-1018 and its deconjugated payload MMAE including sample stabilization strategy for its MC-Val-Cit-PABC linker

Recently, peptide-drug conjugate (PDC) has become the most promising conjugated drug for tumor therapy after antibody-drug conjugate due to stronger tumor penetration capacity and lower immunogenicity. CBP-1018 was a PDC with dual-ligand conjugated to MMAE via a cleavable linker (MC-Val-Cit-PABC) that can be lysed by cathepsins B. In this study, two specific LC-MS/MS methods were developed and validated for the determination of CBP-1018 and its metabolite MMAE in human plasma. To prevent the cleavable MC-Val-Cit-PABC linker from degradation, a protease inhibitor (cOmplete solution) was added to the pre-cooled vacuum tubes and the separated plasma samples. The assays involved the pretreatment of CBP-1018 by protein precipitation with H2O-ACN (1:9, v/v) and the extraction of MMAE by liquid-liquid extraction with ethyl acetate under alkaline condition to eliminate the interference of CBP-1018 on MMAE. The two analytes showed good linearities over the calibration ranges (R2 ≥ 9980). Both accuracy and precision met the acceptance criteria. The validated methods were successfully applied to the phase I dose-escalation study of CBP-1018 injection in Chinese patients with solid tumors to evaluate the pharmacokinetic properties of CBP-1018 and MMAE. The results showed that CBP-1018 was eliminated immediately after injection and MMAE reached the maximum exposure at approximately 2 h after infusion. The maximum concentration of MMAE did not exceed 20.0 ng/mL, suggesting that the off-target toxicity of CBP-1018 injection was controllable.

Chromatographic Analysis of Aqueous Humor of Bupivacaine in Different Administration Approaches

Different administration approaches were investigated for the selection of bupivacaine administration type and a sensitive high-performance liquid chromatographic (HPLC) method has been developed. Developed method was validated and applied for the determination of bupivacaine in rabbit aqueous humor. The separation was achieved using a XTerra, C8 (250 × 8 mm i.d., particle size 5 μm) analytical column with a mobile phase consisted of acetonitrile and sodium dihydrogen phosphate (pH = 3.0, 20 mM; 30:70, v/v). Bupivacaine detection was performed by Diode Array detector (DAD) at 220 nm. The retention times for bupivacaine is 15.886 min. HPLC-DAD method was linear in the range of 75-4000 ng/mL. The limit of detection was 25 ng/mL and the limit of quantification of bupivacaine was found to be 75 ng/mL (relative standard deviation, RSD ≤ 15%, n = 6). In intra-day and inter-day precision and accuracy analysis, the RSD was found to be in the range of 0.96 and 7.98%, the bias values were 0.64 and 3.33%. Method was carried out for three different type of bupivacaine application because of the investigation of effective drug administration. Twenty aqueous humor samples were in the range of 0.642 and 5.124 μg/mL.

High-precision monitoring of and feedback control over drug concentrations in the brains of freely moving rats

Knowledge of drug concentrations in the brains of behaving subjects remains constrained on a number of dimensions, including poor temporal resolution and lack of real-time data. Here, however, we demonstrate the ability of electrochemical aptamer-based sensors to support seconds-resolved, real-time measurements of drug concentrations in the brains of freely moving rats. Specifically, using such sensors, we achieve <4 μM limits of detection and 10-s resolution in the measurement of procaine in the brains of freely moving rats, permitting the determination of the pharmacokinetics and concentration-behavior relations of the drug with high precision for individual subjects. In parallel, we have used closed-loop feedback-controlled drug delivery to hold intracranial procaine levels constant (±10%) for >1.5 hours. These results demonstrate the utility of such sensors in (i) the determination of the site-specific, seconds-resolved neuropharmacokinetics, (ii) enabling the study of individual subject neuropharmacokinetics and concentration-response relations, and (iii) performing high-precision control over intracranial drug levels.

Efficacy of prolonged intravenous lidocaine infusion for postoperative movement-evoked pain following hepatectomy: a double-blinded, randomised, placebo-controlled trial

BACKGROUND

The analgesic effect of intravenous lidocaine varies with the duration of lidocaine infusion and surgery type. We tested the hypothesis that prolonged lidocaine infusion alleviates postoperative pain in patients recovering from hepatectomy over the first 3 postoperative days.

METHODS

Patients undergoing elective hepatectomy were randomly assigned to receive prolonged i.v. lidocaine treatment or placebo. The primary outcome was incidence of moderate-to-severe movement-evoked pain at 24 h postoperatively. The secondary outcomes included incidence of moderate-to-severe pain during movement and at rest throughout the first 3 postoperative days, postoperative opioid consumption, and pulmonary complications. Plasma lidocaine concentration was also monitored.

RESULTS

We enrolled 260 subjects. Intravenous lidocaine lowered the incidence of moderate-to-severe movement-evoked pain at 24 h and 48 h postoperatively (47.7% vs 67.7%, P=0.001; 38.5% vs 58.5%, P=0.001) and reduced movement-evoked pain scores (3.7 [1.7] vs 4.2 [1.6]; mean difference 0.5 [95% confidence interval {CI}: 0.1-0.9]; P=0.018) and morphine equivalent consumption (47.2 [16.7] mg vs 52.6 [19.2] mg; mean difference 5.4 mg [95% CI: 1.0-9.8]; P=0.016) at 24 h postoperatively. Lidocaine also lowered the incidence of postoperative pulmonary complications (23.1% vs 38.5%; P=0.007). Median plasma lidocaine concentrations were 1.5, 1.9, and 1.1 μg ml^-1 (inter-quartile ranges: 1.1-2.1, 1.4-2.6, and 0.8-1.6, respectively) after bolus injection, at the end of the surgery, and 24 h postoperatively.

CONCLUSIONS

Prolonged intravenous lidocaine infusion reduced the incidence of moderate-to-severe movement-evoked pain for 48 h after hepatectomy. However, the reduction in pain scores and opioid consumption by lidocaine was below the minimal clinically important difference.

CLINICAL TRIAL REGISTRATION

NCT04295330.

Determination of Local Anesthetic Drugs in Human Plasma Using Magnetic Solid-Phase Extraction Coupled with High-Performance Liquid Chromatography

In this work, magnetic tetraethylenepentamine (TEPA)-modified carboxyl-carbon nanotubes were synthesized, characterized, and used as adsorbents to conduct magnetic solid-phase extraction (MSPE) for the preconcentration of seven local anesthetic drugs (procaine, lidocaine, mepivacaine, oxybuprocaine, bupivacaine, tetracaine, and cinchocaine) from human plasma. The separation and determination of analytes were performed on high-performance liquid chromatography with UV detection. Several factors affected the extraction efficiency, such as the amount of adsorbents used, extraction time, sample pH, and optimization of elution conditions. Under optimal conditions, satisfactory linear relationships were obtained in the range of 0.02-5.00 mg/L, with the limits of detection (LOD) ranging from 0.003 mg/L to 0.008 mg/L. The recoveries of analytes for spiked human plasma were in the range of 82.0-108%. Moreover, the precision with intra-day and inter-day RSD values were obtained in the range of 1.5-7.7% and 1.5-8.3%. The results indicated that this method could determine the concentration of seven local anesthetic drugs in human plasma with high precision and repeatability and provide support for the clinical monitoring of the concentration of local anesthetic drugs in human plasma.

A membrane-protected microsolid phase-extraction method based on molecular imprinting and its application to the determination of local anesthetics in cosmetics

As local anesthetics (LAs) that are illegally added into cosmetics are harmful to consumer health, it is necessary to establish an efficient method for detecting these substances. Herein, a molecularly imprinted polymer (bupivacaine) was prepared by bulk polymerization and packed into a hollow fiber for use as an extraction phase to fabricate a membrane-protected microsolid phase-extraction device. The optimal values of the influencing parameters for the microextraction process were as follows: a sample solution pH of 9.0, a loading and washing time of 2 h and an elution time of 32 min. A GC-MS method was established for determination of local anesthetics and coupled with the microextraction method to successfully detect local anesthetics in cosmetic samples. The calibration curve for the proposed method was linear in the range of 0.4∼50 mg/L and showed a good correlation coefficient (r² ). The LODs for local anesthetics were in the range of 0.01∼0.71 mg/L. The molecularly imprinted polymer exhibited good imprinting and selectivity, and the microsolid phase-extraction device was simple and inexpensive and fabrication was reproducible. The combination of molecular imprinting technology, membrane separation and microsolid phase-extraction methods used in this study can potentially be applied to pretreat local anesthetics in cosmetic samples. This article is protected by copyright. All rights reserved.

Comparison of ropivacaine plasma concentration after posterior Quadratus Lumborum Block in Cesarean Section with ropivacaine with epinephrine vs plane

BACKGROUND

The posterior Quadratus Lumborum Block (pQLB) has been used in postoperative pain management after Cesarean Section (CS). However, clinicians have no data about pQLB safety in pregnants, at increased risk of local anesthetic systemic toxicity (LAST). The purpose of the present study was to explore the efficacy and the safety of adding epinephrine to ropivacaine for bilateral pQLB vs. bilateral pQLB performed with ropivacaine alone in CS.

METHODS

in this prospective trial 52 pregnants, ASA 2 physiological status, were consecutively allocated to one of 2 groups, e-pQLB and pQLB; e-pQLB group received 0.375% ropivacaine+100 mcg epinephrine, 20 ml each side; pQLB received 0.375% ropivacaine alone, 20 ml each side. The primary and secondary outcomes were to evaluate if the adjunct of epinephrine to ropivacaine increases efficacy and safety of pQLB, respectively.

RESULTS

Authors found in e-pQLB group vs. p-QLB group: a total mean morphine consumption statistically lower during the first 24 postoperative hours (5.08±3.12, vs 9.11±4.67 SD mg, p=0.0002); NRS values statistically lower at 6 hours from block, both at rest (1,73±1,88 SD vs. 2,88±2,53, p=0.03) and with movement (3,03±1,98 SD vs. 4,23±2,87, p=0.04); a longer time between block and the first opioid request (5.92±2.48 vs 3.78±2.68 SD hrs, p< 0.003); venous ropivacaine concentrations significantly lower at any time of samples but at 120 minutes.

CONCLUSIONS

Adding epinephrine to ropivacaine increases efficacy and duration of pQLB. Moreover it increases block safety, reducing peak and mean venous ropivacaine concentration.

Studying the effect of vasopressors on therapeutic drug monitoring of two local anesthetics using hybrid micelle liquid chromatography as an analysis tool

A hybrid micelle based mobile phase was used to develop and validate a liquid chromatographic method for the separation and quantification of two local anesthetics namely; lidocaine hydrochloride (LID), and bupivacaine hydrochloride (BPV) in presence of the frequently co administered vasopressors phenyl ephrine (PHR) and ephedrine (EPH). Optimization of chromatographic separation conditions was performed applying experimental one factor at a time tool, and design of experiment, where the retention behavior of all analytes using both optimization protocols was in accordance. Chromatographic separation was carried on a C8 column operating at 40 °C at a flow rate of 1.5 mL/min. using a mobile phase consisting of 0.18 M sodium dodecyl sulphate, 10% acetonitrile, containing 0.3% triethyl amine and adjusted to pH 7 using 2 M ortho phosphoric acid, adopting UV detection at 230 nm. The proposed method was fully validated and applied to both in vitro and in vivo analysis of rat blood samples. The pharmacokinetics of both LID and BPV was followed when they were solitary injected or when co administered with either PHR or EPH. Moreover, the in vitro spiked experiment was also subjected to documented bio-analytical validation procedures.

Integration of Solid-Phase Extraction and Reversed-Phase Chromatography in Single Protein-Coated Columns for Direct Injection of Bupivacaine in Human Serum

A rapid, reliable and precise integrated solid-phase extraction (SPE) and reversed-phase liquid chromatography method was developed and validated to determine bupivacaine in human serum using single protein-coated analytical columns. The protein-coated columns were packed with four different sorbents: TSK-ODS, LiChrosorb RP-8, LiChrosorb RP-2 and μ-Bondapak CN-bonded silica. The method involved direct injection of serum sample onto the columns for trapping of the analyte, clean-up from weakly retained serum endogenous components, as well as the final separation. The protein-coated columns operated in two different chromatographic modes. Serum proteins were extracted and cleaned up by SPE, whereas the final separation of bupivacaine was based on reversed-phase chromatography. The protein-coated TSK-ODS column resulted in more accurate peak integration and more reproducible results. A linear relationship between the concentrations of drug and peak areas was confirmed in the range of 100-2000 ng/mL. Detection and quantification limits were 24.85 and 85.36 ng/mL, respectively. The average recovery for bupivacaine ranged from 96.48% to 98.81%. The present methodology was successfully applied, with a high degree of confidence, to analyze clinical samples obtained from patient receiving 0.5% bupivacaine therapy.

Formulation and optimisation of novel transfersomes for sustained release of local anaesthetic

Objective

To investigate the effect of formulation parameters on the preparation of transfersomes as sustained-release delivery systems for lidocaine and to develop and validate a new high-performance liquid chromatography (HPLC) method for analysis.

Method

Taguchi design of experiment (DOE) was used to optimise lidocaine-loaded transfersomes in terms of phospholipid, edge activator (EA) and phospholipid : EA ratio. Transfersomes were characterised for size, polydispersity index (PDI), charge and entrapment efficiency (%EE). A HPLC method for lidocaine quantification was optimised and validated using a mobile phase of 30%v/v PBS (0.01 m) : 70%v/v Acetonitrile at a flow rate of 1 ml/min, detected at 255 nm with retention time of 2.84 min. The release of lidocaine from selected samples was assessed in vitro.

Key findings

Transfersomes were 200 nm in size, with PDI ~ 0.3. HPLC method was valid for linearity (0.1–2 mg/ml, R2 0.9999), accuracy, intermediate precision and repeatability according to ICH guidelines. The %EE was between 44% and 56% and dependent on the formulation parameters. Taguchi DOE showed the effect of factors was in the rank order : lipid : EA ratio ˃ EA type ˃ lipid type. Optimised transfersomes sustained the release of lidocaine over 24 h.

Conclusion

Sustained-release, lidocaine-loaded transfersomes were successfully formulated and optimised using a DOE approach, and a new HPLC method for lidocaine analysis was developed and validated.

Rectal enema of bupivacaine in cancer patients with tenesmus pain - case series

Introduction: Rectal tenesmus pain in cancer patients most frequently appears in patients with colon cancer, and as a consequence of radiotherapy of the hypogastrium region. Treatment with opioids and adjuvant analgesics is often ineffective. Patients and methods: Here, we report on two female patients diagnosed with colon and ovary cancer, respectively, who had very severe tenesmus pain (numerical rating scale 8-10) despite using high doses of opioids, including methadone with corticosteroids, anticonvulsants, antidepressants and ketamine. Results: In both patients, bupivacaine was administered via a rectal enema. In the first patient, bupivacaine was administered at a dose of 100 mg 0.1% (100 mL), and subsequently 100 mg 0.2% (50 mL), leading to effective analgesia for 8 and 12 hrs, respectively. In the second patient, 100 mg 0.1% (100 mL) was initially administered, followed by 100 mg 0.2% (50 mL), leading to effective analgesia for 12 and 17 hrs, respectively, with only dull abdominal pain reported that was relieved by 100 mg IV ketoprofen and complete disappearance of tenesmus pain. Rectal bupivacaine administration did not cause neurologic adverse effects, heart function disturbances or decreased blood pressure. A volume of 50 mL was enough to cover a painful area in the colon. Initial bupivacaine concentrations in the blood serum did not exceed 50 ng/mL and eventually dropped to 20 ng/mL and below. Conclusions: Administration of 100 mg bupivacaine as a rectal enema is safe and provides effective analgesia, and this procedure may be conducted in hospital departments and out-patient clinics. Furthermore, this procedure in the case of pain recurrence, can be repeated, and by providing effective pain relief often allows time for the patient to be transferred to a specialized pain center.

Nanoscale Bupivacaine Formulations To Enhance the Duration and Safety of Intravenous Regional Anesthesia

Intravenous regional anesthesia (IVRA; Bier block) is commonly used to anesthetize an extremity for surgery. Limitations of the procedure include pain from the required tourniquet, the toxicity that can occur from systemic release of local anesthetics, and the lack of postoperative pain relief. We hypothesized that the nanoencapsulation of the local anesthetic would prolong local anesthesia and enhance safety. Here, we developed an ∼15 nm micellar bupivacaine formulation (M-Bup) and tested it in a rat tail vein IVRA model, in which active agents were restricted in the tail by a tourniquet for 15 min. After tourniquet removal, M-Bup provided local anesthesia for 4.5 h, which was two times longer than that from a larger dose of free bupivacaine. Approximately 100 nm liposomal bupivacaine (L-Bup) with the same drug dose as M-Bup did not cause anesthesia. Blood levels of bupivacaine after tourniquet removal were lower in animals receiving M-Bup than L-Bup or free bupivacaine, demonstrating enhanced safety. Tissue reaction to M-Bup was benign.

Electrochemical Oxidation of Amines Using a Nitroxyl Radical Catalyst and the Electroanalysis of Lidocaine

The nitroxyl radical of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) can electro-oxidize not only alcohols but also amines. However, TEMPO has low activity in a neutral aqueous solution due to the large steric hindrance around the nitroxyl radical, which is the active site. Therefore, nortropine N-oxyl (NNO) was synthesized to improve the catalytic ability of TEMPO and to investigate the electrolytic oxidation effect on amines from anodic current changes. Ethylamine, diethylamine, triethylamine, tetraethylamine, isopropylamine, and tert-butylamine were investigated. The results indicated that TEMPO produced no response current for any of the amines under physiological conditions; however, NNO did function as an electrolytic oxidation catalyst for diethylamine, triethylamine, and isopropylamine. The anodic current depended on amine concentration, which suggests that NNO can be used as an electrochemical sensor for amine compounds. In addition, electrochemical detection of lidocaine, a local anesthetic containing a tertiary amine structure, was demonstrated using NNO with a calibration curve of 0.1–10 mM.

A New Approach for the Determination of Benzocaine and Procaine in Pharmaceuticals by Single-Sweep Polarography

A new polarographic method for the determination of benzocaine and procaine based on the polarographic reduction of their chemically obtained oxidation products with potassium peroxymonosulfate is developed. Experimental conditions affecting quantitative yield of benzocaine and procaine oxidation products such as рH, oxidation time, reagents’ concentration, and temperature are explored. It is shown that the reduction current changes in a linear fashion (R=0.999) with increasing concentration of anesthetics over a concentration range of 1·10−6 - 5·10−5 mol L−1. The calculated limits of detection (LOD) for benzocaine and procaine are found to be 5.6·10−6 and 6·10−6 mol L−1, respectively. In the present study, quantitative polarographic determination of benzocaine in Farisil tablets and “Septolete Plus” lozenges and procaine in solution for injections is performed. The results of the analysis are in good agreement with the product specifications described in the quality certificates. The possibility of quantitative determination of benzocaine and procaine in pharmaceuticals is confirmed.

Enhanced HPLC-MS/MS method for the quantitative determination of the co-administered drugs ceftriaxone sodium and lidocaine hydrochloride in human plasma following an intramuscular injection and application to a pharmacokinetic study

A sensitive HPLC-MS/MS method was established for the quantification of ceftriaxone sodium (CFT) and lidocaine HCl (LDC) in human plasma utilizing cefixime (CFX) and tadalafil (TDA) as internal standards. The analytes were extracted from human plasma by protein precipitation using acetonitrile. Chromatographic separation was performed on Kinetex C₁₈ (50.0 × 4.6 mm, 5 μm particle size) column with methanol-0.01 M ammonium acetate pH 6.4 (70: 30, v/v) as mobile phase. Multiple reaction monitoring involving the transitions 555.10 → 396.20, 235.20 → 86.00, 454.20 → 284.80 and 390.20 → 268.20 was utilized to quantify CFT, LDC, CFX and TDA, respectively, using a triple quadrupole mass spectrometer which was operated in positive ion mode. The method revealed linearity in the concentration range of 3.0-300.0 μg/mL for CFT and 3.0-300.0 ng/mL for LDC. The validation of the method was achieved in accordance to the US Food and Drug Administration guidelines. A pharmacokinetic study was performed on healthy Egyptian volunteers after intramuscular injection of sterile ceftriaxone sodium (1 g CFT dissolved in 3.5 mL of 1% LDC) after approval from the ethics committee. The pharmacokinetic parameters were: C_max 141.15 ± 39.84 (μg/mL) and 55.02 ± 9.36 (ng/mL); t_max (h) 2.50 ± 0.50 and 1.5 ± 0.50; t_½ (h) 7.30 ± 2.98 and 4.23 ± 1.96; and K_el (h^-1 ) 0.10 ± 0.04 and 0.20 ± 0.13 for CFT and LDC, respectively.

A High-Performance Liquid Chromatography Assay Method for the Determination of Lidocaine in Human Serum

Here we report on the development of a selective and sensitive high-performance liquid chromatographic method for the determination of lidocaine in human serum. The extraction of lidocaine and procainamide (internal standard) from serum (0.25 mL) was achieved using diethyl ether under alkaline conditions. After liquid–liquid extraction, the separation of analytes was accomplished using reverse phase extraction. The mobile phase, a combination of acetonitrile and monobasic potassium phosphate, was pumped isocratically through a C18 analytical column. The ultraviolet (UV) wavelength was at 277 nm for the internal standard, and subsequently changed to 210 for lidocaine. The assay exhibited excellent linearity (r² > 0.999) in peak response over the concentration ranges of 50–5000 ng/mL lidocaine HCl in human serum. The mean absolute recoveries for 50 and 1000 ng/mL lidocaine HCl in serum using the present extraction procedure were 93.9 and 80.42%, respectively. The intra- and inter-day coefficients of variation in the serum were <15% at the lowest, and <12% at other concentrations, and the percent error values were less than 9%. The method displayed a high caliber of sensitivity and selectivity for monitoring therapeutic concentrations of lidocaine in human serum.

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.

Ultrasound-Guided Quadratus Lumborum Block: An Updated Review of Anatomy and Techniques

Purpose of Review. Since the original publication on the quadratus lumborum (QL) block, the technique has evolved significantly during the last decade. This review highlights recent advances in various approaches for administering the QL block and proposes directions for future research. Recent Findings. The QL block findings continue to become clearer. We now understand that the QL block has several approach methods (anterior, lateral, posterior, and intramuscular) and the spread of local anesthetic varies with each approach. In particular, dye injected using the anterior QL block approach spread to the L1, L2, and L3 nerve roots and within psoas major and QL muscles. Summary. The QL block is an effective analgesic tool for abdominal surgery. However, the best approach is yet to be determined. Therefore, the anesthetic spread of the several QL blocks must be made clear.

Self-initiated and concentration-dependent degradation of tetracaine in neat standard solutions: A trouble-shooting story

This paper presents the trouble-shooting for a very unusual stability case. Tetracaine was found unstable in neat solutions only at high concentrations, but not at low concentrations. Moreover, its stable-isotope labeled internal standard did not show similar behavior. A series of trouble-shooting experiments were conducted to uncover the root cause. Some generally applicable precautions/insights can be drawn from this investigation to avoid potential stability issues during bioanalytical method development and validation.

Efficacy and Safety of a Lidocaine and Ropivacaine Mixture for Scalp Nerve Block and Local Infiltration Anesthesia in Patients Undergoing Awake Craniotomy

BACKGROUND

Mixtures of various local anesthetics, such as lidocaine and ropivacaine, have been widely used. However, their efficacy and safety for scalp nerve blocks and local infiltration during awake craniotomy have not been fully elucidated.

METHODS

We prospectively investigated 53 patients who underwent awake craniotomy. Scalp block was performed for the blockade of the supraorbital, supratrochlear, zygomaticotemporal, auriculotemporal, greater occipital, and lesser occipital nerves with a mixture containing equal volumes of 2% lidocaine and 0.75% ropivacaine, including 5 μg/mL of epinephrine. Infiltration anesthesia was applied at the site of skin incision using the same mixture. The study outcomes included changes in heart rate and blood pressure after head pinning and skin incision, and incidence of severe pain on emergence from anesthesia. Total doses and plasma concentrations of lidocaine and ropivacaine were measured at different time points after performing the block.

RESULTS

The heart rate and blood pressure after head pinning were marginally, but significantly, increased when compared with baseline values. There were no significant differences in heart rate and blood pressure before and after the skin incision. Nineteen percent of the patients (10/53) complained of incisional pain at emergence from anesthesia. The highest observed blood concentrations of lidocaine and ropivacaine were 1.9±0.9 and 1.1±0.4 μg/mL, respectively. No acute anesthetic toxicity symptom was observed.

CONCLUSIONS

Scalp block with a mixture of lidocaine and ropivacaine seems to provide effective and safe anesthetic management in patients undergoing awake craniotomy.

Retrolaminar block: analgesic efficacy and safety evaluation

PURPOSE

Retrolaminar block (RLB) is a thoracic truncal block that can produce analgesia for the thoracic and abdominal wall. However, the characteristics of RLB are not well known. The aim of this study was to determine analgesic efficacy by measuring postoperative consume of patient-controlled analgesia (PCA), additional nonsteroidal antiinflammatory drug (NSAID) rescue, and opioid rescue. Our secondary analysis included assessment of the chronological change in arterial levobupivacaine concentrations after the block.

METHODS

This prospective, randomized, double-blinded study included 30 patients scheduled for modified radical mastectomy under general anesthesia. The patients were randomized to receive either a landmark-guided RLB or paravertebral block (PVB) catheter placement on T4. Continuous infusion with 4 ml/h of 0.25 % levobupivacaine was started for 72 h, after initial injection of 20 ml 0.375 % levobupivacaine before surgery. Postoperative pain was compared using the amount of block PCA (3 ml 0.25 % levobupivacaine with 30-min lockout), NSAID, and opioid rescue. Arterial blood was sampled for 120 min after the initial injection.

RESULTS

The frequency of postoperative block PCA use was significantly high after RLB in 24 h [p = 0.01; 6 (3-12) vs. 2.5 (0.3-3) times, respectively]. There was no PCA use after 24 h in either group. There was no postoperative opioid rescue use throughout the study. After RLB and PVB, there was no significant difference in T _max (p = 0.14; 15 ± 8 vs. 15 ± 8 min, respectively) and C _max (p = 0.2; 0.9 ± 0.2 vs. 0.9 ± 0.3 µg/ml, respectively), and all the concentrations were below the threshold of local anesthetic systemic toxicity.

CONCLUSION

Continuous RLB was not inferior to PVB except for the first 24 h, and was satisfactory after mastectomy. RLB showed safe, low peak arterial levobupivacaine concentrations.

Development of a HPLC-MS/MS method for the simultaneous determination of nifedipine and lidocaine in human plasma

The method for simultaneous determination of nifedipine (NIF) and lidocaine (LID) in human plasma by one-step sample preparation has been developed for the first time. Due to the photosensitivity of nifedipine and its low plasma concentrations a precise and reliable method was required. The method involved liquid-liquid extraction (methyl tert-butyl ether, MTBE), and 10μL of the resulting sample was analyzed by HPLC-MS/MS. Chromatographic separation was achieved on an YMC-Triart C18 HPLC column (100×2.0mm; S-5μm 12nm). The mobile phase was methanol:water, 60:40 (v/v) and contained 0.15% acetic acid. The linearity of the method was established in the concentration ranges of 0.5-50ng/mL for NIF and 1.0-500ng/mL for LID. Photodestruction of NIF under ambient light was evaluated. The validated method was successfully applied to analyze human plasma samples after rectal application of the drug (1g) containing 2.0% LID and 0.3% NIF.

The efficacy of simultaneous bilateral axillary brachial plexus block under the guidance of neurostimulator or ultrasound: a prospective study

PURPOSE

This study was designed to investigate the risk of local anesthetic toxicity and efficacy of simultaneous bilateral axillary brachial plexus block performed under the guidance of ultrasound or a neurostimulator.

METHODS

One hundred and twenty patients who were anesthetized with bilateral axillary plexus block simultaneously between February 2012 and March 2014 were enrolled in the study. The patients were anesthetized under the guidance of a neurostimulator (group N, n = 60) or ultrasound (group U, n = 60). The block performance time, procedure-related pain, adverse events, total and free plasma concentrations of ropivacaine, and other data were recorded. The comparison was analyzed statistically.

RESULTS

The block performance time, and onset of the sensory and motor block, of group N was longer than that of group U (p < 0.001). The procedure-related pain of group N was more serious than that of group U (p < 0.05). The patient satisfaction rate of group U was higher than that of group N (p < 0.05). The total plasma concentrations of ropivacaine in group N were comparable to those of group U, except for the value at 50 min after injection (p < 0.05). The free plasma concentrations of ropivacaine of group N at 5 min were significantly higher than that of group U (p < 0.001). No apparent serious adverse events were observed perioperatively in both groups.

CONCLUSIONS

Simultaneous bilateral axillary brachial plexus block guided by neurostimulator or ultrasound in bilateral distal upper extremity surgery seems to have a low risk of local anesthetic toxicity and to be effective. The ultrasound-guided block is superior in terms of providing the same degree of anesthesia with shorter duration, less pain, and faster onset of sensory and motor blockades, which is important in clinical practice.

Quadratus Lumborum Block: Analgesic Effects and Chronological Ropivacaine Concentrations After Laparoscopic Surgery

BACKGROUND AND OBJECTIVES

The quadratus lumborum block (QLB) is an abdominal truncal block, similar to transversus abdominis plane block (TAPB). However, the characteristics of QLB with regard to its duration and safety are not well known. The primary aim of this study was to determine the block duration and the cutaneous sensory block area. Our secondary analysis included assessment of the chronological change in arterial local anesthetic concentrations after QLB.

METHODS

This study included 11 patients scheduled for laparoscopic ovarian surgery under general anesthesia. The patients received bilateral single-injection QLBs (20 mL of 0.375% ropivacaine per side). Arterial blood was sampled at 10, 20, 30, 45, 60, 90, and 120 minutes after ropivacaine administration. The results were retrospectively compared with the results of our previous study on lateral TAPB.

RESULTS

The median duration of analgesia after QLB exceeded 24 hours and was significantly longer than the duration of lateral TAPB (P = 0.003). Quadratus lumborum block affected the T7-T12 dermatomes, whereas TAPB affected T10-T12. Arterial ropivacaine levels after block peaked at comparable time in the QLB and lateral TAPB groups (Tmax: 35 [SD, 13] vs 35 [SD, 11] minutes; P = 0.93). Peak ropivacaine concentrations were significantly lower in QLB than in lateral TAPB (Cmax: 1.0 [SD, 0.5] vs 1.8 [SD, 0.4] μg/mL; P = 0.0003).

CONCLUSIONS

Quadratus lumborum block resulted in a widespread and long-lasting analgesic effect after laparoscopic ovarian surgery and resulted in lower peak arterial ropivacaine concentrations as compared with those of lateral TAPB after 150 mg ropivacaine injection.

Chromatographic Determination of Aminoacridine Hydrochloride, Lidocaine Hydrochloride and Lidocaine Toxic Impurity in Oral Gel

Two sensitive and selective analytical methods were developed for simultaneous determination of aminoacridine hydrochloride and lidocaine hydrochloride in bulk powder and pharmaceutical formulation. Method A was based on HPLC separation of the cited drugs with determination of the toxic lidocaine-related impurity 2,6-dimethylaniline. The separation was achieved using reversed-phase column C18, 250 × 4.6 mm, 5 µm particle size and mobile phase consisting of 0.05 M disodium hydrogen phosphate dihydrate (pH 6.0 ± 0.2 adjusted with phosphoric acid) and acetonitrile (55 : 45, v/v). Quantitation was achieved with UV detection at 240 nm. Linear calibration curve was in the range of 1.00-10.00, 13.20-132.00 and 1.32-13.20 µg mL(-1) for aminoacridine hydrochloride, lidocaine hydrochloride and 2,6-dimethylaniline, respectively. Method B was based on TLC separation of the cited drugs followed by densitometric measurement at 365 nm on the fluorescent mode for aminoacridine hydrochloride and 220 nm on the absorption mode for lidocaine hydrochloride. The separation was carried out using ethyl acetate-methanol-acetic acid (65 : 30 : 5 by volume) as a developing system. The calibration curve was in the range of 25.00-250.00 ng spot(-1) and 0.99-9.90 µg spot(-1) for aminoacridine hydrochloride and lidocaine hydrochloride, respectively. The results obtained were statistically analyzed and compared with those obtained by applying the manufacturer's method.

Validated RP-HPLC and TLC-Densitometric Methods for Analysis of Ternary Mixture of Cetylpyridinium Chloride, Chlorocresol and Lidocaine in Oral Antiseptic Formulation

This work was concerned with development, optimization, application and validation of reversed phase high performance liquid chromatography (RP-HPLC) and thin layer chromatography (TLC)-densitometric methods for analysis of cetylpyridinium chloride, chlorocresol and lidocaine in Canyon(®) gel. The first developed RP-HPLC method depended on chromatographic separation on a ZORBAX Eclipse Plus C8 column, with elution with a mobile phase consisting of 0.05% phosphoric acid solution : acetonitrile : methanol (15 : 24 : 61, by volume), pumping the mobile phase at a flow rate of 1.00 mL min(-1), with ultraviolet detection at 220 nm. While in the subsequently developed method, the TLC-densitometric method, complete separation of the studied mixture was achieved using methanol : acetone : acetic acid (7 : 3 : 0.2, by volume) as a mobile phase, aluminum plates precoated with silica gel 60 F254 as a stationary phase and 215 nm as the scanning wavelength. Factors affecting the developed methods were studied and optimized; moreover, methods had been validated as per the International Conference of Harmonization guideline and the results indicated that the suggested methods were reproducible, reliable and applicable for rapid routine analysis. Statistical comparison of the two developed methods with the reported HPLC ones using F- and Student's t tests showed no significant difference.

Visceral mesh modified with cyclodextrin for the local sustained delivery of ropivacaine

The aim of the study was to develop a polyester visceral implant modified with a cyclodextrin polymer for the local and prolonged delivery of ropivacaine to reduce post operatory pain. Therefore, we applied a coating of an inguinal mesh with a crosslinked polymer of hydroxypropyl-β-cyclodextrin (HPβCD) whose specific host-guest complex forming properties were expected to improve the adsorption capacity of the implant toward anesthetic, and then to release it within a sustained period. The modification reaction of the textile with cyclodextrin was explored through the study of the influence of the pad/dry/cure process parameters and the resulting implant (PET-CD) was characterized by solid state NMR and SEM. Besides, the inclusion complex between ropivacaine and CD was studied by NMR and capillary electrophoresis in PBS medium. Finally, ropivacaine sorption test showed that a maximum of 30 mg/g of ropivacaine could be adsorbed on the functionalized samples. In dynamic batch tests in PBS at pH 7.4, the release could be observed up to 6h. The cytocompatibility of the PET-CD loaded with ropivacaine was also studied and reached 65% cell vitality after 6 days.

Lumbar paravertebral blockade as intractable pain management method in palliative care

Optimal symptoms control in advanced cancer disease, with refractory to conventional pain treatment, needs an interventional procedure. This paper presents coadministration of local anesthetic (LA) via paravertebral blockade (PVB) as the alternative to an unsuccessful subcutaneous fentanyl pain control in a 71-year old cancer patient with pathological fracture of femoral neck, bone metastases, and contraindications to morphine. Bupivacaine in continuous infusion (0.25%, 5 mL · hour⁻¹) or in boluses (10 mL of 0.125%–0.5% solution), used for lumbar PVB, resulted in pain relief, decreased demand for opioids, and led to better social interactions. The factors contributing to an increased risk of systemic toxicity from LA in the patient were: renal impairment; heart failure; hypoalbuminemia; hypocalcemia; and a complex therapy with possible drug-drug interactions. These factors were taken into consideration during treatment. Bupivacaine’s side effects were absent. Coadministered drugs could mask LA’s toxicity. Elevated plasma α1-acid glycoprotein levels were a protective factor. To evaluate the benefit-risk ratio of the PVB treatment in boluses and in constant infusion, bupivacaine serum levels were determined and the drug plasma half-lives were calculated. Bupivacaine’s elimination was slower when administered in constant infusion than in boluses (t_½ = 7.80 hours versus 2.64 hours). Total drug serum concentrations remained within the safe ranges during the whole treatment course (22.9–927.4 ng mL⁻¹). In the case presented, lumbar PVB with bupivacaine in boluses (≤ 137.5 mg · 24 hours⁻¹) was an easy to perform, safe, effective method for pain control. Bupivacaine in continuous infusion (≤150 mg · 12 hours⁻¹) had an acceptable risk-benefits ratio, but was ineffective.

Determination of tissue distribution of potent antitumor agent ureidomustin (BO-1055) by HPLC and its pharmacokinetic application in rats

Ureidomustin hydrochloride (BO-1055) was designed as a water-soluble nitrogen-mustard, which exhibited potent anticancer activity and was selected as a candidate for preclinical studies. However, up to date, there is rarely an easy and economic method to quantize ureidomustin in the biological samples. The aim of this study is to develop a simple yet valid quantization method to tackle this challenge. Here we present a combined high-performance liquid chromatography with photodiode array (HPLC-PDA) method in quantizing the ureidomustin in the plasma and various organs of Sprague-Dawley rats. The method was validated in terms of precision, accuracy, and extraction recovery. Furthermore, the established method was applied to study pharmacokinetics of ureidomustin in the rat's plasma and verified via a liquid chromatography tandem mass spectrometry (LC-MS/MS) method. Calibration curves of the plasma and organ samples were falling at the range between 0.5-50μg/mL and 0.1-50μg/mL (r(2)≥0.999 and CV≤±15%), respectively. The limits of detection (LOD) were 0.1μg/mL for plasma samples and 0.05μg/mL for organ samples, while the detection limits of quantification (LOQ) were 0.5μg/mL for plasma samples and 0.1μg/mL for organ samples. The average recovery of ureidomustin was about 83%. These results demonstrated a linear pharmacokinetic pattern at dosages of 10 and 30mg/kg. The pharmacokinetic data revealed that ureidomustin was best fitted to a two-compartment model with a rapid distribution phase and a slow elimination phase. Besides, after a short intravenous administration time at the dose of 10mg/kg, ureidomustin was found to be quickly distributed to all organs in rats, accumulated mainly in the kidney, and only a limited amount was detected in the brain.