Rapid and specific precolumn extraction high-performance liquid chromatographic assay for bupivacaine in human serum

Green Automated Solid Phase Extraction to Measure Levofloxacin in Human Serum via Liquid Chromatography with Fluorescence Detection for Pharmacokinetic Study

A simple, selective, rapid, sensitive and less costly green automated solid phase extraction bio-analytical high-performance liquid chromatographic-based technique with fluorescence detection (Aut-SPE-BA-HPLC-FL) for the quantification of levofloxacin in human serum samples has been developed and validated. The serum samples were loaded into the chromatographic system without prior treatment and then injected into short (20 mm × 4.6 mm, 20 µm) protein-coated (PC) µBondapak CN (µBCN) silica pre-column (PC-µBCN-pre-column). Levofloxacin was retained and pre-concentrated on the head of the PC-µBCN-pre-column, while proteins and other polar components were eliminated using phosphate buffer saline (PBS), pH 7.4, as the first mobile phase in the extraction step. Levofloxacin is then transferred to the analytical column; ZORBAX Eclipse XDB-C18 (150 mm × 46 mm, 5 µm), through the aid of a column-switching valve technique, on-throughs the elution mode using the second mobile phase containing a methanol and phosphate buffer (0.05 M, pH 5) in a ratio of 70:30 (v/v). Levofloxacin signals were detected using a fluorescence detector operated at excitation/emission wavelengths of 295/500 nm. The proposed Aut-SPE-BA-HPLC-FL methodology showed linearity over a levofloxacin concentration range of 10–10,000 ng/mL (r2 = 0.9992), with good recoveries ranging from 87.12 to 97.55%. Because of the validation qualities in terms of linearity, recovery, precision, accuracy, selectivity and robustness, the Aut-SPE-BA-HPLC-FL method has been used in some clinical trials for therapeutic drug monitoring and the pharmacokinetic study of levofloxacin in human serum.

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.

S-wave in lead III is helpful for the early detection of bupivacaine-induced cardiac depression in dogs

PURPOSE

Unintentional intravascular bupivacaine injection is known to be associated with treatment-resistant cardiovascular collapse. Therefore, it is important for safe anesthetic management to establish an early sign of bupivacaine-induced cardiac depression with available monitoring. We hypothesized that bupivacaine induced-cardiac depression in dogs could be detected early by analyzing the electrocardiogram (ECG). We performed this study to investigate changes of ECG and ultimately find a variable reflecting cardiac output (CO) changes in dogs with bupivacaine-induced cardiac depression.

METHODS

Bupivacaine was infused into pentobarbital-anesthetized dogs (n = 9) at a rate of 0.5 mg x kg(-1) x min(-1) for 30 min. R-wave, S-wave and T-wave amplitudes in leads I, II and III were measured every five minutes after the start of bupivacaine infusion, and electrical axes of the heart were calculated at each time. The PR interval, QRS complex duration and corrected QT interval were also measured. CO, mean arterial blood pressure and heart rate were recorded at five-minute intervals. The relationships between CO and ECG wave parameters and of CO vs the hemodynamic variables were compared by correlation coefficients and regression analysis.

RESULTS

The electrical mean axis of the heart was deviated to the left by the bupivacaine infusion. S-wave in lead III increased approximately twice within the first five minutes and showed the closest correlation with CO (r = 0.751, P < 0.001) during 30 min bupivacaine infusion.

CONCLUSION

Close monitoring of an ECG, and especially the S-wave amplitude in lead III can be helpful for the early detection of bupivacaine-induced cardiac depression in dogs.

Simultaneous determination of bupivacaine, mepivacain, prilocaine and ropivacain in human serum by liquid chromatography–tandem mass spectrometry

A liquid chromatography-tandem mass spectrometric (LC-MS-MS) method with a rapid and simple sample preparation was developed and validated for the simultaneous determination of the local anesthetics bupivacaine, mepivacaine, prilocaine and ropivacaine in human serum. An external calibration was used. The mass spectrometer was operated in the multiple reaction monitoring mode. A good quadratic response over the range of 1.0-200.0 ng/ml was demonstrated. The accuracy for bupivacaine ranged from 93.2 to 105.7%, for mepivacaine from 96.2 to 104.3%, for prilocaine from 94.6 to 105.7% and for ropivacaine from 94.3 to 104.0%, respectively. The limit of quantification was 1.0 ng/ml for all substances. This method is suitable for pharmacokinetic studies.

Insulin reverses bupivacaine-induced cardiac depression in dogs

We tested the hypothesis that an insulin infusion would effectively treat bupivacaine-induced cardiac depression in dogs. In 24 mongrel dogs anesthetized with pentobarbital (5 mgkg(-1)h(-1), IV), 0.5% bupivacaine was administrated at a rate of 0.5 mgkg(-1)min(-1) until the mixed venous oxygen saturation decreased to 60% or less. The bupivacaine infusion induced a decrease in mean arterial pressure, cardiac output, and heart rate. The dogs were randomly assigned to one of four groups after the end of bupivacaine infusion. The Control (C, n = 6) and Glucose (G, n = 6) groups received an IV infusion of normal saline (2 mL/kg) and glucose (2 mL/kg of 50% dextrose in water) for 15 min, respectively. The Insulin-Glucose (IG, n = 6) group received an IV bolus of regular insulin (1 U/kg), plus a glucose infusion (2 mL/kg of 50% dextrose in water) for 15 min. The Insulin-Glucose-Potassium (IGK, n = 6) group received the same dose of insulin and glucose as the IG group, plus potassium (1-3 mEqkg(-1)h(-1)). Mean arterial pressure, cardiac output, heart rate, and mixed venous oxygen saturation recovered toward baseline level more rapidly in the IG and IGK groups than in the C group (within 5 min versus more than 20 min). These results suggest that the infusion of insulin and glucose might reverse bupivacaine-induced cardiac depression in dogs.

IMPLICATIONS

We found that insulin and glucose rapidly reversed hemodynamic abnormality in dogs with bupivacaine-induced cardiac depression. This study implies a possible clinical application of insulin treatment for bupivacaine-induced cardiac depression.

Chromatographic assay and pharmacokinetic studies of propofol in human serum

A high-performance liquid chromatographic system with automated precolumn extraction was developed for the determination of propofol in human serum. Propofol of directly injected serum sample was enriched on a protein-coated mu Bondapak phenyl precolumn while serum constituents such as proteins and salts were eluted to waste. Thereafter, using an on-line column-switching system, the drug was quantitatively transferred and separated on a second analytical column followed by spectrophotometric determination at 270 nm. Good precision, accuracy and linearity were obtained over a range of 30-3000 ng/mL propofol in human serum. The developed method proved to be fast, simple, reproducible, reliable and therefore convenient for propofol monitoring from serum. The recovery of propofol in serum samples from the lowest to the highest concentration ranged from 96.84 to 100.16% (n = 5). The assay was applied to study the pharmacokinetic of the drug in six women undergoing elective caesarean section under general anaesthesia induced with a single intravenous bolus dose of propofol (2.5 mg/kg).

Rapid determination of methotrexate in plasma by high-performance liquid chromatography with on-line solid-phase extraction and automated precolumn derivatization

A high-performance liquid chromatographic system, combining solid-phase extraction and automated precolumn derivatization is described for the routine determination of methotrexate in human plasma. The sample extraction and elution onto the analytical column were performed automatically and concomitantly using the column-switching technique and a protein-coated precolumn. Cerium (IV) trihydroxyhydroperoxide (CTH) was introduced as a packed oxidant before the analytical column for the conversion of methotrexate into highly fluorescent products. The oxidative-cleavage of methotrexate occurs during the flow of 0.04 M phosphate buffer (pH 3.5) containing plasma sample through CTH column with a flow rate of 0.5 mL/min at 40 degrees C. The fluorescent products were transferred to the protein-coated precolumn, which was then flushed with the same buffer for clean-up and enrichment from plasma sample. The trapped substances were desorbed from the precolumn and eluted onto the ODS/TM analytical column by isocratical elution with a mobile phase containing 0.05 M phosphate buffer, pH 6.6 and acetonitrile (90-10, v/v) for subsequent separation. The fluorescent products were detected fluorimetrically at excitation and emission wavelengths of 367 and 463 nm, respectively. The complete analysis was achieved within 15 min per sample. The calibration graph was linear in the range of 50-500 ng/mL of methotrexate and there was no interference from endogenous components.

Development of highly sensitive and specific HPLC assay for plasma morphine using direct injection technique and post-column derivatization

An extremely simple, rapid and reproducible analytical method was developed for the determination of morphine in human plasma using a high performance liquid chromatography utilizing a column-switching technique and protein-coated precolumn. Morphine from plasma (500 microL) was preconcentrated on the protein-coated pre-column without sample pre-treatment. This column acted at the same time as a clean up device. The drug was transferred on-line to the analytical column followed by post-chromatographic derivatization and fluorimetric detection. Post-column derivatization was based on the oxidative dimerization of morphine to fluorescent pseudomorphine by potassium hexacyanoferrate (III). The average morphine recoveries over a concentration range of 10 to 100 ng/mL ranged from 94.84 to 100.70%, and relative standard deviations ranged from 1.36 to 2.13%.