Enantiospecific analysis of ibuprofen by high performance liquid chromatography: Determination of free and total drug enantiomer concentrations in serum and urine

Chiral pharmacokinetics of ibuprofen enantiomers in Chinese preterm neonates with patent ductus arteriosus using a validated UHPLC-MS/MS method

Persistent patent ductus arteriosus (PDA) is generally observed in preterm neonates. Oral ibuprofen is the standard treatment for closing PDA in China. To investigate the chiral pharmacokinetics of ibuprofen enantiomers in Chinese premature infants with PDA, a simple, fast, and sensitive analytical enantioselective technology was developed with ultra-performance liquid chromatography (UPLC) - tandem mass spectrometry (MS/MS). Chromatographic separation of (R)-ibuprofen and (S)-ibuprofen was accomplished on a Lux® 3 µm Cellulose-3 (150 mm × 2.0 mm, 3 μm) at a flow rate of 0.2 mL/min within 6 min. UPLC separation was achieved by isocratic elution with a mobile phase consisting of formic acid:water (75:1000000, v/v) and acetonitrile:methanol (1:1, v/v). Only 50 µL of plasma samples were pre-treated with acetonitrile precipitation. Ibuprofen-d3 was used as an internal standard. The standard curves of both enantiomers were linear over a concentration range of 0.0500 μg/mL to 50.00 μg/mL. The method has been validated for selectivity, carryover effect, lower limit of quantification, precision, accuracy, matrix effect, extraction recovery, dilution integrity, and stability based on the existing guidelines of the National Medical Products Administration, the United States Food and Drug Administration, and the European Medicines Agency. This method has been successfully applied to investigate the pharmacokinetics of ibuprofen enantiomers in 9 preterm infants with PDA. Our results showed that a high chiral inversion ratio of (R)- to (S)-ibuprofen exists in Chinese preterm neonates. Further studies should be conducted to monitor drug concentration following oral administration of ibuprofen and to consider the effect of individual variations and ethnic differences in metabolizing enantiomers of ibuprofen in premature neonates with PDA.

A Validated Chiral LC–MS/MS Method for the Enantioselective Determination of (S)-(+)- and (R)-(-)-Ibuprofen in Dog Plasma: Its Application to a Pharmacokinetic Study

The purpose of this study was to develop a method for simultaneously separating ibuprofen enantiomers using electrospray ionization (ESI) liquid chromatography with tandem mass spectrometry (LC–MS/MS). LC–MS/MS was operated with negative ionization and multiple reaction monitoring modes; transitions were monitored at m/z of 205.1 > 160.9 for ibuprofen enantiomers, 208.1 > 163.9 for (S)-(+)-ibuprofen-d3 [internal standard 1 (IS1)], and 253.1 > 208.9 for (S)-(+)-ketoprofen (IS2), respectively. In a one-step liquid–liquid extraction, 10 μL plasma was extracted with ethyl acetate:methyl tertiary-butyl ether of 7:3. Enantiomer chromatographic separation was carried out with an isocratic mobile phase consisting of 0.008% formic acid in water–methanol (v/v) at a flow rate of 0.4 mL/min on a CHIRALCEL® OJ-3R column (150 × 4.6 mm, 3 µm). This method was fully validated for each enantiomer and results were in compliance with the regulatory guidelines of the U.S. Food and Drug Administration and the Korea Ministry of Food and Drug Safety. The validated assay was executed for nonclinical pharmacokinetic studies after oral and intravenous administration of racemic ibuprofen and dexibuprofen in beagle dogs.

Determination of ibuprofen enantiomers in human plasma by HPLC–MS/MS: validation and application in neonates

Aim: An adaptive method to determine ibuprofen enantiomers with limited volume of plasma required is necessary for investigating PK of ibuprofen in neonates. Results: Enantiomer separation was achieved on a Lux cellulose 3 column with mobile phase consisting of methanol water (85:15, v/v) and formic acid (0.0075%) at isocratic rate of 0.2 ml/min. Calibration curve is linear for each enantiomer at the range of 0.1–60 μg/ml. Validation was conducted and results met requirements regarding to intra- and inter-run precision, accuracy and recovery. No matrix effect or interference was observed from neonatal plasma or comedications. Only 20 μl of plasma was requested in this study. Conclusion: This assay was specific and reliable to quantify ibuprofen enantiomers in neonate plasma.

Determination of (S)-(+)- and (R)-(-)-ibuprofen enantiomers in human plasma after chiral precolumn derivatization by reversed-phase LC–ESI-MS/MS

Background: A selective, sensitive and high-throughput LC–ESI-MS/MS method has been developed and validated for the chromatographic separation and quantitation of (S)-(+)-ibuprofen and (R)-(-)-ibuprofen after derivatization with (S)-(-)-1-(1-napthyl)ethylamine using 1-hydroxybenzotriazole as the activator of the carboxylic acid group and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide as the coupling reagent in human plasma. Results: Both the analytes were chromatographically separated with a resolution factor of 1.27 on a Kinetex PFP (50 × 4.6 mm, 2.6 µm) analytical column. The method was validated over the concentration range of 0.10–32.0 µg/ml for both the enantiomers. The magnitude of matrix effect was assessed by post-column analyte infusion and also by precision (%CV) values for the calculated slopes of calibration curves. The mean extraction recovery was >91% for both the enantiomers. Conclusion: The method was successfully applied to a bioequivalence study in 34 healthy human subjects. The assay reproducibility was confirmed by reanalysis of 130 subject samples.

Quantitative analysis of ibuprofen in pharmaceuticals and human control serum using kinetic spectrophotometry

The aim of this work was to develop a new kinetic spectrophotometric method for the determination of ibuprofen in pharmaceutical formulations. Ibuprofen was determined in an acidic ethanolic medium by monitoring the rate of appearance of 1-nitroso-2-naphthol, resulting from the displacement by ibuprofen of Co(III) from the tris(1-nitroso-2-naptholato)cobalt(III) complex. The optimum operating conditions regarding reagent concentrations and temperature were established. The tangent method was adopted for constructing the calibration curve, which was found to be linear over the concentration range 0.21-1.44 and 1.44-2.06 ?g ml-1. The optimized conditions yielded a theoretical detection limit of 0.03 ?g ml-1 based on the 3.3 S0 criterion. The interference effects of the usual excipients of powdery drugs, foreign ions and amino acids on the reaction rate were studied in order to assess the selectivity of the method. The developed procedure was successfully applied for the rapid determination of ibuprofen in commercial pharmaceutical formulations and human control serum. The unique features of this procedure are that the determination can be performed at room temperature and the analysis time is short. The newly developed method is simple, inexpensive and efficient for use in the analysis of a large number of samples.

Pharmacokinetic applications of capillary electrophoresis: A review on recent progress

This article covers recent publications from 2003 to 2005 on the subject of pharmacokinetic applications of CE. Many analytical methods were validated and more importantly, they were shown to have sufficient sensitivities to access pharmacokinetic data on different models. Because of unique advantages, such as simplified sample preparation methods, small sample amount required, high separation power, and speedy analysis, CE-based assays were found to gain popularity not only as a second method but also as a major method for many pharmacokinetic studies.

Preparation and stereochemical integrity of certain thioesters of 2-arylpropionic acids and related compounds

2-Arylpropionate thioesters 5, 6a/6b and 7a/7b, 2-aryloxypropionate thioesters 8a/8b and 2-alkoxy-2-arylacetate thioesters 9a/9b were prepared from thiol 4 and the corresponding carboxylic acids. Thioesters 6a/6b, 7a/7b, 8a/8b and 9a/9b were monitored for evidence of inter-conversion between epimers in acetonitrile solvent at 40 degrees C, by optical activity in the cases of 6a/6b and 7a/7b, and by 1H NMR spectroscopy in the cases of 8a/8b and 9a/9b. Only in the case of thioesters 9a/9b was significant inter-conversion between epimers observed.

Determination of ibuprofen and tetrazepam in human urine by micellar electrokinetic capillary chromatography

A new micellar electrokinetic capillary chromatography method (MEKC) is proposed for the determination of ibuprofen and tetrazepam in human urine samples over a concentration range of therapeutic interest. A fused silica capillary (60 cm x 75 microm) is used. Ibuprofen and tetrazepam are detected via UV detection at 220 and 228 nm, respectively. Separation is performed at 25 degrees C and at a separation voltage of 30 kV, with 15 mM borate buffer (pH 10.2) containing 40 mM sodium dodecylsulfate as the electrolyte solution. Under these conditions the analytes were separated in <11 min. Sulfamethazine is used as an internal standard. Prior to determination, the samples are purified and enriched by means of an extraction-preconcentration step with a preconditioned C18 cartridge and by eluting the compounds with methanol. Good linearity, accuracy, precision, robustness and solution stability were achieved for the technique. Detection limits of 200 microg L(-1) for ibuprofen and 300 microg L(-1) for tetrazepam were obtained. These analytes were then determined in real urine using the technique.

Enantioselective determination of ibuprofen in plasma by high-performance liquid chromatography–electrospray mass spectrometry

The enantioselective analysis of ibuprofen (IBU), a chiral nonsteroidal anti-inflammatory drug, in human plasma was carried out by high-performance liquid chromatography (HPLC)-mass spectrometry (LC-MS-MS). The plasma samples were prepared by liquid-liquid extraction using hexane:ethyl acetate (8:2, v/v). The HPLC chiral resolution of IBU was obtained using a chiral stationary phase based on a tris-(3,5-dimethylphenylcarbamate) amylose derivative, under reversed phase conditions (CHIRALPAK AD-RH column), using a mobile phase consisting of methanol:water (8:2, v/v), containing 0.1% of an aqueous solution of phosphoric acid at pH 2, at a flow rate of 0.6 ml/min. A make-up liquid of 4.5% (w/v) NH(4)OH aqueous solution was used to assure optimum electrospray ionization in the negative mode. The coefficients of variation and deviation from nominal values were lower than 15% for both within- and between-day assays. The quantitation limit was 0.12 microg/ml and the linear range was 0.12-90.0 microg/ml for both enantiomers. The method proved to be suitable for single dose pharmacokinetic studies.

Influence of age on the enantiomeric disposition of ibuprofen in healthy volunteers

AIMS

To determine the influence of age on the enantioselective disposition of ibuprofen in humans.

METHODS

Healthy young (n = 16; aged 20-36 years) and elderly (n = 16; aged 66-84 years) volunteers were given a 400-mg oral dose of racemic ibuprofen, and blood and urine samples were collected for 24 h post drug administration. Serum concentrations, total and free, and urinary excretion of both enantiomers of ibuprofen together with the urinary excretion of the stereoisomers of the two major metabolites of the drug, both free and conjugated, were determined by high-performance liquid chromatography.

RESULTS

Ageing had little effect on the distribution and metabolism of R-ibuprofen, unbound clearance of the R-enantiomer via inversion being approximately two-fold that via noninversion mechanisms in both age groups. In contrast, the free fraction of S-ibuprofen was significantly greater [33%; young 0.48 +/- 0.10%; elderly 0.64 +/- 0.20%] mean difference -0.16; 95% confidence interval (CI) -0.05, -0.27; P < 0.01; and the unbound clearance of the drug enantiomer was significantly lower (28%; young 15.9 +/- 2.2 l min-1; elderly 11.5 +/- 4.1 l min-1; mean difference 4.4; 95% CI 2.12, 6.68; P < 0.001) in the elderly. The metabolite formation clearances of S-ibuprofen via glucuronidation, and oxidation at the 2- and 3- positions of the isobutyl side chain decreased by 24, 28 and 30%, respectively, in the elderly compared with the young, the differences between the two age groups being significant in each case (P < 0.05).

CONCLUSIONS

Following administration of racemic ibuprofen age-associated stereoselective alterations in drug disposition have been observed, with the elderly having increased free concentrations and lower unbound clearance of the S-enantiomer in comparison with the young. In contrast, the handling of the R-enantiomer is essentially unaltered with age. The results of this study indicate that the elderly have an increased exposure to the active ibuprofen enantiomer and thus some caution may be required when using this drug in this age group.

Resolution of chiral drugs by liquid chromatography based upon diastereomer formation with chiral derivatization reagents

Chiral derivatization reagents for resolution of biologically important compounds, such as chiral drugs by high-performance liquid chromatography (HPLC), based upon pre-column derivatization and diastereomer formation, are reviewed. The derivatization reagents for various functional groups, i.e., amine, carboxyl, carbonyl, hydroxyl and thiol, are evaluated in terms of reactivity, stability, wavelength, handling, versatility, sensitivity, and selectivity. The applicability of the reagents to the analyses of drugs and bioactive compounds are included in the text.

Enantioselective analysis of ibuprofen in human plasma by anionic cyclodextrin-modified electrokinetic chromatography

This paper reports the development of a rapid method for the enantioselective analysis of the nonsteroidal anti-inflammatory drug ibuprofen in human plasma by capillary electrophoresis employing the anionic cyclodextrin-modified electrokinetic chromatography mode. Sample cleanup was carried out by acidification with HCl followed by liquid-liquid extraction with hexane:isopropanol (99:1 v/v). The complete enantioselective analysis was performed within 10 min, using 100 mmol L(-1) phosphoric acid/triethanolamine buffer, pH 2.6, containing 2.0% w/v sulfated beta-cyclodextrin as chiral selector; fenoprofen, another nonsteroidal anti-inflammatory drug, was used as internal standard. The calibration curves were linear over the concentration range of 0.25-125.0 microg mL(-1) for each enantiomer of ibuprofen. The mean recoveries for ibuprofen enantiomers were up to 85%. The enantiomers studied could be quantified at three different concentrations (0.5, 5.0 and 50.0 microg mL(-1)) with a coefficient of variation and relative error not higher than 15%. The quantitation limit was 0.2 microg mL(-1) for (+)-(S)- and (-)-(R)-ibuprofen using 1 mL of human plasma. The plasma endogenous compounds and other drugs did not interfere with the present assay. The analysis of real plasma samples obtained from a healthy volunteer after administration of 600 mg of racemic ibuprofen showed a maximum plasma level of 29.6 and 39.9 microg mL(-1) of (-)-(R)- and (+)-(S)-ibuprofen, respectively, and the area under plasma concentration-time curve AUC(0-infinity) (+)-(S)/AUC(0-infinity) (-)-(R) ratio was 1.87.

Pharmaceutical and biomedical applications of enantioseparations using liquid chromatographic techniques

The chiral separation methods using liquid chromatographic techniques can be divided into two categories: one is a direct method, which is based on a diastereomer formation on stationary phase or in mobile phase. The other is an indirect method, which is based on a diasteromer formation by reaction with a homochiral reagent. The enantiomer separation on a chiral stationary phases followed by derivatization with an achiral reagent is also dealt with this review article as the indirect method. The pharmaceutical and biomedical applications of enantioseparations using the direct and indirect methods have been considered in this review.

High-performance liquid chromatography with a column-switching system and capillary electrophoresis for the determination of ibuprofen in plasma

Quantitative aspects of high-performance liquid chromatography with a column-switching system (CSS-HPLC) and capillary electrophoresis (CE) were investigated for the determination of ibuprofen in plasma. For CSS-HPLC, 100 microl of plasma was directly injected onto the column system for the three separation steps: (1) deproteinization and fractionation of plasma samples with a polymer-coated mixed-function phase column, (2) concentration with an intermediate column and (3) final separation with a main column. For CE, a mixture of 50 microl of plasma and 1 ml of acetonitrile was centrifuged and the supernatant was introduced onto the capillary (66 cmX50 microm I.D.; 62 cm to detector) at 20 degrees C. Run buffer was 250 mM sodium borate buffer (pH 8.5) and applied electric field was 379 V cm(-1). Linear dynamic ranges were 0.1-250 microg ml(-1) in CSS-HPLC and 1-1000 microg ml(-1) in CE. Intra-day and inter-day coefficients of variation were less than 5.6% and 6.5% for CSS-HPLC, 6.3% and 6.5% for CE, respectively. The limits of detection (S/N=3) for CSS-HPLC and CE were 25 ng ml(-1) and 300 ng ml(-1), respectively. CSS-HPLC was superior in simplicity and sensitivity, while CE was better in efficiency, rapidity, and cost.