Stereospecific high-performance liquid chromatographic assay of ibuprofen: improved sensitivity and sample processing efficiency

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.

High-Throughput HPLC-MS/MS Method for Quantification of Ibuprofen Enantiomers in Human Plasma: Focus on Investigation of Metabolite Interference

In this research, as a part of the development of fast and reliable HPLC-MS/MS method for quantification of ibuprofen (IBP) enantiomers in human plasma, the possibility of IBP acylglucoronide (IBP-Glu) back-conversion was assessed. This involved investigation of in source and in vitro back-conversion. The separation of IBP enantiomers, its metabolite and rac-IBP-d3 (internal standard), was achieved within 6 min using Chiracel OJ-RH chromatographic column (150 × 2.1 mm, 5 μm). The followed selected reaction monitoring transitions for IBP-Glu (m/z 381.4 → 205.4, m/z 381.4 → 161.4 and m/z 205.4 → 161.4) implied that under the optimized electrospray ionization parameters, in source back-conversion of IBP-Glu was insignificant. The results obtained after liquid-liquid extraction of plasma samples spiked with IBP-Glu revealed that the amount of IBP enantiomers generated by IBP-Glu back-conversion was far <20% of lower limit of quantification sample. These results indicate that the presence of IBP-Glu in real samples will not affect the quantification of the IBP enantiomers; thereby reliability of the method was improved. Additional advantage of the method is the short analysis time making it suitable for the large number of samples. The method was fully validated according to the EMA guideline and was shown to meet all requirements to be applied in a pharmacokinetic study.

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.

Quantitation of ibuprofen in blood using gas chromatography-mass spectrometry (GC-MS)

Ibuprofen is a non-narcotic, non-steroidal anti-inflammatory drug used for the treatment of pain, fever, and inflammatory diseases such as rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis. It is also used for induction of closure of patent ductus arteriosus (PDA) in neonates. Although the exact mechanism of action of ibuprofen is not known, it is believed to mediate its therapeutic effects through the inhibition of cyclooxygenase and subsequently by the inhibition of prostacyclin production. As the drug has a number of side effects, which correlate to its circulating concentration, monitoring of ibuprofen in plasma or serum is desired for patients receiving high-dose therapy. Chromatographic methods are frequently used for the assay of ibuprofen, as no immunoassays are currently available.In the method described, the drug is extracted from the serum or plasma using methylene chloride and phosphate buffer (pH 6). Meclofenamic acid is used as an internal standard. The organic phase containing the drug is separated and dried under stream of nitrogen. After trimethylsilyl derivatization, analysis is done using gas-chromatography/ mass spectrometry (GC-MS). Quantification of the drug in a sample is achieved by comparing responses of the unknown sample to the responses of the calibrators using selected ion monitoring.

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.

Stereospecific high-performance liquid chromatographic analysis of ibuprofen in rat serum

A simple, rapid and sensitive high-performance liquid chromatographic method was developed for determination of ibuprofen, (+/-)-(R, S)-2-(4-isobutylphenyl)-propionic acid, enantiomers in rat serum. Serum (0.1 ml) was extracted with 2,2,4-trimethylpentane/isopropanol (95:5, v/v) after addition of the internal standard, (S)-naproxen, and acidification with H(2)SO(4). Enantiomeric resolution of ibuprofen was achieved on ChiralPak AD-RH column with ultraviolet (UV) detection at 220 nm without interference from endogenous co-extracted solutes. The calibration curve demonstrated excellent linearity between 0.1 and 50 microg/ml for each enantiomer. The mean extraction efficiency was >92%. Precision of the assay was within 11% (relative standard deviation (R.S.D.)) and bias of the assay was lower than 15% at the limit of quantitation (0.1 microg/ml). The assay was applied successfully to an oral pharmacokinetic study of ibuprofen in rats.

Validation of a liquid chromatographic method for the determination of ibuprofen in human plasma

A simple, rapid method of determining the ibuprofen concentration in small volumes of human plasma (50 microl) by HPLC was developed. The sample was prepared for injection using a solid-phase extraction method, with naproxen as the internal standard. A 96-well extraction plate was used, easing sample preparation and allowing the simultaneous extraction of multiple plasma samples directly into the HPLC injection vials. Samples were stable at room temperature for at least 48 h prior to injection. The HPLC method used an ultraviolet detector with a 5-min run time and measured concentrations across the range typically seen with the clinical use of this drug. The calibration curve was linear across the concentration range of 0.78-100 microg/ml with a limit of quantitation (LOQ) of 1.56 microg/ml. The coefficient of variation for intra-day and inter-day precision was 6% or less with accuracies within 2% of the nominal values for low (4.5 microg/ml), medium (40 microg/ml) and high (85 microg/ml) ibuprofen concentrations. For ibuprofen concentrations at the LOQ, the intra-day and inter-day precision and accuracy were within 10 and 15%, respectively. Recovery was 87% or greater for ibuprofen. This method was used to analyze plasma samples for unknown ibuprofen concentrations in bioequivalence and limited food effect studies of different formulations of ibuprofen. Thus, this method has been fully validated and used in the analysis of unknown plasma samples for ibuprofen.

Enhancement of ibuprofen dissolution via wet granulation with beta-cyclodextrin

The purpose was to investigate the effect of wet granulation with beta-cyclodextrin (betaCD) on the enhancement of ibuprofen (IBU) dissolution. The effect of the granulation variables on the physical properties as well as the dissolution of tablets prepared from these granules was also examined. Granulation was performed using three granulating solvents: water, ethanol (95 vol%), and isopropanol. Granules were either oven-dried for 2 h or air-dried for 3 days. The granules or respective physical mixtures were compressed into tablets. Powder X-ray diffraction showed that oven-dried granulation resulted in less amorphous entities thatfacilitated IBU-betaCD complexation in solution and enhanced the dissolution of the corresponding tablets compared to the physical mixture with or without oven drying. In contrast, air-dried granulation did not cause any differences in the X-ray diffraction pattern (crystallinity) or the dissolution compared to the physical mixture without drying. Isopropanol and water, as granulating solvents, enhanced the dissolution of the oven-dried batches more than ethanol. The Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) data showed that tablets prepared from oven-dried granules, but not air-dried granules, had lower AH values and percent loss in weight, respectively, than those prepared from the physical mixture as a result of the expulsion of the water molecules from the betaCD cavity and enhancement of the complexation in solution. These results showed that oven-dried granulation of IBU and betaCD provided faster IBU dissolution than the physical mixture; air-dried granulation did not substantially affect the dissolution of IBU.

Validation of a high-performance liquid chromatographic method for the determination of ibuprofen enantiomers in plasma of broiler chickens

To characterise the pharmacokinetic properties of each enantiomer of ibuprofen in broiler chickens, a stereospecific HPLC method based on a alpha1-acid glycoprotein bonded chiral stationary phase has been validated. S-(+)-naproxen was used as internal standard. Enantiomers of ibuprofen and S-(+)-naproxen were baseline separated using a mobile phase consisting of 0.1 M phosphate buffer pH = 7 and 0.4% 2-propanol. The method is precise, specific, accurate and reproducible. Recoveries were higher than 80% and the limits of quantification for R-(-)- and S-(+)-ibuprofen were 1.16 and 1.37 microg ml(-1), respectively. The method seemed suitable for the pharmacokinetic studies of ibuprofen in chickens.

Determination of Ibuprofen in human plasma by high-performance liquid chromatography: validation and application in pharmacokinetic study

A specific method for the simultaneous determination of S-(+)Ibuprofen and R-(-)Ibuprofen enantiomers in human plasma is described. Adopting a high-performance liquid chromatographic (HPLC) system with spectrofluorometer detector, the compounds were extracted from plasma in alcohol medium and were separated on C18 column, using a solution of acetonitrile-water-acetic acid-triethylamine as mobile phase. The limit of quantitation was 0.1 microg/mL for both compounds. The method was validated by intra-day assays at three concentration levels and was used in a kinetic study in healthy volunteers. During the study we carried out inter-day assays to confirm the feasibility of the method.

Direct resolution of optically active isomers on chiral packings containing ergoline skeleton. 6. Enantioseparation of profens

The enantioselective behaviour of some underivatized 2-arylpropionic acids (profens) and flobufen by HPLC using a terguride-based chiral stationary phase was tested. X-ray analysis of crystals of the chiral selector and its complexes with naproxen allowed a deeper insight into the enantiodiscriminative process. The column stability and reproducibility, and the potential of the packing for semipreparative scale separations were also determined. A method for determining flobufen enantiomers and metabolites in plasma samples is described.

Dissolution of ibuprofen enantiomers from coprecipitates and suspensions containing chiral excipients

The purpose of this research was to evaluate the stereospecific interaction of ibuprofen with chiral excipients such as hydroxypropyl-beta-cyclodextrin (HPCD), tartaric acid, sucrose, hydroxypropylmethylcellulose (HPMC), methylcellulose (MC), and a nonchiral excipient, citric acid. Coprecipitates of ibuprofen were prepared in molar ratios ranging between 1:0.5 and 1:10 by a solvent evaporation method and characterized using x-ray diffraction, Fourier-transform infrared (FTIR) spectroscopy, and dissolution testing. Phase solubility studies of ibuprofen were carried out by adding excess amount of ibuprofen to aqueous excipient solutions of varying concentrations. Interaction was studied in suspensions of ibuprofen with HPMC, MC, and sucrose stored at room temperature and 60 degrees C for 12 weeks. Solubility of ibuprofen in HPCD solutions increased 10-fold, whereas solubility decreased in the tartaric and citric acid solutions, a result of decreased pH with increased amount of the acids in which ibuprofen (pKa 4.8) is less soluble. Phase solubility diagrams of ibuprofen in aqueous HPCD, citric acid, and tartaric acid solutions showed no stereospecific differences in solubility of the two enantiomers. X-ray diffraction studies showed that ibuprofen exists in a crystalline form at low ibuprofen-to-excipient ratios, whereas at the higher ratios, it exists in an amorphous form. FTIR spectroscopy for HPCD coprecipitates showed a shift of the carbonyl stretching band of ibuprofen to a higher wavelength with a markedly decreased intensity, probably because of a breakdown in the intermolecular hydrogen bonding with ibuprofen and restriction of the drug molecule in the HPCD cavity, respectively. Dissolution profiles of the coprecipitates demonstrated higher dissolution rates than those of pure ibuprofen. The presence of chiral excipients did not appear to cause stereoselective release of the drug from the coprecipitates and the suspensions.

Resolution of enantiomers of ibuprofen by liquid chromatography: a review

Ibuprofen is one of the most effective and widely used non-steroidal analgesic and anti-inflammatory agent. It is marketed as a racemic mixture though it is known that the pharmacological activity resides in the (S)-(+)-enantiomer only. Several direct/indirect liquid chromatographic methods involving a variety of chiral/achiral phases along with their possible role in resolution, chiral and achiral agents used for derivatisation have been discussed with special reference to ibuprofen, and mentioning their application to the resolution of other 2-aryl-propionic acids/profens.

Comparative bioavailability study of codeine and ibuprofen after administration of the two products alone or in association to 24 healthy volunteers

The study objective was to compare the bioavailability of codeine and ibuprofen after oral administration of the two drugs alone or in association. The study was performed in three different periods, each separated by a wash-out of 6 days. Plasma concentrations were measured in 24 healthy volunteers after administration of a single oral dose of codeine phosphate (25 mg) and/or ibuprofen (200 mg). Codeine and ibuprofen assays were performed using two different HPLC methods. The relative bioavailabilities of codeine and ibuprofen (alone or in association) were 106 +/- 24% (mean +/- sd) and 101 +/- 19%, respectively. The results obtained demonstrated that bioavailabilities of codeine and ibuprofen were not modified when the two drugs were administrated alone or in association.

Stereoselective disposition of suspensions of conventional and wax-matrix sustained release ibuprofen microspheres in rats

PURPOSE

The aim of the study is to evaluate stereoselective in vivo disposition of suspensions of conventional and wax-matrix sustained release ibuprofen microspheres in rats.

METHODS

Male wistar rats were dosed i.v. with 20 mg/kg, or orally with conventional suspension, and three suspension formulations of sustained release microspheres (having three different particle sizes) of racemic ibuprofen. Blood samples were analyzed stereoselectively by reverse phase HPLC.

RESULTS

The mean Cmax for (S)- and (R)-ibuprofen decreased with increased particle size of the drug or microspheres in the suspension dosage forms, while the Tmax increased with increased particle size. The mean S/R ratio (AUC0-48) of the suspensions decreased with increase in particle size of the drug or microspheres and these ratios (for both conventional and sustained formulations) were higher than that of the i.v., an indication of presystemic inversion. Decrease in the ratios with increased particle size is suggestive of formulation dependent inversion. The plasma concentration-time data of the sustained release formulations showed bimodal profiles, irrespective of the particle size of the microspheres. The second peak observed after 8 hours is indicative of colonic absorption.

CONCLUSIONS

Stereoselective disposition of ibuprofen microspheres showed higher bioavailability compared to the conventional suspension. Bimodal disposition is influenced by dosage form while presystemic inversion is both site-specific, and dosage form dependent.

1-(5-Dimethylamino-1-naphthalenesulphonyl)-(S)-3-aminopyrrolidine (DNS-Apy) as a fluorescence chiral labelling reagent for carboxylic acid enantiomers

1-(5-Dimethylamino-1-naphthalenesulphonyl)-(S)-3-aminopyrrolidi ne (DNS-Apy) has been synthesized for the separation of carboxylic acid enantiomers by high-performance liquid chromatography (HPLC) and sensitive detection. The reagent reacts with carboxylic acids at room temperature in the presence of activation agents 2,2'-dipyridyl disulphide (DPDS) and triphenylphosphine (TPP). The maximum emission of the diastereomeric amide derived from (S)-phenylpropionic acid and ketoprofen derivatives of DNS-Apy was at 530 nm with excitation at 340 nm. The emission wavelength shifted towards the blue and the fluorescence intensities increased with increasing acetonitrile concentration in the medium. The diastereomers derived from anti-inflammatory drugs were efficiently resolved with a reverse-phase column using water:acetonitrile mixture as mobile phase. All of the racemate of arylpropionic acid derivatives gave equal fluorescence intensity of the two enantiomers with the exception of ketoprofen derivatives where the intensity of the first eluting enantiomer was half that of the second.

Methods of analysis of chiral non-steroidal anti-inflammatory drugs

Although the analysis of the enantiomers of chiral non-steroidal anti-inflammatory drugs (NSAIDs) has been carried out for over 20 years, there often remains a deficit within the pharmaceutical and medical sciences to address this issue. Hence, despite world-wide therapeutic use of chiral NSAIDs the importance of stereoselectivity in pharmacokinetic, pharmacodynamic and pharmacological activity and disposition has often been ignored. This review presents both the general principles that allow separation of chiral NSAID enantiomers, and discusses both the advantages and disadvantages of the available chromatographic assay methods and procedures used to separately quantify NSAID enantiomers in biological matrices.

Bioavailability and pharmacokinetics of ibuprofen in the broiler chicken

The intravenous, intramuscular and oral pharmacokinetics of ibuprofen in broiler chickens were investigated. In a preliminary study, plasma ibuprofen concentration-time profiles, following i.v. (25 mg/kg) dosing were best described by a 2-compartment model. After intravenous administration, the volume of distribution at steady-state (Vd(ss)), the total systemic clearance (ClB), the elimination half-life (t1/2 beta) and the MRT were 0.303 L/kg, 482.3 ml/h.kg, 2.71 h and 1.02 h, respectively. After intramuscular administration of ibuprofen, the tmax and Cmax were 0.37 h, and 42.2 micrograms/mL, respectively, with an estimated bioavailability of 46.7%. After oral administration of ibuprofen, the tmax and Cmax were 0.31 h and 23.91 micrograms/mL, respectively, with an estimated bioavailability of 24.2%. This is a preliminary study, examining the use of ibuprofen in broiler chickens, and should be followed by tissue residue and efficacy studies in different disease states.

Stereospecific high-performance liquid chromatographic assay of zopiclone in human plasma

A high-performance liquid chromatographic (HPLC) assay for the analysis of the enantiomers of zopiclone (ZPC), a cyclopyrrolone hypnotic, in plasma was developed. Following the addition of chlordiazepoxide as internal standard (I.S.), plasma containing the ZPC enantiomers and I.S. was extracted by liquid-liquid extraction at an alkaline pH. After evaporation of the organic layer, the drug and I.S. were reconstituted in ethanol-hexane (80:20, v/v) and injected onto the HPLC column. The enantiomers were separated at ambient temperature on a 25-cm Chiralcel OD-H column with ethanol-hexane (60:40, v/v) as the mobile phase pumped at a flow-rate of 0.6 ml/min. The enantiomers of ZPC were quantified by fluorescence detection with excitation and emission wavelengths of 300 and 470 nm, respectively. The assay described allows for the direct quantitation of ZPC without pre-column derivatization, and is suitable for clinical studies of ZPC in humans after administration of therapeutic doses.

Enantiospecific determination of ibuprofen in rat plasma using chiral fluorescence derivatization reagent, (-)-2-[4-(1-aminoethyl)phenyl]-6- methoxybenzoxazole

A highly sensitive and reversed-phase high-performance liquid chromatographic method for the determination of the enantiomeric composition of ibuprofen in rat plasma is described. The method is based on the resolution of the diastereomeric amides formed on reaction of the ibuprofen enantiomers with (-)-2-[4-(1-aminoethyl)phenyl]-6-methoxybenzoxazole ((-)-APMB) in the presence of 2,2'-dipyridyl disulphide (DPDS) and triphenylphosphine (TPP) in dichloromethane. The reaction mixture was allowed to stand at room temperature for 5 min, and the reaction was completed by evaporation with a stream of nitrogen at 40 degrees C. The minimum quantifiable concentrations were 0.2 microgram/mL and 0.4 microgram/mL for S-ibuprofen and R-ibuprofen, respectively, in a 10 microL injection volume. The method was applied to the determination of enantiomeric ibuprofen in plasma after oral administration to rats.