Ibuprofen alters human testicular physiology to produce a state of compensated hypogonadism.

Concern has been raised over increased male reproductive disorders in the Western world, and the disruption of male endocrinology has been suggested to play a central role. Several studies have shown that mild analgesics exposure during fetal life is associated with antiandrogenic effects and congenital malformations, but the effects on the adult man remain largely unknown. Through a clinical trial with young men exposed to ibuprofen, we show that the analgesic resulted in the clinical condition named "compensated hypogonadism," a condition prevalent among elderly men and associated with reproductive and physical disorders. In the men, luteinizing hormone (LH) and ibuprofen plasma levels were positively correlated, and the testosterone/LH ratio decreased. Using adult testis explants exposed or not exposed to ibuprofen, we demonstrate that the endocrine capabilities from testicular Leydig and Sertoli cells, including testosterone production, were suppressed through transcriptional repression. This effect was also observed in a human steroidogenic cell line. Our data demonstrate that ibuprofen alters the endocrine system via selective transcriptional repression in the human testes, thereby inducing compensated hypogonadism.

Using the Absorption Cocktail Approach to Assess Differential Absorption Kinetics of Cannabidiol Administered in Lipid-Based Vehicles in Rats.

Lipid-based drug delivery systems have been vastly investigated as a pharmaceutical method to enhance oral absorption of lipophilic drugs. However, these vehicles not only affect drug bioavailability but may also have an impact on gastric emptying, drug disposition, lymphatic absorption and be affected by lipid digestion mechanisms. The work presented here compared the pharmacokinetic (PK) behavior of the non-intoxicating cannabinoid cannabidiol (CBD) in sesame oil vs. a self-nano emulsifying drug delivery system (SNEDDS). This investigation was conducted with a unique tool termed the "absorption cocktail approach". In this concept, selected molecules: metoprolol, THC, and ibuprofen, were coadministered with CBD in the SNEDDS and sesame oil. This method was used to shed light on the complex absorption process of poorly soluble drugs in vivo, specifically assessing the absorption kinetics of CBD. It was found that the concentration vs. time curve following CBD-sesame oil oral administration showed extended input of the drug with a delayed Tmax compared to CBD-SNEDDS. Using the "cocktail" approach, a unique finding was observed when the less lipophilic compounds (metoprolol and ibuprofen) exited the stomach much earlier than the lipophilic cannabinoids in sesame oil, proving differential absorption kinetics. Findings of the absorption cocktail approach reflected the physiological process of the GI, e.g., gastric retention, stomach content separation, lipid digestion, drug precipitation and more, demonstrating its utility. Nonetheless, the search for more compounds as suitable probes is underway.

Analgesic effectiveness, pharmacokinetics, and safety of a paracetamol/ibuprofen fixed-dose combination in children undergoing adenotonsillectomy: A randomized, single-blind, parallel group trial.

BACKGROUND: Pain following tonsillectomy is often poorly managed in the home setting. Multimodal analgesia with acetaminophen (paracetamol) and nonsteroidal anti-inflammatory drugs offers superior analgesia over monotherapy but may be difficult for caregivers to manage. A fixed-dose combination oral suspension product containing paracetamol and ibuprofen has been developed to facilitate pediatric dosing. AIMS: The aims of this study are to determine the analgesic effectiveness, pharmacokinetics, and safety of the fixed-dose combination at two doses in the pediatric population. METHODS: In this prospective, multicenter, randomized, single-blind, parallel group trial, 251 children aged 2-12 years undergoing day-stay (adeno)tonsillectomy were randomized to two dose groups of the fixed-dose combination. A doubled loading dose was given preoperatively, followed by treatment for up to 11 days (Higher dose: paracetamol 15 mg/kg + ibuprofen 4.5 mg/kg, Lower dose: paracetamol 12 mg/kg + ibuprofen 3.6 mg/kg). Blood samples were collected for pharmacokinetic analysis for up to 6 hours after the loading dose. The analgesic effectiveness was examined on the first day after surgery using both Parents Postoperative Pain Measurement and modified Wong-Baker Faces pain scales. Rescue medication consumption was recorded throughout the study. RESULTS: Differences in maximum plasma concentration (Cmax ) and total exposure (AUC0→t ) between the treatment groups for both analytes were consistent with a 25% increase in dose; there was no difference in time to peak concentration (Tmax ). On the first postoperative day, there was no difference in pain scores or rescue medication use between treatment groups (approximately 30% in both groups). The combination was well tolerated by both groups. The most common adverse events were vomiting and nausea. The incidence of postoperative bleeding was 4.4%. CONCLUSION: The shallow dose-response relationship and good tolerability of the fixed-dose combination over an extended study period supports the utility of both doses of the fixed-dose combination in the home setting.

Acetaminophen, ibuprofen, and tramadol analgesic interactions after adenotonsillectomy.

BACKGROUND: The impact of tramadol in children given acetaminophen-ibuprofen combination therapy is uncertain in acute pediatric pain management. A model describing the interaction between these three drugs would be useful to understand the role of supplemental analgesic therapy. METHODS: Children undergoing tonsillectomy were given oral paracetamol and ibuprofen perioperatively. Blood was taken for paracetamol and ibuprofen drug assay on up to six occasions over 6 h after the initial dose. Tramadol was administered by caregivers for unacceptable postoperative pain. Pain was measured using the Parent's Postoperative Pain Measurement rating two hourly on the first postoperative day. A first-order absorption, one-compartment linear model with first-order elimination was used to describe acetaminophen and ibuprofen disposition. Analgesia was described using an EMAX model extended for three drugs, assuming additive effects. Curve fitting was performed using nonlinear mixed effects models. RESULTS: Pharmacodynamic parameter estimates, expressed using fractional Hill equation, were maximum effect (EMAX ) 0.65 (95%CI 0.54, 0.74), the concentration of acetaminophen associated with 50% of the maximal drug effect (C50,ACET ) 7.06 (95%CI 7.03, 7.72) mg/L, and the ibuprofen C50 (C50,IBU ) 3.95 (95%CI 2.57, 7.53) mg/L. The Hill coefficient was 1.48 (95%CI 0.92, 2.62) and an interaction term was fixed at zero (additivity). The half-time (t1/2 keo) for equilibration between the plasma and effect site was 0.34 hour (95%CI 0.23, 1.98) for acetaminophen and 1.04 hour (95%CI 0.75, 1.77) for ibuprofen. Tramadol had a C50,TRAM of 0.07 (95%CI 0.048, 1.07) mg/L with a t1/2 keo,TRAM 1.78 hour (95%CI 1.06, 1.96). CONCLUSION: Ibuprofen has an EC50 for analgesia in children similar to that of adults (3.95 mg/L; 95%CI 2.57-7.53, vs 5-10 mg/L adults). The maximum effect from combination therapy (ie, 65% reduction in pain score) achieves satisfactory analgesia with commonly used doses but increased dose adds little additional benefit. The addition of tramadol to this analgesic mixture prolongs analgesia duration.

Stereoselective Pharmacokinetics and Chiral Inversion of Ibuprofen in Adjuvant-induced Arthritic Rats.

2-Arylpropionic acid (2-APA) nonsteroidal anti-inflammatory drugs are commonly used in racemic mixtures (rac) for clinical use. 2-APA undergoes unidirectional chiral inversion of the in vivo inactive R-enantiomer to the active S-enantiomer. Inflammation causes the reduction of metabolic activities of drug-metabolizing enzymes such as cytochrome P450 (P450) and UDP-glucuronosyltransferase. However, it is unclear whether inflammation affects the stereoselective pharmacokinetics and chiral inversion of 2-APA such as ibuprofen (IB). We examined the effects of inflammation on the pharmacokinetics of R-IB and S-IB after intravenous administration of rac-IB, R-IB, and S-IB to adjuvant-induced arthritic (AA) rats, an animal model of inflammation. The plasma protein binding of rac-IB, glucuronidation activities for R-IB and S-IB, and P450 contents of liver microsomes in AA rats were determined. Total clearance (CLtot) of IB significantly increased in AA rats, although the glucuronidation activities for IB, and P450 contents of liver microsomes decreased in AA rats. We presumed that the increased CLtot of IB in AA rats was caused by the elevated plasma unbound fraction of IB due to decreased plasma albumin levels in AA rats. Notably, CLtot of R-IB but not S-IB significantly increased in AA rats after intravenous administration of rac-IB. These results suggested that AA could affect drug efficacies after stereoselective changes in the pharmacokinetics of R-IB and S-IB.

Enantioselective analysis of ibuprofen enantiomers in mice plasma and tissues by high-performance liquid chromatography with fluorescence detection: Application to a pharmacokinetic study.

A direct fluorometric high-performance liquid chromatography (HPLC) method was developed and validated for the analysis of ibuprofen enantiomers in mouse plasma (100 µl) and tissues (brain, liver, kidneys) using liquid-liquid extraction and 4-tertbutylphenoxyacetic acid as an internal standard. Separation of enantiomers was accomplished in a Chiracel OJ-H chiral column based on cellulose tris(4-methylbenzoate) coated on 5 µm silica-gel, 250 x 4.6 mm at 22 °C with a mobile phase composed of n-hexane, 2-propanol, and trifluoroacetic acid that were delivered in gradient elution at a flow rate of 1 ml min-1 . A fluorometric detector was set at: λexcit . = 220 nm and λemis. = 290 nm. Method validation included the evaluation of the selectivity, linearity, lower limit of quantification (LLOQ), within-run and between-run precision and accuracy. The LLOQ for the two enantiomers was 0.125 µg ml-1 in plasma, 0.09 µg g-1 in brain, and 0.25 µg g-1 in for liver and kidney homogenates. The calibration curves showed good linearity in the ranges of each enantiomers: from 0.125 to 35 µg ml-1 for plasma, 0.09-1.44 µg g-1 for brain, and 0.25-20 µg g-1 for liver and kidney homogenates. The method was successfully applied to a pharmacokinetic study of ibuprofen enantiomers in mice treated i.v. with 10 mg kg-1 of racemate.

Fisher Discrimination of Metabolic Changes in Rats Treated with Aspirin and Ibuprofen.

BACKGROUND: Aspirin and ibuprofen are the most frequently prescribed non-steroidal anti-inflammatory drugs in the world. However, both are associated with a variety of toxicities. We applied serum metabonomics and Fisher discrimination for the early diagnosis of its toxic reaction in order to help diagnose these toxicities. METHODS: A total of 45 rats were randomly divided into Control group, Aspirin group, and Ibuprofen groups. The experiment groups were given intragastric aspirin (15 mg/kg) or ibuprofen (15 mg/kg) for 3 weeks. Liver function tests were performed and blood metabonomics were analyzed by gas chromatography-mass spectrometry. RESULTS: The most important compounds altered were trihydroxybutyric acid and l-alanine in the aspirin group, and acetoacetic acid, l-alanine, and trihydroxybutyric acid in the ibuprofen group. With respect to metabolic profiles, all 3 groups were completely distinct from one another. Fisher discrimination showed that 91.1% of the original grouped cases were correctly classified by the third week. However, only 55.6% of liver function tests were able to classify grouped cases correctly. CONCLUSION: Trihydroxybutyric acid, l-alanine, and acetoacetic acid were the most significant indicators of altered serum metabolites following intragastric administration of aspirin and ibuprofen in rates. These metabolomic data may be used for classification of aspirin and ibuprofen toxicity.

Bioanalytical method for the estimation of co-administered esomeprazole, leflunomide and ibuprofen in human plasma and in pharmaceutical dosage forms using micellar liquid chromatography.

The present study represents a connection between basic science and clinical applied science through providing a bioanalytical method for the analysis of certain co-administered drugs used for the treatment of rheumatoid arthritis. The studied drugs are esomeprazole, leflunomide and ibuprofen. The proposed bioanalytical method is a simple reversed phase high performance liquid chromatographic method using micellar mobile phase. The method is conducted using a Shim-pack VP-ODS (150 mm × 4.6 mm ID) stainless steel column at ambient temperature with ultraviolet detection at 285 nm. The micellar mobile phase consisted of 0.1 m sodium dodecyl sulfate, 10% n-propanol, 0.3% triethylamine in 0.02 m orthophosphoric acid (pH 3.5) and is pumped at a flow rate of 1.0 mL/min. The calibration curve was rectilinear over the concentration range of 0.1-5.0, 0.5-10.0 and 1.0-20.0 µg/mL for esomeprazole, leflunomide and ibuprofen respectively. The proposed method was successfully applied to the analysis of these drugs in dosage forms. The method is extended to the in-vitro, in-vivo determination of these drugs in spiked and real human plasma samples.

Simultaneous determination of ACE inhibitors and dexibuprofen in active pharmaceutical ingredient, formulations and human serum by RP-HPLC.

The contemporary work describes a rapid and cost effective reversed phase High Performance Liquid Chromatography (RP-HPLC) method for the quantification of Captopril, Lisinopril and Dexibuprofen (DXP) simultaneously in dosage formulations, active pharmaceutical ingredients and human serum. The chromatographic system included LC-20A pump, Sil-20A auto sampler and SPD-20A UV/visible detector. The estimation was carried out by using a C18 (5µm, 250 ×4.6 mm) column with mobile phase methanol: water (80:20 v/v, pH 3.0) at 230 nm with a flow rate of 1.0 ml•min-1. The retention time of Dexibuprofen was 5.4 min while that of Captopril and Lisinopril were found to be 3.2 and 1.8 minutes respectively. There was no considerable variation exists in between the tested drug spiked in serum and the extent recovered, without interference of serum in concurrent approximation. The method developed was found to be precise, selective and validated for precision, linearity, specificity, accuracy, limit of detection and limit of quantitation. There is no such method reported earlier for the determination of ACE Inhibitors and DXP simultaneously. The present study helps in assessing the co-administration of both drugs in treatment and can be employed for quality control analysis and drug-drug interaction studies.

Therapeutic drug monitoring in dried blood spots using liquid microjunction surface sampling and high resolution mass spectrometry.

Dried blood spots (DBS) are a versatile and stable tool for direct clinical blood analysis. Ambient high-resolution mass spectrometry is emerging as a method of choice for their quantitative analysis, for instance in therapeutic drug monitoring. Here, we coupled liquid microjunction surface sampling technology, a so-called Flowprobe, with an Orbitrap mass spectrometer and demonstrated the utility of this set-up for direct quantification of multiple drugs in DBS on filter paper. A three-layer set-up that we had introduced earlier enabled introduction of internal standards into DBS. We furthermore took an established point-of-care test system a step further and analyzed disposable test fields for blood glucose monitoring also for Flowprobe-based acetaminophen screening without additional sample preparation. Using as little as 2 µL blood, the method had an LOD of 1 µg mL(-1) (coefficient of variation of ≤15%) and acetaminophen recoveries of 82 to 119% for blinded samples, as assessed by LC-MS/MS. Half an hour after ingestions of a single 1000 mg acetaminophen dose, indistinguishable drug levels were measured in three healthy volunteers by LC-MS/MS and Flowprobe-Orbitrap MS analysis of DBS. Flowprobe analysis of DBS was 6- to 100-times more sensitive than corresponding desorption electrospray ionization MS analysis for four drugs. For instance, the LOD for salicylic acid analysis was 0.07 ng mL(-1) with Flowprobe measurement. Furthermore, we showed that multi-component analysis of five different substances, which may mimic polypharmacy in diabetes patients, in one blood sample for screening purposes was feasible. Taken together, our study suggests that microjunction surface sampling of DBS on filter paper and disposable point-of-care test fields may be developed into routine methods for near-patient multi-compound therapeutic drug monitoring that may advance blood screening analysis for patients with polypharmacy.

Impact of Chiral Bioanalytical Methods on the Bioequivalence of Ibuprofen Products Containing Ibuprofen Lysinate and Ibuprofen Base.

The purpose was to assess the impact of the use of a chiral bioanalytical method on the conclusions of a bioequivalence study that compared two ibuprofen suspensions with different rates of absorption. A comparison of the conclusion of bioequivalence between a chiral method and an achiral approach was made. Plasma concentrations of R-ibuprofen and S-ibuprofen were determined using a chiral bioanalytical method; bioequivalence was tested for R-ibuprofen and for S-ibuprofen separately and for the sum of both enantiomers as an approach for an achiral bioanalytical method. The 90% confidence interval (90% CI) that would have been obtained with an achiral bioanalytical method (90% CI: Cmax: 117.69-134.46; AUC0 (t) : 104.75-114.45) would have precluded the conclusion of bioequivalence. This conclusion cannot be generalized to the active enantiomer (90% CI: Cmax : 103.36-118.38; AUC0 (t) : 96.52-103.12), for which bioequivalence can be concluded, and/or the distomer (90% CI: Cmax : 132.97-151.33; AUC0 (t) : 115.91-135.77) for which a larger difference was observed. Chiral bioanalytical methods should be required when 1) the enantiomers exhibit different pharmacodynamics and 2) the exposure (AUC or Cmax ) ratio of enantiomers is modified by a difference in the rate of absorption. Furthermore, the bioequivalence conclusion should be based on all enantiomers, since the distomer(s) might not be completely inert, in contrast to what is required in the current regulatory guidelines. In those cases where it is unknown if the ratio between enantiomers is modified by changing the rate of absorption, chiral bioanalytical methods should be employed unless enantiomers exhibit the same pharmacodynamics. Chirality 28:429-433, 2016. © 2016 Wiley Periodicals, Inc.

Validated HPLC-UV method for determination of naproxen in human plasma with proven selectivity against ibuprofen and paracetamol.

Estimating the influence of interfering compounds present in the biological matrix on the determination of an analyte is one of the most important tasks during bioanalytical method development and validation. Interferences from endogenous components and, if necessary, from major metabolites as well as possible co-administered medications should be evaluated during a selectivity test. This paper describes a simple, rapid and cost-effective HPLC-UV method for the determination of naproxen in human plasma in the presence of two other analgesics, ibuprofen and paracetamol. Sample preparation is based on a simple liquid-liquid extraction procedure with a short, 5 s mixing time. Fenoprofen, which is characterized by a similar structure and properties to naproxen, was first used as the internal standard. The calibration curve is linear in the concentration range of 0.5-80.0 µg/mL, which is suitable for pharmacokinetic studies following a single 220 mg oral dose of naproxen sodium. The method was fully validated according to international guidelines and was successfully applied in a bioequivalence study in humans. Copyright © 2015 John Wiley & Sons, Ltd.

Comparison of Measured and Predicted Bioconcentration Estimates of Pharmaceuticals in Fish Plasma and Prediction of Chronic Risk.

Evaluation of the environmental risk of human pharmaceuticals is now a mandatory component in all new drug applications submitted for approval in EU. With >3000 drugs currently in use, it is not feasible to test each active ingredient, so prioritization is key. A recent review has listed nine prioritization approaches including the fish plasma model (FPM). The present paper focuses on comparison of measured and predicted fish plasma bioconcentration factors (BCFs) of four common over-the-counter/prescribed pharmaceuticals: norethindrone (NET), ibuprofen (IBU), verapamil (VER) and clozapine (CLZ). The measured data were obtained from the earlier published fish BCF studies. The measured BCF estimates of NET, IBU, VER and CLZ were 13.4, 1.4, 0.7 and 31.2, while the corresponding predicted BCFs (based log Kow at pH 7) were 19, 1.0, 7.6 and 30, respectively. These results indicate that the predicted BCFs matched well the measured values. The BCF estimates were used to calculate the human: fish plasma concentration ratios of each drug to predict potential risk to fish. The plasma ratio results show the following order of risk potential for fish: NET > CLZ > VER > IBU. The FPM has value in prioritizing pharmaceutical products for ecotoxicological assessments.

Ibuprofen lysinate, quicker and less variable: relative bioavailability compared to ibuprofen base in a pediatric suspension dosage form.

OBJECTIVES: To assess and compare the bioavailability of ibuprofen enantiomers (R and S) of two different pediatric suspensions: the first one with ibuprofen lysinate (Algidrin® Pediátrico, FARDI S.A., Barcelona, Spain) and the second one with ibuprofen base (Dalsy®, Abbott Laboratories S.A., Madrid, Spain). METHODS: A randomized, open-label, single-dose, balanced, crossover study under fasting conditions was performed at the CIM-Sant Pau. 24 healthy volunteers received a single dose of ibuprofen lysinate (Algidrin® Pediátrico, FARDI S.A.) and ibuprofen base (Dalsy®, Abbott Laboratories S.A.) equivalent to 400 mg of ibuprofen. 18 blood samples were drawn and ibuprofen enantiomer plasma concentrations were determined using an enantioselective analytical method. An analysis of variance (ANOVA) model was used, and the 90% confidence intervals (CI) were calculated; further analyses were made regarding rate of absorption and variability. RESULTS: The pharmacokinetic parameters (Algidrin® Pediátrico vs. Dalsy® (Mean±SD)) were: S-enantiomer: Cmax=22.39±5.33 vs. 19.97±3.19 µg/mL; AUC0t=74.83±16.69 vs. 74.64±14.80 µg×h/mL, and AUC0∞=77.46±19.33 vs. 76.98±17.13 µg×h/mL; and for R-enantiomer: Cmax=21.74±3.76 vs. 15.20±2.03 µg/mL; AUC0t=57.55±10.17 vs. 46.13±9.61 µg×h/mL, and AUC0∞ value was 58.49±10.57 vs. 47.03±10.02 µg×h/mL. The tmax (Median) for S-enantiomer (active) were: 0.5 vs. 1.33 hours (p=0.001) and for R-enantiomer: 0.5 vs. 1.0 hours (p=0.004). Ibuprofen pharmacokinetic values may vary under fed state and in pediatric population. CONCLUSIONS: While S-ibuprofen shows a similar bioavailability for AUC0t, AUC0∞, and Cmax, R-ibuprofen shows suprabioavailability for the lysinate formulation. The rate of absorption of the ibuprofen lysinate suspension is quicker and less variable than that of the ibuprofen base reference suspension and it exhibits a shorter tmax, which is of particular interest for achieving a rapid and homogeneous analgesic and antipyretic effect.

[Plasma ibuprofen enantiomers and their pharmacokinetics in Beagle dogs determined by HPLC].

A chiral high-performance liquid chromatography method was developed for the simultaneous determination of ibuprofen enantiomers in dog plasma. It was used to study the pharmacokinetics in the Beagle dog after intravenous administration of racemic-ibuprofen, S-ibuprofen and R-ibuprofen. Ketoprofen was chosen as the internal standard. After a simple precipitation using methanol as the precipitating solvent, both analytes and IS were separated on a Kromasil 100-5CHI-TBB chiral column (250 mm x4.6 mm, 5 µm) with isocratic elution using acetonitrile - 20 mmol x L(-1) phosphate buffer (pH 3.0, containing 5% methanol) (6 : 4) as the mobile phase. The detection wavelength was 220 nm. Liner calibration curves for both of the ibuprofen enantiomers were over the concentration range from 0.5 to 50 µg x mL(-1) with a lower limit of quantification of 0.5 µg x mL(-1), the accuracies were all in standard ranges. The intra- and inter- assay precisions were all below 7%. The recovery rate was 93.1% to 100.4%. The experiments proved that the method was simple, rapid and sensitive. It can be used in the quantitative determination of ibuprofen enantiomers in dog plasma. The method was used to determine the concentration of ibuprofen enantiomers in Beagle dog plasma after a single intravenous administration of racemic-ibuprofen, S-ibuprofen and R-ibuprofen (9 mg x kg(-1)) and the pharmacokinetics parameters were calculated based on the concentration-time curves. The C(max) of S-ibuprofen in Beagle dog plasma after a single intravenous administration of racemic-ibuprofen, S-ibuprofen and R-ibuprofen were 30.8 ± 4.7, 46.1 ± 5.9 and 20.0 ± 2.6 µg x mL(-1), respectively. In terms of the exposure of active ingredient, it revealed a significant difference between the administration of S-ibuprofen and the other two groups. The systematical R- to S- chiral inversion was discussed. Comparing the pharmacokinetic parameters at different doses, chiral inversion were 70.1% ± 36.6% and 76.4% ± 36.2%, respectively, after intravenous administration of racemic- and R-ibuprofen. This study provides a theoretical basis for the safety of ibuprofen formula of injection drug.

Simultaneous determination of methocarbamol and Ibuprofen by first derivative synchronous fluorescence spectroscopic method in their binary mixture and spiked human plasma.

Methocarbamol is formulated with Ibuprofen for treatment of alleviated pain associated with muscle spasm. This manuscript describes a sensitive and selective first derivative synchronous spectrofluorimetric method for simultaneous determination of both drugs. Factors affecting method selectivity were studied where best results were obtained upon using Δ λ = 20 and water as a solvent. Methocartbamol was determined at 283 nm while Ibuprofen at 285.5 nm in the concentration ranges of 0.4-5 and 0.2-4.8 µg/mL, respectively. The applicability of the proposed method was ascertained by application to different laboratory prepared mixtures and marketed formulation. The high sensitivity achieved by the proposed method permitted its application for determination of the drugs in human plasma spiked with pure drugs and their combined tablets. The proposed method showed no significant difference when compared with the reported HPLC method using student's t-test and F-ratio test.

Analysis of ibuprofen enantiomers in rat plasma by liquid chromatography with tandem mass spectrometry.

A sensitive and selective method for the analysis of ibuprofen enantiomers by LC-MS/MS was developed and validated for the purpose of application in pharmacokinetic studies in small experimental animals. Aliquots of 200 µL plasma were submitted to liquid-liquid extraction with hexane/diisopropylether (50:50 v/v) in acid pH. Separation was accomplished in a Chirex® 3005 (250 × 4.6 mm, 5 µm) column at 25°C with a mobile phase that consisted of 0.01 M ammonium acetate in methanol at a flow rate of 1.1 mL/min. The mass spectrometer consisted of an ESI interface operating at negative ionization mode and multiple reaction monitoring. The transitions 205 > 161 and 240 > 197 were monitored for ibuprofen enantiomers and fenoprofen (internal standard), respectively. Method validation included the evaluation of the matrix effect, stability, linearity, lower LOQ, within-run and between-run precision, and accuracy. The lower LOQ was 25 ng/mL for each ibuprofen enantiomer, and the calibration curves showed good linearity in the range 0.025-50 µg/mL. The method was successfully applied in the investigation of pharmacokinetic disposition of ibuprofen enantiomers in rats treated orally with 25 mg/kg of the racemate. Enantioselective kinetic disposition was observed with accumulation of (+)-(S)-ibuprofen in rats following single oral administration.

Determination of naproxen in human plasma by GC-MS.

This paper describes a GC-MS method for the determination of naproxen in human plasma. Naproxen and internal standard ibuprofen were extracted from plasma using a liquid-liquid extraction method. Derivatization was carried out using N-methyl-N-(trimethylsilyl)trifluoroacetamide. The calibration curve was linear between the concentration range of 0.10-5.0 µg/mL. Intra- and interday precision values for naproxen in plasma were <5.14, and accuracy (relative error) was better than 4.67%. The extraction recoveries of naproxen from human plasma were between 93.0 and 98.9%. The LOD and LOQ of naproxen were 0.03 and 0.10 µg/mL, respectively. Also, this assay was applied to determine the pharmacokinetic parameters of naproxen in six healthy Turkish volunteers who had been given 220 mg naproxen.

Determination of ibuprofen in human plasma and urine by gas chromatography/mass spectrometry.

This paper describes a GC/MS method for the determination of ibuprofen in human plasma and urine. Ibuprofen and internal standard naproxen were extracted from plasma and urine by using a liquid-liquid extraction method. Derivatization was carried out using N-methyl-N-(trimethylsilyl) trifluoroacetamide. Calibration curves were linear over the concentration range of 0.05-5.0 and 0.1-10.0 microg/mL for plasma and urine, respectively. Intraday and interday precision (RSD) values for ibuprofen in plasma and urine were less than 6.31%, and accuracy (relative error) was better than 12.00%. The mean recovery of ibuprofen was 89.53% for plasma and 93.73% for urine. The LOD was 0.015 and 0.03 microg/mL and the LOQ was 0.05 and 0.1 microg/mL for plasma and urine, respectively. The method was successfully applied to blood samples from three healthy male volunteers who had been given an oral tablet of 600 mg ibuprofen.

NMR spectroscopic approach reveals metabolic diversity of human blood plasma associated with protein-drug interaction.

Although blood plasma has been used to diagnose diseases and to evaluate physiological conditions, it is not easy to establish a global normal concentration range for the targeting components in the plasma due to the inherent metabolic diversity. We show here that NMR spectroscopy coupled with principal component analysis (PCA) may provide a useful method for quantitatively characterizing the metabolic diversity of human blood plasma. We analyzed 70 human blood plasma samples with and without addition of ibuprofen. By defining the PC score values as diversity index (I(div)) and the drug-induced PC score value change as interaction index (I(dist)), we find that the two indexes are highly correlated (P < 0.0001). Triglycerides, choline-containing phospholipids, lactate, and pyruvate are associated with both indexes (P < 0.0001), respectively. In addition, a significant amount of lactate and pyruvate are in the NMR "invisible" bound forms and can be replaced by ibuprofen. The diffusion and transverse relaxation time weighted NMR approaches gave rise to a better characterization of the diversity and the interaction than that of the one acquired using NOESYPR1D with 100 ms mixing time. These results might be useful for understanding the blood plasma-drug interaction and personalized therapy.