Stereoselective high-performance liquid chromatographic analysis of ketoprofen and its acyl glucuronides in chronic renal insufficiency

A new liquid phase microextraction method-based reverse micelle for analysis of dexketoprofen in human plasma by HPLC-DAD

A new liquid phase microextraction method was developed by used reverse micelle-based coacervates as microextraction agents for the separation of dexketoprofen (DKT) from human plasma before its determination by high-performance liquid chromatography with photodiode-array detection (HPLC-DAD). The change in the concentration of dexketoprofen in the plasma of the male and female patients was successfully monitored by using this method. The proposed method involves the use of reverse micelles of decanoic acid (DA) are dispersed in tetrahydrofuran (THF) and aqueous system. After addition of the DA and THF to the aqueous sample phase, the formation of micelles of nano and molecular size was observed in an ultrasonic bath. The solution was centrifuged, and the DKT extracted into the DA phase was analyzed by HPLC-DAD. Some analytical parameters that important in the developed procedure were examined in detail. The limit of detection (LOD), the limit of quantification (LOQ), the intraday, and inter day relative standard deviation (RSD, %) of the developed method in the plasma sample were found to be 12.8 ng mL−1, 38.8 ng mL−1, 1.7 and 3.9%, respectively. Additional/recovery studies were performed in plasma samples with proposed method, and quantitative recoveries were obtained in the range of 97–100%. The developed microextraction method was applied to human plasma that taken from volunteer patients for the determination of DKT.

Graphical abstract

Synthesis and characterization of bromophenol glucuronide and sulfate conjugates for their direct LC-MS/MS quantification in human urine as potential exposure markers for polybrominated diphenyl ethers

Bromophenol glucuronide and sulfate conjugates have been reported to be products of mammalian metabolism of polybrominated diphenyl ethers (PBDEs), a group of additive flame-retardants found ubiquitously in the environment. In order to explore their occurrence in human urine, four water-soluble bromophenol conjugates, namely, 2,4-dibromophenyl glucuronide, 2,4,6-tribromophenyl glucuronide, 2,4-dibromophenyl sulfate, and 2,4,6-tribromophenyl sulfate, were synthesized, purified, and characterized. An analytical protocol using solid-phase extraction and ion-paired liquid chromatography-electrospray tandem mass spectrometry (LC-ESI-MS/MS) quantification has been developed for the direct and simultaneous determination of these glucuronide and sulfate conjugates in human urine samples. The limit of detections for all analytes were below 13 pg mL(-1), with 73-101% analyte recovery and 7.2-8.6% repeatability. The method was applied to analyze 20 human urine samples collected randomly from voluntary donors in Hong Kong SAR, China. All the samples were found to contain one or more of the bromophenol conjugates, with concentration ranging from 0.13-2.45 μg g(-1) creatinine. To the best of our knowledge, this is the first analytical protocol for the direct and simultaneous monitoring of these potential phase II metabolites of PBDEs in human urine. Our results have also suggested the potential of these bromophenol conjugates in human urine to be convenient molecular markers for the quantification of population exposure to PBDEs.

Chiral separation of ketoprofen on an achiral C8 column by HPLC using norvancomycin as chiral mobile phase additives

A high-performance liquid chromatographic method for chiral separation of ketoprofen racemate was developed. (R)- and (S)-ketoprofen enantiomers were separated on a Hypersil BDS C8 column (150 mm x 4.6 mm i.d., 5 microm) at 25 degrees C, using acetonitrile-triethylamine acetate (TEAA) buffer (pH 5.2, 20 mM) (35:65, v/v) containing 2.0 mM norvancomycin as the mobile phase. Effects of norvancomycin concentration, content of acetonitrile and TEAA buffer pH on the enantioseparation were investigated. The method was validated for linearity, repeatability, limits of detection (LOD) and limits of quantification (LOQ). Calibration curves (r2 = 0.999) were constructed in the range of 2.01-200.8 microg ml(-1) for (S)-ketoprofen and 2.04-152.4 microg ml(-1) for (R)-ketoprofen, respectively. Repeatability (n = 5) showed less than 2% relative standard deviation (R.S.D.). LOD and LOQ for the two enantiomers were found to be 0.20 and 0.78 ng for (S)-ketoprofen, 0.20 and 0.86 ng for (R)-ketoprofen, respectively. Norvancomycin and vancomycin as chiral mobile phase additives (CMPAs) in the chiral separation showed similar abilities of enantioseparation. However, to obtain the optimum enantioseparation, a lower concentration of norvancomycin than that of vancomycin is required.

Glucuronidation in therapeutic drug monitoring

BACKGROUND

Glucuronidation is a major drug-metabolizing reaction in humans. A pharmacological effect of glucuronide metabolites is frequently neglected and the value of therapeutic drug monitoring has been questioned. However, this may not always be true.

METHODS

In this review the impact of glucuronidation on therapeutic drug monitoring has been evaluated on the basis of a literature search and experience from the own laboratory.

RESULTS

The potential role of monitoring glucuronide metabolite concentrations to optimize therapeutic outcome is addressed on the basis of selected examples of drugs which are metabolized to biologically active/reactive glucuronides. Furthermore indirect effects of glucuronide metabolites on parent drug pharmacokinetics are presented. In addition, factors that may modulate the disposition of these metabolites (e.g. genetic polymorphisms, disease processes, age, and drug-drug interactions) are briefly mentioned and their relevance for the clinical situation is critically discussed.

CONCLUSION

Glucuronide metabolites can have indirect as well as direct pharmacological or toxicological effects. Although convincing evidence to support the introduction of glucuronide monitoring into clinical practice is currently missing, measurement of glucuronide concentrations may be advantageous in specific situations. If the glucuronide metabolite has an indirect effect on the pharmacokinetics of the parent compound, monitoring of the parent drug may be considered. Furthermore pharmacogenetic approaches considering uridine diphosphate (UDP) glucuronosyltransferases polymorphisms may become useful in the future to optimize therapy with drugs subject to glucuronidation.

Enantioseparation of flurbiprofen and ketoprofen in patches and in urine excretions by achiral gas chromatography

The enantiomeric composition tests on flurbiprofen and ketoprofen present in patch products and in urine excretions following patch applications were performed as diastereomeric (R)-(+)-1-phenylethylamides by achiral gas chromatography and by gas chromatography-mass spectrometry in selected ion monitoring mode. The method for determination of (R)- and (S)-enantiomers in the range from 0.1 to 5.0 microg was linear (r > or = 0.9996) with acceptable precision (% RSD < or = 5.2) and accuracy (% RE = 0.6 approximately -2.4). The enantiomeric compositions of flurbiprofen in one patch product and of ketoprofen in five different products were identified to be racemic with relatively good precision (< or = 6.4%). The urinary excretion level of (R)-flurbiprofen was two times higher than its antipode, while the comparable excretion levels of (R)- and (S)-enantiomers for ketoprofen were observed.

Voltammetric studies and assay of the anti-inflammatory drug ketoprofen in pharmaceutical formulation and human plasma at a mercury electrode

The electrochemical reduction of the anti-inflammatory drug ketoprofen was studied in a Britton-Robinson (B-R.) buffer series of pH 2–11 using dc-polarography, cyclic voltammetry, and coulometry techniques. The electrode reaction pathway of the drug at the dropping mercury electrode was proposed and discussed. A new adsorptive cathodic stripping square-wave voltammetric procedure was optimized for the assay of bulk drug in a B-R. buffer of pH 2.0. The peak current was linear with the drug concentration over the ranges 2 × 10–9 to 2 × 10–7 M of the bulk drug, using a 60 s accumulation time period at –0.6 V (vs. Ag/AgCl/KCls). The percentage recovery of the bulk drug was 99.57 ± 0.54 and a detection limit of 0.10 ng mL–1 was achieved. The proposed procedure was successfully applied for the assay of ketoprofen in pharmaceutical formulation (Ketofan®) and human plasma. The percentage recoveries were 99.66 ± 0.47 and 101.76 ± 0.64 in pharmaceutical formulation and human plasma, respectively. A detection limit of 0.14 ng mL–1 plasma was achieved which was below that reported in literature using the different analytical techniques.Key words: ketoprofen (Ketofan®) determination, polarography, cyclic voltammetry, adsorptive cathodic stripping square-wave voltammetry, human plasma.

Acyl glucuronide drug metabolites: toxicological and analytical implications

Although glucuronidation is generally considered a detoxification route of drug metabolism, the chemical reactivity of acyl glucuronides has been linked with the toxic properties of drugs that contain carboxylic acid moieties. It is now well documented that such metabolites can reach appreciable concentrations in blood. Furthermore, they are labile, undergo hydrolysis and pH-dependent intramolecular acyl migration to isomeric conjugates of glucuronic acid, and may react irreversibly with plasma proteins, tissue proteins, and with nucleic acids. This stable binding causes chemical alterations that are thought to contribute to drug toxicity either through changes in the functional properties of the modified molecules or through antigen formation with subsequent hypersensitivity and other immune reactions. Whereas in vitro data on the toxicity of acyl glucuronides have steadily accumulated, direct evidence for their toxicity in vivo is scarce. Acyl glucuronides display limited stability, which is dependent on pH, temperature, nature of the aglycon, and so on. Therefore, careful sample collection, handling, and storage procedures are critical to ensure generation of reliable pharmacologic and toxicologic data during clinical studies. Acyl glucuronides can be directly quantified in biologic specimens using chromatographic procedures. Their adducts with plasma or cell proteins can be determined after electrophoretic separation, followed by blotting. ELISA techniques have been used to assess the presence of antibodies against acyl glucuronide-protein adducts. This review summarizes the most recent evidence concerning biologic and toxicologic effects of acyl glucuronide metabolites of various drugs and discusses their relevance for drug monitoring. A critical evaluation of the available methodology is included.

Resolution of enantiomers of ketoprofen by HPLC: a review

Today, a heightened awareness of the applicability of enantiomers in medicine and clinical practice has been gene-rated due to the continuous evolvement of the field of chirality. In this context, this article provides a review of separation of ketoprofen, an important drug, in a popular class of non-steroidal anti-inflammatory drugs (i.e. profens). This review highlights various methodologies, logistical considerations for separation and provides an exhaustive list of applications mainly focusing on the pharmacokinetic aspects. Clearly, the application of enantioselective methods for drug racemates paves the way to understand the in vivo behavior of individual enantiomer and hence an opportunity for an alternate and/or better option for treating the disease.

Clinical Pharmacokinetics of Dexketoprofen

Dexketoprofen trometamol is a water-soluble salt of the dextrorotatory enantiomer of the nonsteroidal anti-inflammatory drug (NSAID) ketoprofen. Racemic ketoprofen is used as an analgesic and an anti-inflammatory agent, and is one of the most potent in vitro inhibitors of prostaglandin synthesis. This effect is due to the (S)-(+)-enantiomer (dexketoprofen), while the (R)-(-)-enantiomer is devoid of such activity. The racemic ketoprofen exhibits little stereoselectivity in its pharmacokinetics. Relative bioavailability of oral dexketoprofen (12.5 and 25mg, respectively) is similar to that of oral racemic ketoprofen (25 and 50mg, respectively), as measured in all cases by the area under the concentration-time curve values for (S)-(+)-ketoprofen. Dexketoprofen trometamol, given as a tablet, is rapidly absorbed, with a time to maximum plasma concentration (tmax) of between 0.25 and 0.75 hours, whereas the tmax for the (S)-(+)-enantiomer after the racemic drug, administered as tablets or capsules prepared with the free acid, is between 0.5 and 3 hours. The drug does not accumulate significantly when administered as 25mg of free acid 3 times daily. The profile of absorption is changed when dexketoprofen is ingested with food, reducing both the rate of absorption (tmax) and the maximal plasma concentration. Dexketoprofen is strongly bound to plasma proteins, particularly albumin. The disposition of ketoprofen in synovial fluid does not appear to be stereoselective. Dexketoprofen trometamol is not involved in the accumulation of xenobiotics in fat tissues. It is eliminated following extensive biotransformation to inactive glucuroconjugated metabolites. No (R)-(-)-ketoprofen is found in the urine after administration of dexketoprofen, confirming the absence of bioinversion of the (S)-(+)-enantiomer in humans. Conjugates are excreted in urine, and virtually no drug is eliminated unchanged. The analgesic efficacy of the oral pure (S)-(+)-enantiomer is roughly similar to that observed after double dosages of the racemic compound. At doses above 7mg, dexketoprofen was significantly superior to placebo in patients with moderate to severe pain. A dose-response relationship between 12.5 and 25mg could be seen in the time-effects curves, the superiority of the 25mg dose being more a result of an extended duration of action than of an increase in peak analgesic effect. A plateau in the analgesic activity of dexketoprofen trometamol at the 25mg dose is suggested. The time to onset of pain relief appeared to be shorter in patients treated with dexketoprofen trometamol. The drug was well tolerated.

Determination of (R)- and (S)-ketoprofen in human plasma by liquid chromatography/tandem mass spectrometry following automated solid-phase extraction in the 96-well format

A sensitive and selective method was developed for the determination of (R)-ketoprofen ((R)-kt) and (S)-ketoprofen ((S)-kt) in human plasma using chiral liquid chromatography/tandem mass spectrometry (LC/MS/MS). Plasma samples spiked with stable-isotope-labeled [(13)C(1), (2)H(3)]-(R and S)-ketoprofen, for use as the internal standards, were prepared for analysis using automated solid-phase extraction (SPE) in the 96-well microtiter format. The enantiomers were separated on an (R)-1-naphthylglycine and 3,5-dinitrobenzoic acid (Chirex 3005) 250x2.0 mm i.d. analytical column, equipped with a 30x2.0 mm i.d. guard column using isocratic mobile phase conditions. The (R)- and (S)-kt levels were quantifiable from 0.05 to 2500 ng ml(-1) by constructing two separate curves from calibration standards covering the same range. The first curve ranged from 0.05 to 100 and the second from 100 to 2500 ng ml(-1). A concentration of 0.05 ng ml(-1) of either enantiomer was easily detected using a 1 ml plasma sample volume. The average method accuracy, evaluated at four levels over an extended period, was better than +/-3% over the entire range. The precision for the same set of quality control samples ranged from 4.0 to 7.0 % RSD (n = 24). The method was applied to the evaluation of pharmacokinetic parameters in human plasma obtained from volunteers who received 25 mg of kt by peroral administration of Actron caplets or by topical administration of Oruvail gel.

Stereoselective pharmacokinetics of ketoprofen and ketoprofen glucuronide in end-stage renal disease: evidence for a 'futile cycle' of elimination

AIMS

To assess if futile cycling of ketoprofen occurs in patients with decreased renal function.

METHODS

Ketoprofen was administered to six haemodialysis-dependent patients with end-stage renal disease as single (50 mg) or multiple doses (50 mg three times daily, for 7 days). Plasma and dialysate concentrations of the unconjugated and glucuronidated R- and S-enantiomers of ketoprofen were determined using h.p.l.c. following the single and multiple dosing.

RESULTS

The oral clearance was decreased and terminal elimination half-lives of R- and S-ketoprofen and the corresponding acyl glucuronides were increased in functionally anephric patients compared with healthy subjects. In contrast with the R-isomers, S-ketoprofen and S-ketoprofen glucuronide exhibited an unexpected accumulation (2.7-3. 8 fold) after repeated dosing achieving S:R ratios of 3.3+/-1.7 and 11.2+/-5.3, respectively. The plasma dialysis clearances for R- and S-ketoprofen glucuronides were 49.4+/-19.8 and 39.0+/-15.9 ml min-1, respectively, and 10.8+/-17.6 and 13.3+/-23.5 ml min-1 for unconjugated R- and S-ketoprofen.

CONCLUSIONS

The selective accumulation of S-ketoprofen and its acyl glucuronide are consistent with amplification of chiral inversion subsequent to futile cycling between R-ketoprofen and R-ketoprofen glucuronide. Severe renal insufficiency, and possibly more modest decrements, results in a disproportionate increase in systemic exposure to the S-enantiomer which inhibits both pathologic and homeostatic prostaglandin synthesis.

Pharmacokinetics and metabolism of ketoprofen after intravenous and intramuscular administration in camels

The pharmacokinetics of ketoprofen were determined after an intravenous (i.v.) and intramuscular (i.m.) dose of 2.0 mg/kg body weight in five camels (Camelus dromedarius) using gas chromatography/mass spectrometry (GC/MS). The data obtained (median and range) following i.v. administration was as follows: the elimination half-life (t(1/2beta)) was 4.16 (2.65-4.29) h, the steady state volume of distribution (Vss) was 130.2 (103.4-165.3) mL/kg, volume of distribution (area method) (Vd(area)) was 321.5 (211.4-371.0) mL/kg, total body clearance (Cl) was 1.00 (0.88-1.08) mL/min x kg and renal clearance was 0.01 (0.003-0.033) mL/min x kg. Following i.m. administration, the drug was rapidly absorbed with peak serum concentration of 12.2 (4.80-14.4) microg/mL at 1.50 (1.00-2.00) h. The systemic availability of ketoprofen was complete. The apparent half-life was 3.28 (2.56-4.14) h. A hydroxylated metabolite of ketoprofen was identified by (GC/MS) under electron impact (EI) and chemical ionization (CI) scan modes. The detection times for ketoprofen and hydroxy ketoprofen in urine after an intravenous (i.v.) dose of 3.0 mg/kg body weight was 24.00 and 70.00 h, respectively. Serum protein binding of ketoprofen at 20 microg/mL was extensive; (99.1+/-0.15%).

Glucuronic acid conjugates

The methods of assay in body fluids of 1-beta-alkyl, 1-beta-phenyl and 1-beta-acyl glucuronic acids ("glucuronide conjugates") have been reviewed. Most of the 78 references cited (from the literature of the period 1990-1997) concern the glucuronide conjugates of drug metabolites, and these have been considered, for reasons of accessibility, within sections of individual drug classes such as analgesics, anti-cancer agents and opioids. Other glucuronide conjugates are considered under "miscellaneous compounds". A few gas chromatography and capillary electrophoresis methods are described, but the major technique of assay (62 citations) is reversed-phase high-performance liquid chromatography.

Stereoselective pharmacokinetics and inversion of (R)- ketoprofen in healthy volunteers

The pharmacokinetics of ketoprofen enantiomers were evaluated after 25-, 50-, and 100-mg doses of (R)- ketoprofen and 100 mg of racemic ketoprofen in 25 healthy volunteers (12 male and 13 female). The fractional inversion (Finv) of (R)- ketoprofen was 8.9 +/- 3.3% using plasma data and 10.0 +/- 2.2% using urine data. There were small (< 5%) but significant differences between the enantiomers for areas under the plasma concentration-time curve (AUC) after the racemic dose (P < 0.005). Half-lives were 130-144 minutes for (R)- ketoprofen and 132-209 minutes for (S)- ketoprofen. Dose proportionality in AUC and maximum plasma concentration (Cmax) values was noted for both enantiomers. A total of 69% of the dose was recovered in the urine as (R)- and (S)- ketoprofen and conjugates. The elimination rate constant of (R)- ketoprofen was significantly different (P < 0.05) between men and women. Exposure to cyclooxygenase inhibiting (S)- ketoprofen was approximately 10% of the dose after the administration of pure (R)- ketoprofen and was independent of gender.

Quantification of ketoprofen enantiomers in human plasma based on solid-phase extraction and enantioselective column chromatography

An HPLC method for the quantification of ketoprofen enantiomers in human plasma is described. Following extraction with a disposable C18 solid-phase extraction column, separation of ketoprofen enantiomers and I.S. (3,4-dimethoxy benzoic acid) was achieved using a chiral column [Chirex 3005; (R)-1-naphthylglycine 3,5-dinitrobenzoic acid] with the mobile phase, 0.02 M ammonium acetate in methanol, set at a flow-rate of 1.2 ml/min. Baseline separation of ketoprofen enantiomers and I.S., free from interferences, was achieved in less than 20 min. The calibration curves (n = 14) were linear over the concentration range of 0.16 to 5.00 micrograms/ml per enantiomer [mean r2 of 0.999 for both enantiomers, root mean square error were 0.015 for R(-) and 0.013 for S(+)]. The inter-day coefficient of variation for duplicate analysis of spiked samples was less than 7% and the accuracy was more than 93% over the over the concentration range of 0.2 to 4.0 micrograms/ml for individual enantiomer using 1 ml of plasma sample. This method has been applied to a pharmacokinetic study from healthy human volunteers following the administration of a ketoprofen extended release product (200 mg). This method is simple, fast and should find wide application in monitoring pharmacokinetic studies of ketoprofen.