The development and cross-validation of methods based on radioimmunoassay and LC/MS-MS for the quantification of the class III antiarrhythmic agent, MK-0499, in human plasma and urine

Paper-based sample processing for the fast and direct MS analysis of multiple analytes from serum samples

The direct MS detection of amino acids obtained from serum was successfully demonstrated via a paper-based fast electrokinetic sample clean-up method.

QT PRODACT: Comparison of Non-clinical Studies for Drug-Induced Delay in Ventricular Repolarization and Their Role in Safety Evaluation in Humans

Drug concentrations that would prolong repolarization parameters by 10%, including action potential duration (APD90, APD30-90), in in vitro assays using guinea-pig papillary muscle and QTc intervals in in vivo assays using conscious dogs, conscious monkeys, and anesthetized dogs were compared. Although, both the in vitro and in vivo assays showed concentration-dependent responses for compounds that have been classified as torsadogenic in humans, only a weak correlation in EC10 values was observed between the in vitro and in vivo assays. Among the in vivo QT assays, the EC10 values obtained from conscious dogs, conscious monkeys, and anesthetized dogs correlated well with each other, but the EC10 values in monkeys were somewhat lower in comparison to those in dogs. When in vivo QT assay EC10 values were compared to the respective human effective therapeutic plasma concentration (ETPC), the ratios of EC10 values to ETPCs were less than 20 for most torsadogenic compounds. In conclusion, the relationships between the extent of QTc interval prolongation and the concentration of drugs was highly consistent among the three in vivo models, suggesting that the ratios of EC10 values in in vivo QT assays are useful for estimating the safety margin of drugs that prolong the QTc interval.

Determination of gatifloxacin in human plasma by liquid chromatography/electrospray tandem mass spectrometry

Gatifloxacin is an advanced-generation, 8-methoxyfluoroquinolone that is active against a broad spectrum of pathogens, including antiobiotic resistant Streptococcus pneumoniae. Development of a rapid, sensitive and selective method for the determination of gatifloxacin in human plasma is essential for understanding the pharmacokinetics of the drug when administered orally or intravenously. Solid phase extraction (SPE) using Oasis HLB was used to extract gatifloxacin and the internal standard ciprofloxacin from plasma. A method based on liquid chromatography/electrospray tandem mass spectrometry (LC/ESI-MS/MS) was developed and validated to quantitate gatifloxacin in human plasma. The precursor and major product ions of the analyte were monitored on a triple quadrupole mass spectrometer with positive ion electrospray ionization (ESI) in the multiple reaction monitoring (MRM) mode. Mechanisms for the formation of collision-induced dissociation products of gatifloxacin are proposed. Linear calibration curves were generated from 10--1000 ng/mL with coefficients of determination greater than 0.99. The interday and intraday precision (%RSD) was less than 6.0% and accuracy (%error) was less than 5.4% for gatifloxacin. The limit of detection (LOD) for the method was 500 pg/mL based on a signal-to-noise ratio of 3.

Development of a method for rapid quantitation of amino acids by liquid chromatography-tandem mass spectrometry (LC-MSMS) in plasma

A new analytical method has been developed and is proposed for the rapid determination of eighteen common amino acids, including tryptophan, in plasma and dried blood spots, by liquid chromatography coupled with ionspray tandem mass spectrometry. Potentially the method can include other amino acids and can be used for the diagnosis of metabolic disease. The use of the ionspray tandem mass spectrometry approach permits extremely rapid chromatographic separation of all amino acids requiring less than four minutes for the analysis of each sample, after a simple sample preparation procedure. The chromatographic separation of the analytes was achieved using a CN normal phase column and a water/acetonitrile/trifluoroacetic acid mobile phase at flow rate of 1 ml/min. The mass spectrometer was operated in multiple reaction monitoring mode, where each analyte had its own unique precursor and product ion setting. The quantitative analysis of amino acids was achieved using as internal standards just two representative isotopically labeled amino acids: D4-Ala and D5-Phe. Calibration is made externally by using aqueous solutions with the same labelled amino acids as internal standards. The high specificity of tandem mass spectrometry coupled with a fast chromatographic process is suitable for the rapid and reliable assay of metabolically significant amino acids. The liquid chromatography-tandem mass spectrometry method is more effective than other published tandem mass spectrometry methods at distinguishing isobaric amino acids like Leu, Ile and HO-Pro and certainly far more rapid than HPLC or ion-exchange chromatographic methods.

Determination of antimigraine compounds rizatriptan, zolmitriptan, naratriptan and sumatriptan in human serum by liquid chromatography/electrospray tandem mass spectrometry

Development of a rapid, sensitive and selective method for the determination of antimigraine drugs from human serum is essential for understanding the pharmacokinetics of these drugs when administered concurrently. Solid phase extraction (SPE) using Oasis HLB was used to extract the drugs (sumatriptan, naratriptan, zolmitriptan and rizatriptan) and the internal standard bufotenine from serum. A method based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) was developed and validated to simultaneously quantitate these antimigraine drugs from human serum. The precursor and major product ions of the analytes were monitored on a triple quadrupole mass spectrometer with positive ion electrospray ionization (ESI) in the multiple reaction monitoring (MRM) mode. The base peak in all the analytes is formed by alpha cleavage associated with protonation of the secondary amine. Mechanisms for the formation of the collision-induced dissociation products of these antimigraine compounds are proposed. Linear calibration curves were generated from 1-100 ng/mL with all coefficients of determination greater than 0.99. The inter- and intraday precision (%RSD) were less than 9.3% and accuracy (%error) was less than 9.8% for all components. The limits of detection (LOD) for the method were 250 pg/mL for sumatriptan and 100 pg/mL for the remaining analytes based on a signal-to-noise ratio of 3.

Liquid chromatography-mass spectrometry in forensic and clinical toxicology

This paper reviews liquid chromatographic-mass spectrometric (LC-MS) procedures for the identification and/or quantification of drugs of abuse, therapeutic drugs, poisons and/or their metabolites in biosamples (whole blood, plasma, serum, urine, cerebrospinal fluid, vitreous humor, liver or hair) of humans or animals (cattle, dog, horse, mouse, pig or rat). Papers published from 1995 to early 1997, which are relevant to clinical toxicology, forensic toxicology, doping control or drug metabolism and pharmacokinetics, were taken into consideration. They cover the following analytes: amphetamines, cocaine, lysergide (LSD), opiates, anabolics, antihypertensives, benzodiazepines, cardiac glycosides, corticosteroids, immunosuppressants, neuroleptics, non-steroidal anti-inflammatory drugs (NSAID), opioids, quaternary amines, xanthins, biogenic poisons such as aconitines, aflatoxins, amanitins and nicotine, and pesticides. LC-MS interface types, mass spectral detection modes, sample preparation procedures and chromatographic systems applied in the reviewed papers are discussed. Basic information about the biosample assayed, work-up, LC column, mobile phase, interface type, mass spectral detection mode, and validation data of each procedure is summarized in tables. Examples of typical LC-MS applications are presented.

Stereoselectivity of antibodies for the bioanalysis of chiral drugs

The use of immunoassay techniques represents an alternative approach to the more common chromatographic methods for the determination of the concentrations of chiral drugs. In the development of the former technique, the inherent stereoselectivity of the antibodies used appears to be an important parameter to be studied. The structural features of the drug, including the environment around the asymmetric center, the flexibility of the molecule and the ability of the molecule to undergo racemization, contribute to the molecule's ability to be recognized by stereoselective antibodies. These parameters are intrinsic and can not be influenced by the investigator. On the other hand, other parameters can be modified to favor the raising of highly stereoselective antibodies. These include the synthesis of an appropriate hapten; the selection of an optimal spacer arm between the hapten and the carrier protein used for the immunization procedure; and the choice of appropriate immunization and antibody-screening procedures. The purification of antibodies using affinity chromatography may also facilitate the selection of stereoselective antibodies.

Determination of SR 49059 in human plasma and urine by LC-APCI/MS/MS

SR 49059 ((2S 1-[(2R 3S)-5-chloro-3-(2-chlorophenyl)-1-(3, 4-dimethoxybenzene-sulfonyl)-3-hydroxy-2,3-dihydro-1 H-indole-2-carbonyl]-pyrrolidine-2-carboxamide) is an orally active non-peptide vasopressin V1a antagonist. A sensitive, selective, and robust LC-MS/MS method was developed to determine the plasma and urine concentrations of SR 49059 in support of clinical studies. Plasma samples were prepared based on a rapid extraction procedure using Chem Elut cartridges. The extracted samples were analyzed on a C18 HPLC column interfaced with a Finnigan TSQ 700 mass spectrometer. Positive atmospheric chemical ionization (APCI) was employed as the ionization source. The analyte and its internal standard (2H6-SR 49059) were detected by use of multiple reaction monitoring (MRM) mode. The plasma matrix had a calibration range 0.2-20 ng ml-1, with within and between run accuracy and precision both less than 10%. The chromatographic run time was approximately 3 min. Urine samples were prepared based on a simple dilution with water, followed by analysis under the same conditions as plasma. The calibration range for urine matrix was 20-5000 ng ml-1, with within and between run accuracy and precision less than 11%. The method has been successfully applied to the clinical sample analysis. The plasma assay was also evaluated on a Finnigan TSQ 7000 mass spectrometer. The performance based on precision and accuracy was virtually identical to that on the TSQ 700, with the exception of linearity in calibration curve (the TSQ 700 was linear, the TSQ 7000 was quadratic).

Determination of ZD9583, a thromboxane receptor antagonist, in human plasma and urine by liquid chromatography atmospheric pressure chemical ionization tandem mass spectrometry

A liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI-MS-MS) method is described for the determination of a thromboxane receptor antagonist (4Z)-6-((2S,4S,5R)-2-(1-(2-cyano-4-methylphenoxy)-1-methylethyl)-4 -(3-pyridyl)-3-dioxan-5-yl)hex-4-enoic acid (ZD9583, I) in human plasma and urine. Proteins in plasma and urine samples are precipitated using acidified acetonitrile. The resulting supernatant is chromatographed on a C8 reversed-phase chromatography column. Following the diversion of the solvent front from the mass spectrometer by a switching valve, the column eluate is passed on to the mass spectrometer via a heated nebulizer interface where the analyte is detected by multiple reaction monitoring (MRM). The method has a chromatographic run time of less than 2 min, a linear calibration curve with a range of 1-500 ng ml(-1) and intra- and inter-day precision estimates of less than 10% over the calibration range.

A method using a liquid chromatographic-electrospray-mass spectrometric assay for the determination of antimigraine compounds: preliminary pharmacokinetics of MDL 74,721, sumatriptan and naratriptan, in rabbit

MDL 74,721 (I), sumatriptan(II) and naratriptan(III) are new 5-HT1-like agonists that have potential as a novel treatment for migraine. Liquid chromatographic-electrospray-mass spectrometric (LC-ESI-MS) assay have been developed to compare the pharmacokinetics of these three antimigraine compounds. The concentration of each parent drug was determined using a solid-phase extraction method and LC-ESI-MS analysis demonstrating the high sensitivity and specificity of the methods down to subnanogram levels in rabbit plasma samples. Pharmacokinetic parameters evaluated after administration of single intravenous and oral doses were very similar and the ANOVA analysis did not show any statistically significant differences for t1/2, Cmax, V or AUC (normalised). The pharmacokinetic parameters showed short t1/2 (range 1.14-1.9 h) either after intravenous (i.v.) or oral (p.o.) administration and high total body clearance (CL) after the p.o. dose both probably due to extensive and rapid metabolism of the parent drugs as suggested by the low values for bioavailability (range 13.4-22.8%).

Picogram determination of a novel dopamine D4 receptor antagonist in human plasma and urine by liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry

A sensitive and specific assay for the determination of 3-[[4-(4-chlorophenyl)piperazin-1-yl]methyl]-1H-pyrrolo[2,3-b]p yri dine (I, L-745,870), a potential antipsychotic agent, has been developed, utilizing high-performance liquid chromatography (HPLC) with tandem mass spectrometric (MS-MS) detection. The analyte and the internal standard (II, 3-[[4-(4-trifluoromethyl)piperazin-1-yl]methyl]-1H-pyrrolo[2,3-b] pyridine) were isolated from a basified biological matrix using liquid-liquid extraction with methyl-tert.-butyl ether. The organic extract was evaporated to dryness, the residue was reconstituted in a mobile phase and injected into the HPLC system. The chromatographic conditions used for the analysis were a Keystone Scientific C18 BDS 150 x 4.6 mm, 5 microns column with a mobile phase consisting of a 40:60 (v/v) mixture of acetonitrile and water containing 10 mM ammonium acetate and 0.1% formic acid pumped at a flow-rate of 1.2 ml/min, yielding retention times of 3.4 and 5.0 min for I and II, respectively. The MS-MS detection was performed on a PE Sciex API III Plus tandem mass spectrometer using a heated nebulizer interface. Multiple reaction monitoring using the parent-->product ion combinations of m/z 327-->131 and 361-->131 were utilized to quantitate I and II, respectively. The assays were validated in the concentration range of 0.1 to 100 and 0.5 to 500 ng/ml for plasma and urine, respectively. The precision of the assays, expressed as coefficients of variation were less than 10% over the entire concentration range, with adequate assay accuracy, sensitivity and specificity to determine the pharmacokinetics in human subjects following a single 1-mg dose.

Use of LC-MS/MS to cross-validate a radioimmunoassay for the fibrinogen receptor antagonist, Aggrastat (tirofiban hydrochloride) in human plasma

A method based on LC-MS/MS was developed for the determination of the fibrinogen-receptor antagonist Aggrastat in human plasma. The drug is isolated from plasma by liquid extraction and converted into its N-trifluoroacetyl derivative prior to analysis by HPLC with atmospheric pressure negative chemical ionization MS/MS detection. A structural analog is used as the internal standard and the lower quantifiable limit of the assay is 0.4 ng ml-1 with a relative standard deviation of 7%. This assay was used to cross-validate the existing immunoassay by analysis of plasma from patients receiving the drug. The specificity of the immunoassay was thereby confirmed.

Radioimmunoassay and gas chromatography/mass spectrometry for a novel antiglaucoma medication of a prostaglandin derivative, S-1033, in plasma

A radioimmunoassay (RIA) and a gas chromatographic/mass spectrometric (GC/MS) method for a new antiglaucoma medicament, the prostaglandin derivative sodium (5Z, 9 alpha, 11 alpha, 13E)-9,11-dihydroxyprosta-5, 13-dienoate (S-1033), in human and rabbit plasma were investigated. For a competitive RIA, antisera from rabbit and radioiodine-labeled S-1033 were prepared by immunizing a conjugate of S-1033 with bovine serum albumin and by the Bolton and Hunter method, respectively. Pretreatment by C18 solid-phase extraction (SPE) for rabbit plasma sample and further purification by high-performance liquid chromatography (HPLC) for human plasma samples followed by the RIA (SPE/RIA and HPLC/RIA, respectively) were developed. The assay recoveries of SPE/RIA and HPLC/RIA were both excellent and the limits of quantitation were 320 and 10 pg ml-1, respectively. GC/MS for plasma samples after solid-phase extraction and thin-layer chromatographic purification was also developed using deuterium-labeled S-1033 as internal standard. The limit of quantitation was 100 pg ml-1 in human or rabbit plasma. Rabbit plasma samples after administration of this drug were measured by SPE/RIA and GC/MS and the assay results from both methods agreed well. The SPE/RIA, HPLC/RIA and GC/MS assay methods were suitable for measuring samples from preclinical studies, clinical studies and cross-validation, respectively.