Rapid pharmacokinetic screening of salbutamol in plasma samples by column-switching high-performance liquid chromatography-electrospray mass spectrometry

The study of in vitro-in vivo correlation: pharmacokinetics and pharmacodynamics of albuterol dry powder inhalers

The pharmacokinetics and pharmacodynamics of albuterol were studied following inhalation of three different in-house dry powder formulations in healthy volunteers and in asthmatics. Albuterol in plasma was measured using liquid chromatography-mass spectrometry (LC-MS). The plasma concentration time profiles were fitted to a two-compartment model with first-order kinetics. Oral absorption of swallowed albuterol was eliminated by oral dosing of 560 mg activated charcoal 1 h prior to albuterol aerosol administration. The peak concentration was reached within 15-20 min. Mean peak concentrations in healthy volunteers (six males and six females) were 1.74 +/- 0.34, 2.01 +/- 0.35, and 2.59 +/- 0.27 ng/mL following inhalation of formulations with fine particle doses (FPDs) of 100, 120, and 160 microg of albuterol, respectively. The corresponding peak plasma concentrations of 1.23 +/- 0.29, 1.37 +/- 0.13, and 1.53 +/- 0.11 ng/mL were obtained when asthmatics (six males and six females) were dosed with the same three formulations. The FPD of each formulation correlated well with the area under the curve of plasma concentration-time (AUC(0-8)) profile. Plasma potassium did not show any significant change over a period of 8 h. The forced vital capacity (FVC), the force expiratory volume in 1 s (FEV(1)), and mid expiratory flow (FEF(25-75)) did not correlate with FPD for the three different formulations.

Selective extraction of salbutamol from human plasma with the use of phenylboronic acid

An investigation was conducted on the usage of a single-step extraction procedure involving the retention of a phenylboronate-salbutamol complex on an end-capped C18 solid-phase sorbent to determine the level of salbutamol in human plasma samples. Propranolol, a beta-blocker, was chosen as the internal standard for this assay. In this solid-phase clean-up method, 50 mM sodium carbonate buffer, pH 9.60, was used for conditioning the column as well as washing the endogenous interference. Under the optimal conditions, the recovery of salbutamol from spiked plasma samples was found to be high and reproducible with mean recoveries (n = 3) of more than 90% after elution by using 50% 1 M trifluoroacetic acid in methanol. This sample clean-up step was effectively analyzed under reversed-phase high-performance liquid chromatography with fluorimetric detection. The method was successfully applied to the routine measurement of salbutamol in human plasma from the bioequivalence study on the different administration route of salbutamol. Quantification of salbutamol was convincingly reported with the correlation of coefficient of 0.9980 for the concentration range from 0 to 1000 ng ml(-1). An adequate precision was achieved with both between- and within-day precisions of less than 10% (n = 6) for 100 and 1000 ng ml(-1) and less than 15% (n = 6) for 10 ng ml(-1).

Application of column-switching liquid chromatography-tandem mass spectrometry for the determination of pharmaceutical compounds in tissue samples

Information on plasma-tissue distribution which is important for drug development may be obtained by "in silico" prediction tools. To support the validation of computer models, drug concentrations in rat plasma and tissues (brain, liver, kidney, testes, spleen, gut, lung. heart, muscle, skin and fat) had to be determined. In our work, we established analytical assays for a variety of substances including nicardipine, nitrendipine, felodipine and benzodiazepines. Sample preparation had to be simple and method development as well as analytical run time short to allow a high sample throughput and to minimize resources. Column-switching HPLC after homogenization and protein precipitation served as an efficient, easy and rapid sample preparation method, followed by selective MS-MS detection. Optimization of the trapping procedure was performed in order to reduce the influence of endogenous interferences and to obtain good recovery. Chromatographic separation was necessary to increase the selectivity. The use of small analytical column dimensions (2.1 x 10 mm) was investigated to achieve higher sample throughput without compromising the assay quality. Mass spectrometric parameters, such as ionization modes (positive vs. negative) and ion source types (TurbolonSpray vs. APCI) were screened to find suitable conditions for sensitive analysis of the compounds. Matrix suppression effects were taken into consideration. Calibration samples were prepared in plasma only, whereas quality control samples were prepared in both plasma and tissues to save animals and time. Accuracy and precision were in the range of 84.4-119.1% and 1-16.5%, respectively. Limits of quantification were in the range of 0.5-2.5 ng/ml for plasma and 2-10 ng/ml for tissues. Run times as short as 2.2 min could be achieved.

Novel liquid chromatographic-tandem mass spectrometric methods using silica columns and aqueous-organic mobile phases for quantitative analysis of polar ionic analytes in biological fluids

Use of silica stationary phase and aqueous-organic mobile phases could significantly enhance LC-MS-MS method sensitivity. The LC conditions were compatible with MS detection. Analytes with basic functional groups were eluted with acidic mobile phases and detected by MS in the positive ion mode. Analytes with acid functional groups were eluted with mobile phases at neutral pH and detected by MS in the negative ion mode. Analytes poorly retained on reversed-phase columns showed good retention on silica columns. Compared with reversed-phase LC-MS-MS, 5-8-fold sensitivity increases were observed for basic polar ionic compounds when using silica columns and aqueous-organic mobile phase. Up to a 20-fold sensitivity increase was observed for acidic polar ionic compounds. Silica columns and aqueous-organic mobile phases were used for assaying nicotine, cotinine, and albuterol in biological fluids.

Ultrasensitive determination of NE-100, a novel sigma ligand, in human plasma by liquid chromatography and electrospray ionization tandem mass spectrometry combined with a column-switching technique

For the highly sensitive and selective determination of NE-100, a novel sigma ligand, at levels of low picogram per milliliter of human plasma, a method with excellent reliability employing liquid chromatography (LC)-electrospray ionization (ESI) tandem mass spectrometry (MS-MS) combined with a column-switching technique has been developed. The method involves the use of a stable isotope labeled compound as the internal standard (I.S.), liquid-solid extraction of a plasma specimen with a C8 cartridge, automated on-line clean-up on a short trapping column, subsequent separation on a micro-bore C18 column and detection with ESI-MS-MS using m/z 356 ([M+H]+) as a precursor ion and m/z 105 as a product ion in a selected reaction monitoring mode. The detection and the quantification limits of NE-100 in plasma were 0.5 pg/ml with a signal-to-noise ratio (S/N) of 3 and 2.3 pg/ml, respectively, with an S/N of 21. The good linearity of the calibration graph was obtained in the range of 2.3 to approximately 907.0 pg/ml with excellent reliability. The developed method was applied to the determination of NE-100 in plasma obtained from the clinical trail.

Column switching in high-performance liquid chromatography with tandem mass spectrometric detection for high-throughput preclinical pharmacokinetic studies

A high-throughput liquid chromatography-tandem mass spectrometry method is described for the determination of multiple compounds in dog and rat plasma. After acetonitrile precipitation of plasma proteins, the analytes are pre-concentrated and back-flushed on a reversed-phase column for separation using a switching valve. The analytes are ionized using TurboIon Spray in a positive mode, and detected by multiple reaction monitoring. Automatic tuning software is used for fast method development. The data processing is greatly speeded up by using a powerful quantitation software package. Chromatography of multiple compounds takes only 4 min. The linear calibration curve ranges from 0.5 to 1000 ng/ml. This method was successfully used in the analysis of multi-compounds for preclinical pharmacokinetic studies.