Formulation and evaluation of controlled-release transdermal patches of theophylline-salbutamol sulfate.

Transdermal formulations containing theophylline and salbutamol sulfate (SS) were formulated using hydroxypropylmethylcellulose. Theophylline was loaded by adsorption with the aid of the coadsorbate sodium chloride. The formulations were subjected to in vitro release studies, and the dose of salbutamol and theophylline was optimized to yield the desired flux. The films were uniform and 93 +/- 5.4 microm thick. The in vitro fluxes of theophylline and salbutamol sulfate from the formulation were 1.22 +/- 0.4 mg/h/cm2 and 13.36 +/- 1.02 microg/h/cm2, respectively. The formulation was subjected to pharmacodynamic studies in guinea pigs. The preconvulsive time (PCT) of guinea pigs increased significantly after 4 h, and the same was observed even after 24 h Pharmacokinetic studies were carried out in healthy human volunteers. Theophylline was analyzed in saliva, and salbutamol was analyzed in the blood plasma. The Tmax of the drugs was 3 h, and appreciable concentrations of the drugs above their MEC could be analyzed even after 12 h. The elimination half-life of the drugs was significantly prolonged compared to that for tablets. There were no signs of erythema or edema in the volunteers during observation for a period of 7 days.     

On-line coupling of in vivo microdialysis with tandem mass spectrometry.

The capability of interfacing in vivo microdialysis with mass spectrometry has been demonstrated. The goal of this research was to demonstrate the feasibility of real-time analysis in biological systems using microdialysis in combination with tandem mass spectrometry (MS/MS). Microdialysis sampling was accomplished by surgically implanting a small microdialysis probe into a tissue or area of interest. Molecules diffuse through the membrane of the microdialysis probe due to concentration differences. These molecules are collected in a sample loop and analyzed by tandem mass spectrometry. Sequential injections can be made in as little as 2 min. This capability is advantageous in the study of molecules with very rapid elimination rates. Tris(2-chloroethyl)phosphate (TRCP) was used as a model compound in the development of this analytical technique. As an example of an application of the microdialysis/MS/MS technique, plasma concentration vs time curves were obtained and compared with the plasma concentration profiles obtained using conventional studies. For the microdialysis/MS/MS studies, the average slope from three animals was -0.086 min-1. In comparison, the average slope from four animals from the conventional studies was -0.035 min-1.     

Microdialysis sampling combined with electron spin resonance for superoxide radical detection in microliter samples

Quantitation of superoxide radical (O2.-) production at the site of radical generation remains challenging. Microdialysis sampling is an advantageous tool for sampling from localized environments. It is difficult to combine electron spin resonance (ESR) spin traps with microdialysis because O2.- adducts with common nitrone spin traps have shorter half-lives than typical microdialysis collection times. Furthermore, typical dialysate samples (5-15 microL) suffer significant sensitivity loss when diluted for detection in a conventional ESR flat cell (200 microL). To overcome these difficulties, a cyclic hydroxylamine, 1-hydroxy-4-phosphonooxy-2,2,6,6-tetramethylpiperidine (PP-H), which produces a stable nitroxide radical (PP.) product upon reaction with O2.- was employed. Capillary cells (1.4 microL effective volume) coupled with a loop-gap resonator were utilized to measure PP. in microliter microdialysis samples (LOD 0.36 pmol). A xanthine/xanthine oxidase (X/XO) model system provided sustained O2.- production. When PP-H was included in the X/XO medium external to the microdialysis probe, a relative recovery of 22.1 +/- 1.1 and 57.2 +/- 5.7% for PP. was achieved at perfusion fluid flow rates of 0.5 and 1.0 microL/min, respectively. The respiratory burst in interferon-gamma and zymosan-stimulated RAW 264.7 macrophages was also investigated.     

Pharmacokinetic investigation on a novel antitumour platinum compound in rabbit plasma by inductively coupled plasma mass spectrometry after intravenous administration

The purpose of this study was to investigate a novel platinum anticancer compound named as SM54111 [cis-3, 5-diisopropylsalylic cyclohexanodiaminoplatinum (II)], which is under development as a new drug candidate, on its pharmacokinetics in plasma after intravenous administration to rabbits at concentration of 2.5, 5.0, and 9.0 mg/kg. The concentration of SM54111 in plasma expressed as Pt was determined utilizing ICP-MS method, and the method was thoroughly validated. The data were analyzed with 3P97 pharmacokinetic software to find the parameters. The results showed that the linear range lay at the 1 approximately 1000 ng/mL level, and the LOD and LOQ were 0.4 ng/mL and 1 ng/mL, respectively. It proved that this new drug candidate underwent disposition in rabbit plasma by a two-compartment open model at the three doses above, and the main pharmacokinetic parameters were obtained as the initial concentrations of three doses (C(0)) were 8.68 +/- 0.80, 20.04 +/- 1.92, and 28.88 +/- 2.32 mg/L, respectively; the areas under concentration-time profile from time 0 to 72 h (AUC(0 approximately t)) were 90.0 +/- 13.0, 251.3 +/- 45.3, and 396.9 +/- 61.1 mg*h/L, respectively; the terminal elimination half-life times (t(1/2beta)) 29.1 +/- 4.8, 35.2 +/- 7.5, and 29.4 +/- 2.8 h, respectively; and the total clearances (CL(tot)) were 0.026 +/- 0.004, 0.019 +/- 0.002, and 0.022 +/- 0.004 L/h, respectively. First order rate pharmacokinetics were observed for SM54111 with the doses used, and it showed a long retention and slow elimination in vivo, There showed no prolongation of the t(1/2beta) with larger dose, and the CLs of the three doses were proximate. It is reasonable to surmise that SM54111 follows first order rate pharmacokinetics, and no saturation was detected at concentrations from 2.5 to 9.0 mg/kg. This result suggested that SM54111 experienced an amiable procedure in vivo and was worthy of the further development.     

Formulation and Evaluation of Controlled-Release Transdermal Patches of Theophylline–Salbutamol Sulfate

Transdermal formulations containing theophylline and salbutamol sulfate (SS) were formulated using hydroxypropylmethylcellulose. Theophylline was loaded by adsorption with the aid of the coadsorbate sodium chloride. The formulations were subjected to in vitro release studies, and the dose of salbutamol and theophylline was optimized to yield the desired flux. The films were uniform and 93 ± 5.4 μm thick. The in vitro fluxes of theophylline and salbutamol sulfate from the formulation were 1.22 ± 0.4 mg/h/cm² and 13.36 ± 1.02 μg/h/cm², respectively. The formulation was subjected to pharmacodynamic studies in guinea pigs. The preconvulsive time (PCT) of guinea pigs increased significantly after 4 h, and the same was observed even after 24 h. Pharmacokinetic studies were carried out in healthy human volunteers. Theophylline was analyzed in saliva, and salbutamol was analyzed in the blood plasma. The T_max of the drugs was 3 h, and appreciable concentrations of the drugs above their MEC could be analyzed even after 12 h. The elimination half-life of the drugs was significantly prolonged compared to that for tablets. There were no signs of erythema or edema in the volunteers during observation for a period of 7 days.     

Enhanced microdialysis relative recovery of inflammatory cytokines using antibody-coated microspheres analyzed by flow cytometry

Achieving high relative recovery (RR) of proteins during microdialysis sampling is difficult due to the diffusion limitations inherent to this sampling process. This often causes low microdialysis RR for proteins with molecular weight >10 kDa. A RR enhancement process for microdialysis sampling of proteins has been developed that can be readily used with flow cytometers. Multiplexed RR enhancement and detection of five different cytokines (TNF-alpha, IFN-gamma, IL-2, IL-4, and IL-5) was achieved by including antibody-coated microspheres in the microdialysis perfusion fluid. Inclusion of these antibody-coated microspheres causes an increase in the analyte diffusive driving force across the dialysis membrane and a subsequent increase in the relative recovery. For the five cytokines, typical control and enhanced relative recoveries at a 1.0 microL/min flow rate were as follows (n = 3): TNF-alpha, 5.5 +/- 0.6% and 60.4 +/- 5.8%; IFN-gamma, 2.6 +/- 0.3% and 25.8 +/- 2.3%; IL-5, 1.4 +/- 0.2% and 4.9 +/- 0.1%; IL-4, 10.9 +/- 0.6% and 78.8 +/- 8.0%; and IL-2, 4.1 +/- 0.4% and 19.8 +/- 2.5%. Using this approach, a four- to 12-fold enhancement of microdialysis RR was achieved for the five cytokines from a quiescent solution. The enhancement varies among the five cytokines and may be due to different diffusive and antibody binding properties. TNF-alpha exhibited the highest RR enhancement, while IL-5 exhibited the lowest. Experimental parameters that affect the enhancement, such as flow rate, sample collection volume, and bead density, were studied.     

Microdialysis sampling membrane performance during in vitro macromolecule collection

Microdialysis sampling is well-established for sampling small molecules. Recently, there has been an increased interest toward collecting macromolecules using microdialysis sampling. In this work, fluorescein isothiocyanate-labeled dextrans (FITC-dextrans) with molecular weight between 10 and 70 kDa were chosen as representative molecules to study analyte mass transport properties during microdialysis sampling using different lengths (2 and 10 mm) of 100-kDa MWCO polyethersulfone membranes. Experiments were performed in both well-stirred and quiescent phosphate-buffered saline solutions as well as in a 0.3% agar solution. Different fundamental parameters affecting microdialysis sampling of macromolecules, including effective membrane diffusion coefficients, were evaluated. The applicability of the most-often-cited Bungay et al. mass transfer model was compared to experimental data for the FITC-dextrans. For the larger macromolecules, the membrane provides a significant mass transport resistance most likely caused by hindered diffusion. These experimental aspects that are critical to microdialysis sampling of macromolecules are presented.     

Continuous on-line monitoring of extracellular ascorbate depletion in the rat striatum induced by global ischemia with carbon nanotube-modified glassy carbon electrode integrated into a thin-layer radial flow cell

This study describes a novel analytical system integrating in vivo microdialysis sampling with a radial thin-layer flow cell with a single-walled carbon nanotube (SWNT)-modified glassy carbon electrode as working electrode for continuous and on-line monitoring of ascorbate depletion in the rat striatum induced by global ischemia. The SWNTs, especially those after vacuum heat treatment at 500 degrees C, are found to be able to enhance the electron-transfer kinetics of ascorbate oxidation at a low potential (ca. -50 mV) and possess a strong ability against electrode fouling. These properties essentially make it possible to determine ascorbate with a good stability and high selectivity against catecholamines and their metabolites and other electroactive species of physiological levels. While being integrated with in vivo microdialysis to assemble an on-line analytical system, the electrode is proved useful for continuous and sensitive monitoring of the basal dialysate level of ascorbate and its depletion in the rat striatum induced by global ischemia. The basal dialysate level of ascorbate is determined to be 5.0 +/- 0.5 microM (n = 5) and a 50 +/- 10% (n = 3) depletion is recorded for the basal ascorbate after 4 h of global ischemia.     

Effect of dexamethasone on gliosis, ischemia, and dopamine extraction during microdialysis sampling in brain tissue

Microdialysis sampling of the brain is an analytical technique with numerous applications in neuroscience and the neurointensive care of brain-injured human patients. Even so, implanting microdialysis probes into brain tissue causes a penetration injury that triggers gliosis (the activation and proliferation of glial cells) and ischemia (the interruption of blood flow). Thus, the probe samples injured tissue. Mitigating the effects of the penetration injury might refine the technique. The synthetic glucocorticoid dexamethasone is a potent anti-inflammatory and immunosuppressant substance. We performed microdialysis in the rat brain for 5 days, with and without dexamethasone in the perfusion fluid (10 μM for the first 24 h and 2 μM thereafter). On the first and fourth day of the perfusion, we performed dopamine no-net-flux measurements. On the fifth day, we sectioned and stained the brain tissue and examined it by fluorescence microscopy. Although dexamethasone profoundly inhibited gliosis and ischemia around the probe tracks it had only modest effects on dopamine no-net-flux results. These findings show that dexamethasone is highly effective at suppressing gliosis and ischemia but is limited in its neuroprotective activity.     

In situ and multisubstrate detection of elastase enzymatic activity external to microdialysis sampling probes using LC-ESI-MS

Extracellular proteases play significant roles in mammalian development and disease. Enzymatic activity external to a microdialysis sampling probe can be determined by infusing judicious choices of substrates followed by collecting and measuring the products. Porcine pancreatic elastase was used as a model enzyme with two substrates possessing different cleavage sites, N-methoxysuccinyl-Ala-Ala-Pro-Val-7-amino-4-methylcoumarin (FL-substrate) and N-succinyl-Ala-Ala-Ala-p-nitroanilide (UV-substrate). These substrates were infused through the microdialysis sampling probe to a solution containing elastase. The resulting four products and the remaining two substrates were collected into the dialysate and were subsequently analyzed off-line using liquid chromatography-mass spectrometry (LC-MS) with electrospray ionization (ESI). All analytes were identified using extracted ion chromatograms of m/z 628 (FL-substrate), m/z 452 (UV-substrate), m/z 471 (N-methoxysuccinyl-Ala-Ala-Pro-Val, FL-NTP), m/z 332 (N-succinyl-Ala-Ala-Ala, UV-NTP), m/z 176 (7-amino-4-methylcoumarin, AMC), and m/z 139 (p-nitroaniline, pNA). FL-NTP and FL-substrate exhibited 10-fold higher ion production as compared to AMC with equimolar standards. Microdialysis sampling combined with LC-ESI-MS detection allowed for in situ determination of the enzymatic activity of a protease external to the microdialysis probe when using different peptide-based substrates.     

Improved temporal resolution for in vivo microdialysis by using segmented flow

Microdialysis sampling probes were interfaced to a segmented flow system to improve temporal resolution for monitoring concentration dynamics. Aqueous dialysate was segmented into nanoliter plugs by pumping sample stream into the base of a tee channel structure microfabricated on a PDMS chip that had an immiscible carrier phase (perfluorodecalin) pumped into the cross arm of the tee. Varying the oil flow rate from 0.22 to 6.3 microL/min and sample flow rate from 42 to 328 nL/min allowed control of plug volume, interval between plugs, and frequency of plug generation between 6 and 28 nL, 0.6 and 10 s, and 0.1 and 1.7 Hz, respectively. Temporal resolution of the system, determined by measuring fluorescence in individual sample plugs following step changes of fluorescein concentration at the sampling probe surface, was as good as 15 s. Temporal resolution was independent of both sampling flow rate and distance that samples were pumped from the sampling probe. This effect is due to the prevention of Taylor dispersion of the sample as it was transported by segmented flow. In contrast, without flow segmentation, temporal resolution was worsened from 25 to 160 s as the detection point was moved from the sampling probe to 40 cm downstream. Glucose was detected by modifying the chip to allow enzyme assay reagents to be mixed with dialysate as sample plugs formed. The resulting assay had a detection limit of 50 microM and a linear range of 0.2-2 mM. This system was used to measure glucose in the brain of anesthetized rats. Basal concentration was 1.5 +/- 0.1 mM (n = 3) and was decreased 60% by infusion of high-K(+) solution through the probe. These results demonstrate the potential of microdialysis with segmented flow to be used for in vivo monitoring experiments with high temporal resolution.     

In vivo microdialysis and thermospray tandem mass spectrometry of the dopamine uptake blocker 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)-piper azine (GBR-12909)

Microdialysis in conjunction with thermospray tandem mass spectrometry was employed in following the time course of the experimental drug GBR-12909 in vivo. GBR-12909 is 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-3(phenylpropyl)-piperazine. An important feature of microdialysis exploited in the method is the elimination of sample cleanup procedures. The detection limit was determined to be 100 pg and the relative standard deviation of estimates for standard solution in the range of 50 nmol/L to 1 mumol/L concentrations was found to be 17%. Important factors in obtaining high sensitivity and reproducibility were carrier phase composition and operation in the flow injection mode. The maximum concentration of GBR-12909 in the brain for a dose of 100 mg/kg i.p. was determined to be 250 nmol/L with the maximal concentration occurring approximately 2 h postinjection. This represents a 40-fold lower concentration of GBR-12909 in the brain as compared to cocaine concentration obtained at a dose of 30 mg/kg, which was estimated earlier under similar experimental conditions. This observation could explain the discrepancy between relative in vivo and in vitro potencies of the two drugs.     

Ultrasensitive determination of phencyclidine in body fluids by surface ionization organic mass spectrometry

Gas chromatography (GC)/surface ionization organic mass spectrometry (SIOMS) has been found to give much higher sensitivity for measurements of phencyclidine (PCP) than the conventional GC/electron impact (EI)-mass spectrometry (MS). Thus, we have established a detailed procedure for measurements of PCP in body fluids by both mass chromatography and selected-ion monitoring (SIM) of SIOMS using pethidine as an internal standard (IS). Good linearity was found in the range of 0.25-10 ng/mL of whole blood or urine, when measured by mass chromatography, and in the range of 0.025-1.0 ng/mL of whole blood by SIM. The recoveries of PCP and IS spiked to whole blood were 106 +/- 17% at 1 ng/mL and 113 +/- 11% at 5 ng/mL; that of IS was 97.8 +/- 10.4% at 5 ng/mL. The detection limits (signal-to-noise ratio = 3) were estimated to be 0.05 ng/mL of whole blood or urine by mass chromatography and 0.01 ng/mL of whole blood by SIM. The coefficients of intraday and interday variations were not greater than 10.3%. We could detect PCP from rat whole blood 2 h after subcutaneous injection of PCP (1 mg/kg) by mass chromatography. The mean PCP concentration in rat blood was 47.7 +/- 6.2 ng/mL (mean +/- SD, n = 4).     

On-line coupling of microdialysis sampling with microchip-based capillary electrophoresis

Microdialysis sampling is a technique that has been used for in vivo and in vitro monitoring of compounds of pharmaceutical, biomedical, and environmental interest. The coupling of a commercially available microdialysis probe to a microchip-based capillary electrophoresis (CE) system is described. A continuously flowing dialysate stream from a microdialysis probe was introduced into the microchip, and discrete injections were achieved using a valveless gating approach. The effect of the applied voltage and microdialysis flow rate on device performance was investigated. It was found that the peak area varied linearly with the applied voltage. Higher voltages led to lower peak response but faster separations. Perfusion flow rates of 0.8 and 1.0 microL/min were found to provide optimal performance. The on-line microdialysis/microchip CE system was used to monitor the hydrolysis of fluorescein mono-beta-d-galactopyranoside (FMG) by beta-d-galactosidase. A decrease of the FMG substrate with an increase in the fluorescein product was observed. The temporal resolution of the device, which is dependent on the CE separation time, was 30 s. To the best of our knowledge, this is the first reported coupling of a microdialysis sampling probe to a microchip capillary electrophoresis device.     

Microdialysis sampling extraction efficiency of 2-deoxyglucose: role of macrophages in vitro and in vivo

Macrophages are a class of inflammatory cells believed to direct the outcome of device biocompatibility. Despite their relevance to implanted in vivo devices, particularly implanted glucose sensors, few studies have attempted to elucidate how these cells affect device performance. Microdialysis sampling probes were used to determine glucose uptake alterations in the presence of resting and activated macrophages in vitro. Significant differences for 2-deoxyglucose (2-DG) relative recovery at 1.0 microL/min were observed between resting (74 +/- 7%, n = 18) and lipopolysaccharide (LPS) (1 microg/mL)-activated (56 +/- 6%, n = 18) macrophages in culture that had 2-DG spiked into the media (p < 0.005). To establish if in vitro characterization could be correlated to in vivo studies, microdialysis probes were implanted into the dorsal subcutis of male Sprague-Dawley rats for 0, 3, 5, and 7 days. An internal standard, 2-DG, was passed through the microdialysis probe during in vivo studies. No significant differences in 2-DG extraction efficiency from the probe into the tissue site were observed in vivo among microdialysis probes implanted into the subcutaneous space of Sprague-Dawley rats for either 3, 5, or 7 days vs probes implanted the day of sample collection. These results suggest that macrophage activation in vivo at implant sites is much lower than highly activated macrophages in vitro. It is important to note that these results do not rule out the potential for increased glucose metabolism at sensor implant sites.     

Combining microdialysis, NanoLC-MS, and MALDI-TOF/TOF to detect neuropeptides secreted in the crab, Cancer borealis

Microdialysis is a useful technique for sampling neuropeptides in vivo, and decapod crustaceans are important model organisms for studying how these peptides regulate physiological processes. However, to date, no microdialysis procedure has been reported for sampling neuropeptides from crustaceans. Here we report the first application of microdialysis to sample neuropeptides from the hemolymph of the crab, Cancer borealis. Microdialysis probes were implanted into the pericardial region of live crabs, and the resulting dialysates were desalted, concentrated, and analyzed by LC-ESI-QTOF and MALDI-TOF/TOF mass spectrometry. Analysis of in vitro microdialysates of hemolymph revealed more neuropeptides and fewer protein fragments than hemolymph prepared by typical analysis methods. Mass spectra of in vivo dialysates displayed neuropeptides from 10 peptide families, including the RFamide, allatostatin, and orcokinin families. In addition, GAHKNYLRFa, SDRNFLRFa, and TNRNFLRFa were sequenced from hemolymph dialysates. The detection of these neuropeptides in the hemolymph suggests that they are functioning as hormones as well as neuromodulators. In vivo microdialysis offers the capability to further study these and other neuropeptides in crustacean hemolymph, complementing current tissue-based studies and extending our knowledge of hormonal regulation of physiological states.     

Topical bioequivalence of acyclovir creams using dermal microdialysis in pigs: a new model to evaluate bioequivalence for topical formulations

The aim was to evaluate the bioequivalence of topically applied Acyclovir (ACV) creams using dermal microdialysis (DMD) in a pig model. Three ACV creams (3%), ACV1, ACV2 and ACV3, were topically administrated on the dorsum of pigs, and the DMD sampling technique was used to continuously collect microdialysate. The concentration of ACV in microdialysate was measured by HPLC and the concentration-time profiles were used to calculate pharmacokinetic parameters. The results showed that 90% confidence interval (CI) of the ratio of AUC(0-4 h) of ACV2 and ACV3 was between 88.2 and 105.7%, which was within the acceptance range (80-125%). Ninety percent CI of the ratio of C(max) of ACV2 and ACV3 was between 87.4 and 124.4%, which was within the acceptance range (80-125%). These data indicate that ACV2 and ACV3 used in this study were bioequivalent. This study demonstrates that the pig model coupled with DMD sampling can potentially provide a cost-effective strategy to evaluate topical drug delivery and its associated pharmacokinetic studies.     

Interleukin-6 collection through long-term implanted microdialysis sampling probes in rat subcutaneous space

Microdialysis sampling is a method that has promise for collection of important signaling proteins such as cytokines that are involved in every aspect of the immune response. The objective of this study was to determine the role of membrane and tissue alterations on the reduction of interleukin-6 (IL-6) relative recovery of microdialysis probes implanted for 3 and 7 days versus probes implanted on day 0 (acute implant or control probe). Lipopolysaccharide (LPS), a bacterial endotoxin, was used to elicit IL-6 production in the animals. Within the same animal, the recovery of IL-6 through control probes implanted the day of sample collection was compared to the 3- or 7-day implanted probes. Two hours post-LPS administration, the IL-6 concentrations obtained from either the 3-day or 7-day implanted probe were reduced by more than 8-fold when compared to the control probe. The IL-6 concentrations obtained for the 3-day versus control probes 2-h post-LPS injection were 730 +/- 310 and 6440 +/- 1550 pg/mL (mean +/- SD, n = 3), respectively. For the 7-day implant, the IL-6 concentration in the dialysis probe obtained at 2-h post-LPS injection was 990 +/- 590 versus 5520 +/- 1430 pg/mL (mean +/- SD, n = 3) for the control. In vitro recovery experiments and scanning electron microscopy images combined with the in vivo data suggest that the decreased IL-6 content in the dialysate was caused principally by tissue alterations or tissue encapsulation rather than membrane blockage with biological components (membrane biofouling).     

Formulation and pharmacokinetics evaluation of puerarin nanocrystals for intravenous delivery

Puerarin is a very widely used drug for treating coronary heart disease. Owing to its poor water solubility and the adverse drug reactions caused by cosolvents having been confirmed by SFDA, the aim of present study was to construction and evaluation the puerarin nanocrystals in vitro and in vivo. The nanocrystals prepared were characterized using PCS, AFM, TEM, SEM and DSC. For the assessment of the pharmacokinetic parameters the developed formulations have been intravenous administered to beagle dogs. Results revealed that a narrow size distributed nanocrystals composed of crystallized spherical particles with a mean particle size of 423.6 +/- 17.3 nm, a poly-dispersity index of 0.13 +/- 0.07 and a negative charges around -30 mV was obtained. Puerarin dissolution velocity and saturation solubility were enhanced by the nanocrystals. DSC analysis revealed that the crystallinity of the puerarin was preserved during the high pressure homogenization and freeze-drying processes. Administration of the nanocrystals led to a mean plasma profile with almost similarly low variations in comparison to the reference solution, however with no initial blood peak as observed with the solution formulation. The puerarin nanocrystals exhibited a significantly (P < 0.05) reduced Cmax and clearance, and a significantly (P < 0.05) greater MRT, clearance and elimination half-life compared to the puerarin solution. These results revealed the opportunity to formulate puerarin in nanocrystals for intravenous delivery with higher safety.     

Electrospray ionization mass spectrometry coupled to reversed-phase ion-pair high-performance liquid chromatography for quantitation of sodium borocaptate and application to pharmacokinetic analysis

We have developed a quantitative assay using electrospray ionization mass spectrometry coupled to reversed-phase ion-pair liquid chromatography (LC/MS) for quantitation of sodium borocaptate (BSH) in human plasma. The assay was developed using a Micromass Q-TOF II mass spectrometer equipped with an orthogonal electrospray source. The mobile phase was a 1:1 solution of methanol and 5 mM aqueous tetrabutylammonium acetate flowing at 0.2 mL/min, and the chromatography was performed using a Machery-Nagel Nucleosil C18 column. Plasma samples from patients who had received an intravenous infusion of sodium borocaptate (Na2B12H11SH), frequently referred to as BSH, were prepared for analysis by precipitation with acetonitrile. Following this, the supernatants were collected, and 40 microL was injected onto the column for analysis. The LC/MS assay was linear over a BSH plasma concentration range of 20-0.5 microg/mL with acceptable variability for both intra- and interassay precision. The LC/MS assay was used to generate pilot pharmacokinetic data for the plasma disposition of BSH in humans. The disposition of BSH was found to be consistent with a two-compartment model with first-order elimination from the central compartment. The mean total body plasma clearance was 95.7 +/- 30.8 m/min and the harmonic mean terminal half-life was 3.6 h.