Quantification of clofarabine in urine and plasma by LC-MS/MS: suitable for PK study and TDM in pediatric patients with relapsed or refractory ALL.

Clofarabine is approved for the treatment of relapsed or refractory acute lymphoblastic leukemia (ALL) in pediatric patients aged 1 to 21 years. Its pharmacokinetic (PK) exposure is strongly related to clinical outcomes and high risk of adverse reactions. PK-guided dosing of nucleoside analogs has the potential to improve survival and reduce toxicity in children. Considering that blood collection is an invasive operation and that the volume of blood collected is usually limited in pediatric ALL patients, a convenient and efficient method for the quantification of clofarabine in human urine and plasma was established with an LC-MS/MS system. Standard curves were shown to be liner in the range of 2.00-1000.00 ng mL-1 in both urine and plasma. Analytical validation of the assay included the assessment of linearity, accuracy (RE: -6.62% to 2.32%), intra-assay precision (RSD: 0.81% to 3.87%) and inter-assay precision (RSD: 1.88% to 5.69%). The absolute recovery rates of clofarabine were 85.50 ± 4.80%, 89.40 ± 0.70% and 98.00 ± 0.40% in urine and were 80.76 ± 1.88%, 86.81 ± 0.75%, 88.10 ± 0.61% in plasma at 5.00, 30.00 and 800.00 ng mL-1, respectively. The selectivity, stability and matrix effects conformed to the biological sample analysis requirements. The cumulative urine excretion rates for 24 hours of the three children with relapsed and refractory acute lymphoblastic leukemia were 72.22%, 87.88%, 82.16%, respectively. The PK data of the pediatric patient numbered lflb13-05 are very inconsistent with that of the other two children subjects, demonstrating that there may be an individual variation in Chinese pediatric patients, so the dose should be individualized based on the monitoring of drug concentration. The method is convenient, sensitive, and accurate, and it is suitable for the determination of clofarabine urine and plasma concentration. This is the first report on the pharmacokinetics of clofarabine in Chinese ALL children. Furthermore, it could be an alternative method to clinical monitoring of clofarabine.

Automated On-Line Microdialysis Sampling Coupled with HPLC for Synchronous Determination of Puerarin in Subcutaneous Tissue and Plasma Following Topical Administration.

BACKGROUND: Studies on transdermal administration have shown that puerarin can permeate rat skin rapidly with long-term drug delivery, but there are no reports demonstrating whether topical use of puerarin can provide a steady plasma concentration to produce therapeutic effects. The aim of the study is to evaluate the percutaneous penetration and plasma concentration of puerarin after transdermal administration in experimental rats. METHODS: The skin and plasma concentration of puerarin was quantified by microdialysis, and the recovery was determined by retrodialysis. Puerarin microdialysate concentrations were measured by on-line high-performance liquid chromatography (HPLC). Puerarin release from gels was determined by analysis of the amount of remaining drug after dermal application to hairless skin. RESULTS: The average recoveries of puerarin in the skin and plasma over an 8-hour period were 31.49% and 15.5%. Puerarin was rapidly absorbed with transdermal administration, with the C(max) values of 30.64 µg/mL and 3.53 µg/mL, the AUC0 t-values of 11.60 and 1.48 µg/mL per minute, for skin and plasma, respectively. CONCLUSIONS: The results indicate that the automated on-line microdialysis technique can be used to detect the skin and plasma pharmacokinetics of puerarin and that the use of skin gel can provide an effective means of puerarin administration.

Liquid chromatography-electrospray quadrupole linear ion trap mass spectrometry method for the quantitation of palonosetron in human plasma and urine: Application to a pharmacokinetic study.

The new analytical method for the determination of palonosetron in human plasma and urine has been developed based on liquid chromatography-mass spectrometry. The method utilized tramadol as the internal standard (IS). Separation was carried out on a Zorbax Eclipse TC-C(18) column using methanol-1mM ammonium formate in water (containing 0.1% formic acid, v/v, pH=2.8) as mobile phase for gradient elution. Detection is carried out by multiple reaction monitoring (MRM) on 3200 Qtrap mass spectrometry. The method has a chromatographic run time of 5.5 min and is linear within the concentration range 0.01-5.00 ng/mL for plasma and 0.10-30.00 ng/mL for urine both with a LOD of 0.003 ng/mL. Intra- and inter-day RSD of the concentration was 3.66-6.60%, 1.29-7.71% for plasma and 2.39-5.76%, 2.06-7.13% for urine. The relative error (RE) was -4.58% to 3.26% for plasma and -1.47% to 2.53% for urine. The recovery rates of palonosetron and IS both for plasma and urine were more than 90%. Palonosetron was stable under all the conditions tested. The method was successfully used to analyze palonosetron in human plasma and urine over a period of 168 h after intravenously pumping a single dose of 0.25mg to volunteers. No significant differences were found between the pharmacokinetic parameters and urine accumulated excretory rate for male and female volunteers (P>0.05). A two-compartment model was obtained after administrations. Palonosetron was eliminated at a slow rate in volunteers. The mean urine accumulated excretory rate was 25.97 ± 12.87%. Inter-individual differences could not be neglected due to the high coefficient of variety in several pharmacokinetic parameters and the urine accumulated excretion.

The mutant selection window in rabbits infected with Staphylococcus aureus.

BACKGROUND: The mutant selection window hypothesis, originally based on agar plate assays, may lead to new antimicrobial dosing strategies that severely restrict the acquisition of resistance. However, it has not been directly tested in an animal model of infection. METHODS: Local infection with Staphylococcus aureus was established in rabbits, and the infected animals were treated orally with various doses of levofloxacin. Changes in levofloxacin concentration, levofloxacin susceptibility, and counts of total and resistant viable bacteria were monitored at the site of infection. RESULTS: S. aureus lost levofloxacin susceptibility when drug concentrations at the site of infection fluctuated between the lower and upper boundaries of the window, defined in vitro as the minimum inhibitory concentration (MIC)(99) and the mutant prevention concentration (MPC), respectively. The upper boundary of the selection window in vivo was estimated as an AUC(24)/MPC value of ~25 h, where AUC(24) is the area under the drug concentration time curve in a 24-h interval. The lower boundary was estimated as an AUC(24)/MIC value of ~20 h. CONCLUSIONS: The mutant selection window exists in vivo, and its boundaries fit well with those determined in vitro. Maintenance of antimicrobial concentrations above the window is expected to suppress the outgrowth of resistant mutant subpopulations.

In vitro activity of cefepime combined with sulbactam against clinical isolates of carbapenem-resistant Acinetobacter spp.

The aim of this study was to assess the in vitro activity of cefepime combined with sulbactam against carbapenem-resistant clinical isolates of Acinetobacter spp. The checkerboard method was used to determine whether combinations act synergistically against these strains. Twenty-three Acinetobacter baumannii and one Acinetobacter junii found to be carbapenem resistant were included in the study. The susceptibility results for cefepime and sulbactam were interpreted according to the guidelines of the Clinical and Laboratory Standards Institute. Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922 were used as quality control strains. The combination of cefepime and sulbactam demonstrated the following interactions: 33.3% (8/24) synergism; 58.3% (14/24) partial synergism; 4.2% (1/24) additive; 4.2% (1/24) indifference; and no antagonism (minimum and maximum fractional inhibitory concentration index 0.25 and 1.5, respectively). According to our in vitro study results, combinations of cefepime with sulbactam have moderate synergistic activity against some carbapenem-resistant strains of Acinetobacter spp., which could be beneficial for the treatment of infections due to multidrug-resistant strains of Acinetobacter spp.