Analysis of Busulfan in Plasma by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

Bone marrow transplantation is used to treat particular types of cancers such as lymphoma, leukemia, and multiple myeloma. Appropriate dosing of busulfan during the preparative phase is critical for a successful allograft; if blood concentrations get too high significant liver toxicity can occur, if blood concentrations are too low, then graft-versus-host disease (GVHD) can develop. Busulfan monitoring in blood allows hospitals with the opportunity to provide individualized medicine to patients and improve overall patient outcome. Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) is an important analytical method for quantification of busulfan in plasma in order to optimize the dose. © 2020 Wiley Periodicals LLC. Basic Protocol: Analysis of busulfan by liquid chromatography/mass spectrometry.

Analysis of Immunosuppressant Drugs in Whole Blood by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

Immunosuppressant medications help suppress the immune system response through inhibition of various checkpoints in the regulatory biochemical pathway. This is useful in prevention of organ rejection in transplantation or in the treatment of autoimmune diseases such as lupus or rheumatoid arthritis. Quantification of immunosuppressive drugs in blood is needed clinically for optimization of treatment and to avoid toxicity or unwanted side effects. Here, we describe a quantitative method to determine the concentration of cyclosprine A, tacrolimus, sirolimus, and everolimus in whole blood. This method has been used for many years clinically to support patient care. © 2020 by John Wiley & Sons, Inc.

Automated analysis of dried urine spot (DUS) samples for toxicology screening.

BACKGROUND: Dried specimens have been proposed in multiple environments to minimize costs associated with specimen storage and shipping in clinical studies. This report describes the development and validation of an automated method for qualitative toxicology screening of dried urine samples using LC-MS/MS. METHODS: Urine standards containing 41 compounds were prepared and applied to filter paper cards. Dried urine was eluted from the cards using a Dried Blood Spot (DBS) autosampler from Spark Holland, which was plumbed inline with a Thermo Scientific Turboflow chromatography system for subsequent MS/MS detection with selected reaction monitoring. Limits of detection, precision of peak areas, repeatability, and carryover studies were conducted. Concordance with a reference LC-MS/MS method using liquid samples was evaluated using remnant discarded specimens. RESULTS: The limit of detection ranged from 5 to 75 ng/mL for most compounds. At the LOD for each analyte, the peak area precision ranged from 8 to 29%. For 20 repeat injections of samples spiked at ±25% of the LOD, there was a 4% false positive rate for the 75% × LOD samples, and a 0.4% false negative rate for the +125% × LOD samples. In comparing 40 known positive specimens analyzed with the DUS method and a liquid urine reference method, there was 88% agreement. Analysis of 10 known negative specimens yielded negative results. There was no significant carryover detected up to 2000 ng/mL for any of the analytes in the assay. CONCLUSION: Using a robotic DUS sampling an inline HTLC-MS/MS system, we have developed and validated a fully-automated and robust method for multi-analyte detection of drugs of abuse in dried urine specimens.

Quantification of Tricyclic Antidepressants in Serum Using Liquid Chromatography Electrospray Tandem Mass Spectrometry (HPLC-ESI-MS/MS).

Tricyclic antidepressants (TCA) are used to treat major depressive disorder and other psychological conditions. The efficacy of these drugs is tied to a narrow therapeutic window. Inappropriately high drug concentrations can result in serious side effects such as hypotension, tachycardia, or coma. As a result, concentrations of tricyclic antidepressants are routinely monitored to ensure compliance and to prevent adverse side effects by dose adjustments. We describe a method for the determination of concentrations of amitriptyline, desipramine, imipramine, and nortriptyline in human serum using high-performance liquid chromatography coupled to a tandem mass spectrometer with electrospray ionization (HPLC-ESI-MS/MS). The method is rapid, requiring only 3.5 min per analysis. The method requires 100 µL of serum. Concentrations of each TCA were quantified by a calibration curve relating the peak area ratio of each TCA analyte to a deuterated internal standard (amitriptyline-D3, desipramine-D3, imipramine-D3, and nortriptyline-D3). The method was linear from ~70 ng/mL to ~1000 ng/mL for all TCAs, with imprecision ≤ 12%.

Development and validation of a clinical HPLC method for the quantification of hydroxychloroquine and its metabolites in whole blood.

BACKGROUND: Therapeutic drug monitoring for hydroxychloroquine (HCQ) has been suggested to assess nonadherence and optimize treatment efficacy in systemic lupus erythematosus patients. MATERIALS & METHODS: After protein precipitation, HCQ and its metabolites, desethylhydroxychloroquine and desethylchloroquine were separated on a phenyl column and monitored by fluorescence detection. The method was linear from 50 to 4000 ng/ml for HCQ. The intra-day and inter-day precision of HCQ, desethylhydroxychloroquine and desethylchloroquine ranged from 4.3 to 10.3%. LLOQ was 50 ng/ml for HCQ. CONCLUSION: The method is very practical and was applied to routinely monitor the steady state whole blood exposure of HCQ and its metabolites in systemic lupus erythematosus patients. It well correlated with our LC-MS/MS and another HPLC method.

A rapid and reliable method for the quantitation of hydroxychloroquine in serum using turbulent flow liquid chromatography-tandem mass spectrometry.

BACKGROUND: Hydroxychloroquine is routinely used in managing systemic lupus erythematosus and rheumatoid arthritis. Whole blood levels are currently measured in the laboratory but at least one study suggests that serum levels may be equally useful. Moreover, serum samples are the preferred matrix type in the clinical laboratory as a result of their reduced complexity compared to whole blood. These observations suggest that the clinical utility of serum hydroxychloroquine levels needs to be reevaluated using larger studies and more robust assays. We report a turbulent flow LC-MS/MS method we developed for this purpose. METHODS: After protein precipitation from serum with 0.33 mol/l perchloric acid, hydroxychloroquine and its deuterated analog were injected onto a Cyclone turbulent flow column for sample cleanup. Analytical separation was accomplished on a HypersilGold C8 column with a gradient of water and methanol, each containing 0.1% formic acid and 10 mmol/l ammonium formate. Analytes were ionized and detected by electrospray ionization mass spectrometry with multiple reaction monitoring. RESULTS: Our method was linear from 15.7 to 2000 ng/ml. Total imprecision at multiple levels was <5% and accuracy was within ±15%. The method showed minimal carryover. Our extraction efficiency was 103% and the matrix factor was 101%. Comparison with a reference laboratory method identified constant bias but good correlation between the 2 methods. CONCLUSIONS: We present a novel turbulent flow liquid chromatography-tandem mass spectrometry method for quantification of hydroxychloroquine in serum. Our method has comparable sensitivity, selectivity, precision, accuracy, and linearity to previously reported methods. However, it offers simpler sample processing, shorter overall analysis time, and minimal carryover. These characteristics make our method well-suited for efficient analysis of the large number of samples necessary for studies on the clinical utility of serum HQ levels.

Rapid quantification of the aminoglycoside arbekacin in serum using high performance liquid chromatography-tandem mass spectrometry.

BACKGROUND: This project entails the development and validation of a method for quantification of the aminoglycoside antibiotic arbekacin in serum using liquid chromatography tandem mass spectrometry (LC-MS/MS) for therapeutic drug monitoring in future clinical trials. METHODS: Following a protein precipitation with 0.3 mol/l perchloric acid containing internal standard dibekacin at a concentration of 0.6 µg/ml, human serum samples containing arbekacin were analyzed using a Hypersil Gold PFP column and a liquid chromatography system. Elution occurred with a gradient of water and acetonitrile, each containing 0.05% (v/v) trifluoroacetic acid and 0.1% (v/v) formic acid. Analytes were detected over a 3.25 minute run time using a tandem mass spectrometer with a heated electrospray-ionization (HESI) source in positive ionization mode with selected reaction monitoring (SRM). Matrix effects, carryover, linearity, recovery, precision, and limit of quantification were carefully evaluated. RESULTS: The limit of quantification for arbekacin was 0.1 µg/ml. All simple and total precision CV's were less than 6.2%. The method was linear from 0.1 µg/ml to 45.9 µg/ml (slope of 0.973). The mean recovery ranged from 94.7 to 103.8%. No matrix effects were detected. CONCLUSIONS: This developed and validated LC-MS/MS method allows for the quantification of arbekacin in serum following protein precipitation.

The development and clinical validation of a turbulent-flow liquid chromatography-tandem mass spectrometric method for the rapid quantitation of docetaxel in serum.

BACKGROUND: Docetaxel is a second generation taxane utilized as an anti-neoplastic agent in cancer chemotherapies. Traditional treatment regimens have resulted in significant adverse effects, resulting in the shift to more frequent drug administration at lower doses. As a result, it is important to monitor serum docetaxel concentrations to optimize efficacy and minimize adverse effects. METHODS: Serum containing docetaxel was combined with acetonitrile containing deuterated internal standard, and following protein precipitation, supernatant was diluted with water for on-line sample extraction. Following turbulent-flow chromatography (TFC), analytic separation was achieved on a Hypersil Gold C-18 (50×2.1mm) column and the eluent analyzed using a TSQ Vantage mass spectrometer with selected reaction monitoring. Matrix effects were characterized in addition to carryover, precision, linearity, recovery and functional sensitivity. RESULTS: The simple and complex precision for the assay at multiple concentrations was ≤6.2%. The assay has functional sensitivity of <3ng/ml, and is linear from 8.1 to 1978ng/ml. Method comparison studies with a reference HPLC-MS/MS method show a slope of 0.84 with a Spearman coefficient of 0.99. CONCLUSIONS: Based on the validation metrics, we have generated a sensitive and automated TFC-MS/MS method for docetaxel quantitation in serum.

Prolonged control of replication-competent dual- tropic human immunodeficiency virus-1 following cessation of highly active antiretroviral therapy.

BACKGROUND: While initiation of highly active antiretroviral therapy (HAART) during primary HIV-1 infection occasionally results in transient control of viral replication after treatment interruption, the vast majority of patients eventually experience a rebound in plasma viremia. RESULTS: Here we report a case of a patient who was started on HAART during symptomatic primary infection and who has subsequently maintained viral loads of < 50 copies/mL for more than nine years after the cessation of treatment. This patient had a high baseline viral load and has maintained a relatively high frequency of latently infected CD4(+) T cells. In addition, he does not have any known protective HLA alleles. Thus it is unlikely that he was destined to become a natural elite controller or suppressor. The mechanism of control of viral replication is unclear; he is infected with a CCR5/CXCR4 dual-tropic virus that is fully replication-competent in vitro. In addition, his spouse, who transmitted the virus to him, developed AIDS. The patient's CD4(+) T cells are fully susceptible to HIV-1 infection, and he has low titers of neutralizing antibodies to heterologous and autologous HIV-1 isolates. Furthermore, his CD8(+) T cells do not have potent HIV suppressive activity. CONCLUSION: This report suggests that some patients may be capable of controlling pathogenic HIV-1 isolates for extended periods of time after the cessation of HAART through a mechanism that is distinct from the potent cytotoxic T lymphocyte (CTL) mediated suppression that has been reported in many elite suppressors.

Blood concentrations of chlorhexidine in hospitalized children undergoing daily chlorhexidine bathing.

We collected serial blood samples from children in the intensive care unit who underwent daily bathing with 2% chlorhexidine gluconate (CHG)-impregnated cloths. Low concentrations of CHG were detected in a few blood samples, indicating absorption through intact skin. There was no suggestion that CHG accumulated in the blood with repeated exposures.

Performance evaluation of three liquid chromatography mass spectrometry methods for broad spectrum drug screening.

BACKGROUND: Liquid chromatography-mass spectrometry (LC-MS) and tandem LC-MS (LC-MS/MS) are increasingly used in toxicology laboratories as a complementary method to gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-ultraviolet detection (LC-UV) for comprehensive drug screening (CDS). This study was designed to characterize the sensitivity and specificity of three LC-MS(/MS) vendor-supplied methods for targeted CDS and identify the current limitations associated with the use of these technologies. METHODS: Five methods for broad spectrum CDS, including LC-UV (REMEDi), full scan GC-MS, LC-MS (ZQ-Mass Detector with MassLynx-software), LC-QTRAP-MS/MS (3200-QTRAP with Cliquid-software) and LC-LIT-MS/MS (LXQ Linear Ion Trap with ToxID-software) were evaluated based on their ability to detect drugs in 48 patient urine samples. RESULTS: The tandem MS methods identified 15% more drugs than the single stage MS or LC-UV methods. Use of two broad spectrum screening methods identified more drugs than any single system alone. False negatives and false positives generated by the LC-MS(/MS) software programs were identified upon manual review of the raw data. CONCLUSIONS: The LC-MS/MS methods detected a broader menu of drugs; however, it is essential to establish manual data review criteria for all LC-MS(/MS) drug screening methods. Use of an EI-GC-MS and ESI-LC-MS/MS combination for targeted CDS may be optimal due to the complementary nature of the chromatographic and ionization techniques.

A rapid and fully-automated method for the quantitation of tricyclic antidepressants in serum using turbulent-flow liquid chromatography-tandem mass spectrometry.

BACKGROUND: We describe a fully-automated turbulent-flow liquid chromatography-tandem mass spectrometry method for the detection of tricyclic antidepressant drugs (amitriptyline, desipramine, imipramine, and nortriptyline) in serum. METHODS: Human serum and an internal standard were injected directly onto a Cyclone-P online solid-phase extraction (SPE) column (0.5 x 50 mm). Following removal of serum proteins and other components the analytes were transferred to a Hypersil Gold C-18 (50 x 3 mm) analytical column. Elution occurred with a gradient of water and acetonitrile each with 0.1% formic acid. Analytes were ionized and detected over a 3.5 min analysis time by electrospray-ionization mass spectrometry with selected reaction monitoring (SRM). Matrix effects were well-characterized and carryover, precision, linearity, recovery and limits of detection and quantitation were evaluated. RESULTS: The simple and complex precision CVs for all compounds were < or = 16%. The limits of detection and quantitation for all drugs were < or = 3 ng/ml and <20 ng/ml, respectively. Recoveries were between 97 and 114%. Slopes for method comparison plots were all >0.96. Proficiency testing materials had values within 2 SDI of peer group means for all drugs. CONCLUSION: Based on validation data, this is a specific, sensitive fully-automated method for rapid quantitation of tricyclic antidepressants in serum.

A rapid and reliable method for the quantitation of tricyclic antidepressants in serum using HPLC-MS/MS.

OBJECTIVE: Here we describe a liquid chromatography-tandem mass spectrometry method for the detection of tricyclic antidepressant drugs (amitriptyline, desipramine, imipramine, and nortriptyline) in serum. DESIGN AND METHODS: Following a protein precipitation from serum and dilution of supernatant with water, these analytes and their internal standards (deuterated versions of each drug) were injected, separated, and eluted from a Hypersil Gold C-18 (50x2.1 mm) analytical column with a gradient of water and acetonitrile each with 0.1% formic acid. Analytes were then ionized and detected over a 3.5 minute analysis time by electrospray ionization mass spectrometry with multiple reaction monitoring. Matrix effects were characterized using three methods: post-column infusion, pre- and post-extraction addition of analyte to matrix, and comparison of neet to serum preparations. RESULTS: The inter-day and intra-day coefficients of variation for all compounds were < or =12%. The limit of detection for all drugs was <15 ng/mL and the limit quantitation for all drugs was <22 ng/mL. Recoveries were between 97 and 131% for all drugs. Patient method comparison and proficiency samples were run with acceptable results. CONCLUSION: We have developed a specific and sensitive method for rapid quantitation of tricyclic antidepressants in serum, suitable for use in the clinical laboratory.