Simultaneous determination of zidovudine and lamivudine from rat tissues by liquid chromatography/tandem mass spectrometry

Antiretroviral bioanalysis methods of tissues and body biofluids

Research in the many areas of HIV treatment, eradication and prevention has necessitated measurement of antiretroviral (ARV) concentrations in nontraditional specimen types. To determine the knowledgebase of critical details for accurate bioanalysis, a review of the literature was performed and summarized. Bioanalytical assays for 31 ARVs, including metabolites, were identified in 205 publications measuring various tissues and biofluids. 18 and 30% of tissue or biofluid methods, respectively, analyzed more than one specimen type; 35-37% of the tissue or biofluid methods quantitated more than one ARV. 20 and 76% of tissue or biofluid methods, respectively, were used for the analysis of human specimens. HPLC methods with UV detection predominated, but chronologically MS detection began to surpass. 40% of the assays provided complete intra- and inter-assay validation data, but only 9% of publications provided any stability data with even less for the prevalent ARV in treatments.

Development and validation of an assay for the simultaneous determination of zidovudine, abacavir, emtricitabine, lamivudine, tenofovir and ribavirin in human plasma using liquid chromatography-tandem mass spectrometry

This paper describes the development and validation of an assay for the simultaneous quantification of the antiviral and antiretroviral drugs zidovudine, abacavir, emtricitabine, lamivudine, tenofovir and ribavirin in human plasma using liquid chromatography coupled to tandem mass spectrometry. Sample pretreatment consisted of protein precipitation with 0.1% (v/v) formic acid in methanol, evaporation and reconstitution. Chromatographic separation was performed on a Synergy Polar reversed phase C18 column (150 mm × 2.0 mm ID, particle size 4 μm) using a stepwise gradient with 0.1% (v/v) formic acid in water and 0.1% (v/v) formic acid in methanol at a flow rate of 300 μL/min. A triple quadrupole mass spectrometer operating in the positive ionization mode was used for drug detection and quantification. Isotopically labeled zidovudine, lamivudine, tenofovir and ribavirin were used as internal standards. The method was validated over a clinical range of 20-2500 ng/mL for zidovudine, lamivudine and tenofovir, 4-500 ng/mL for abacavir and emtricitabine and 160-20,000 ng/mL for ribavirin. The inter and intra-assay accuracies and precisions were between -8.47% and 14.2% for zidovudine, emtricitabine and ribavirin. For abacavir, lamivudine and tenofovir, the inter and intra-assay accuracies and precisions at the lower limit of quantification were between -11.0% and 18.3%, whereas at all other levels these accuracies and precisions were between -11.7% and 12.0%. The described method is suitable for the determination of zidovudine, abacavir, emtricitabine, lamivudine, tenofovir and ribavirin in human plasma in clinical practice to monitor plasma concentrations in selected cases to optimize therapy.

Bioanalysis of drug in tissue: current status and challenges

Distribution of drugs into tissues is an important determinant of the overall PK and PD profile. Thus, bioanalysis of drugs and their metabolites in tissues can play an important role in understanding the pharmacological and toxicological properties of new drug candidates. Unlike liquid matrices, bioanalysis in tissues offers unique challenges such as proper tissue sampling, appropriate tissue sample preparation, efficient extraction of the analytes from the tissue homogenates, and demonstration of stability and recovery of analytes in intact tissues. This article provides a systematic review of tissue sample analysis for small molecules using LC–MS/MS. The authors provide rationale for tissue sample analysis, and discuss strategies for method development, method qualification or validation, and sample analysis. Unique aspects of method development and qualification/validation are highlighted based on authors’ direct experiences and literature summary. Analysis using intact tissue samples such as MALDI imaging is also briefly discussed.

Determination of genotoxic alkyl methane sulfonates and alkyl paratoluene sulfonates in lamivudine using hyphenated techniques

Two highly sensitive methods for the determination of genotoxic alkyl methane sulfonates (AMSs) and alkyl paratoluene sulfonates (APTSs) in lamivudine using hyphenated techniques have been presented. AMSs were determined by GC–MS method using GSBP-INOWAX (30 m×0.25 mm×0.25 μm) column. Temperature program was set by maintaining at 100 °C initially for 3 min, then rised to 220 °C at the rate of 15 °C/min and maintained at 220 °C for 16 min. N,N-dimethyl formamide was used as diluent. APTSs were determined by LC-MS using Zorbax, Rx C8, 250 mm×4.6 mm, 5 μm column as stationary phase. 0.01 M ammonium acetate is used as buffer. The mixture of buffer and methanol in 75:25 (v/v) ratio was used as mobile phase A and mixture of buffer and methanol in 5:95 (v/v) ratio was used as mobile phase B. The gradient program (T/%B) was set as 0/28, 16/50, 17/100, 23/100, 27/28 and 40/28. Both the methods were validated as per International Conference on Harmonization guidelines. Limit of quantitation was found 1.5 μg/mL for AMSs and was in the range of 1.0–1.5 μg/mL for APTSs.

Validation of a sensitive LC/MS/MS method for the determination of zidovudine and lamivudine in human plasma

A sensitive LC/MS/MS assay for determining zidovudine (ZDV) and lamivudine (3TC) in human plasma was validated to support antiretroviral pharmacology research programs. After addition of stable labeled isotopic zidovudine (ZDV-IS) and lamivudine (3TC-IS) as internal standard, a solid-phase extraction was performed with an Oasis HLB 1 cm(3) cartridge, with recoveries of 92.3% for ZDV and 93.9% for 3TC. A Phenomonex Synergi Hydro-RP (2.0 ×150 mm) reversed-phase analytical column was utilized for chromatographic separation. The mobile phase consisted of an aqueous solution of 15% acetonitrile and 0.1% acetic acid. Detection was accomplished by ESI/MS/MS in the positive ion mode, monitoring 268/127, 271/130, 230/112 and 233/115 transitions, for ZDV, ZDV-IS, 3TC and 3TC-IS, respectively. The method was linear from 1 to 3000 ng/mL with a minimum quantifiable limit of 1 ng/mL when 100 μL of plasma was analyzed. Validation results demonstrated high accuracy (≤8.3% deviation) and high precision (≤10% CV) for the quality control samples. The method was also shown to be specific and reproducible. The value of the high sensitivity was demonstrated by quantitation of approximately 100 existing samples that had ZDV below the limit of quantitation using a previously validated, less sensitive HPLC-UV method utilized in the laboratory.

Quantification of zidovudine and its monophosphate in cell extracts by on-line solid-phase extraction coupled to liquid chromatography

A simple and rapid analytical method for the simultaneous quantification of zidovudine (AZT) and its monophosphate (AZTMP) in cell extracts has been developed using high-performance liquid chromatography (HPLC) with on-line solid-phase extraction and 2-aminoethyl-3'-azido-2',3'-dideoxythymidin-5'-yl phosphodiester sodium salt as internal standard (IS). The cell extract samples were directly injected on a short reversed-phase precolumn using an aqueous buffer containing an ion-pairing reagent as a mobile phase. Under these conditions, the analytes were retained on the precolumn whereas the proteins were discarded. The analytes were then transferred onto the analytical column by increasing the strength of the eluent. The calibration curve was linear over a concentration range of 0.5-100 microg/ml. Inter- and intra-day accuracy and precision results satisfied the accepted criteria for bioanalytical validation. This method was used to study the decomposition pathway of a model pronucleotide in an in vitro approach.

High throughput LC-MS/MS method for simultaneous quantification of lamivudine, stavudine and nevirapine in human plasma

A selective and high throughput liquid chromatography/tandem mass spectrometry (LC-MS/MS) method has been developed and validated to separate, detect and simultaneously quantify lamivudine (3TC), stavudine (d4T) and nevirapine (NVP) in human plasma using metaxalone as internal standard (IS). After solid phase extraction (SPE), the analytes and the IS were chromatographed on a Symmetry C18 (150 mmx3.9 mm i.d., 5 microm particle size) column using 5 microL injection volume with a run time of 4.5 min. An isocratic mobile phase consisting of 0.5% glacial acetic acid in water:acetonitrile (20:80, v/v) was used to separate all these drugs. The precursor and product ions of these drugs were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring mode (MRM) without polarity switch. The method was validated over the range of 25-3000 ng/mL for 3TC, 20-2000 ng/mL for d4T and 50-5000 ng/mL for NVP. The absolute recoveries for analytes (>or=86%) and IS (98.12%) achieved from spiked plasma samples were consistent and reproducible. Inter-batch and intra-batch precision (%CV) across four validation runs (LLOQ, LQC, MQC and HQC) was less than 10. The accuracy determined at these levels was within +/-8% in terms of relative error. The method was successfully applied to a pivotal bioequivalence study of [60 (3TC)+12 (d4T)+100 (NVP)] mg dispersible tablets in 60 healthy human subjects under fasting condition.

Simultaneous determination of 17 antiretroviral drugs in human plasma for quantitative analysis with liquid chromatography–tandem mass spectrometry

This work describes a sensitive method for the simultaneous determination of 17 antiretroviral drugs including nucleoside analog reverse transcriptase inhibitors, non-nucleoside analog reverse transcriptase inhibitors, protease inhibitors and a nucleotide analog reverse transcriptase inhibitor in 50 microL of human plasma. This method employed high-performance liquid chromatography-tandem mass spectrometry with electrospray ionization. The analytes were monitored in multiple reaction monitoring mode and the polarity was switched from positive to negative to positive to detect all compounds after a single injection. A combination of liquid-liquid extraction and protein precipitation was used to extract all compounds, with at least 75% recovery for all analytes. Within- and between-day accuracies were at least 85% for 1-500 ng/mL for nelfinavir, indinavir and abacavir, 10-500 ng/mL for didanosine and stavudine and 5-500 ng/mL for all other compounds. This method is very effective for quantifying and screening antiretroviral drugs in clinical samples with limited (50 microL) volumes.