High-performance liquid chromatography assay for the quantification of HIV protease inhibitors and non-nucleoside reverse transcriptase inhibitors in human plasma

Semi-quantification and Potency Verification of the HIV Protease Inhibitor Based on the Matrix-Capsid Protein Immobilized Nickel (II)/NTA-Tol/Graphene Oxide/SPCE Electrochemical Biosensor

Human immunodeficiency virus (HIV) causing acquired immune deficiency syndrome (AIDS) is still a global issue. Long-term drug treatment and nonadherence to medication increase the spread of drug-resistant HIV strains. Therefore, the identification of new lead compounds is being investigated and is highly desirable. Nevertheless, a process generally necessitates a significant budget and human resources. In this study, a simple biosensor platform for semi-quantification and verification of the potency of HIV protease inhibitors (PIs) based on electrochemically detecting the cleavage activity of the HIV-1 subtype C-PR (C-SA HIV-1 PR) was proposed. An electrochemical biosensor was fabricated by immobilizing His6-matrix-capsid (H₆MA-CA) on the electrode surface via the chelation to Ni²⁺-nitrilotriacetic acid (NTA) functionalized GO. The functional groups and the characteristics of modified screen-printed carbon electrodes (SPCE) were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). C-SA HIV-1 PR activity and the effect of PIs were validated by recording changes in electrical current signals of the ferri/ferrocyanide redox probe. The detection of PIs, i.e., lopinavir (LPV) and indinavir (IDV), toward the HIV protease was confirmed by the decrease in the current signals in a dose-dependent manner. In addition, our developed biosensor demonstrates the ability to distinguish the potency of two PIs to inhibit C-SA HIV-1 PR activities. We anticipated that this low-cost electrochemical biosensor would increase the efficiency of the lead compound screening process and accelerate the discovery and development of new HIV drugs.

A fast-screening dispersive liquid-liquid microextraction-gas chromatography-mass spectrometry method applied to the determination of efavirenz in human plasma samples

We demonstrate the suitability of a fast, green, easy-to-perform, and modified sample extraction procedure, i.e., dispersive liquid-liquid microextraction (DLLME) for the determination of efavirenz (EFV) in human plasma. Data acquisition was done by gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring (SIM) mode. The simplicity of the method lies in, among others, the avoidance of the use of large organic solvent volumes as mobile phases and non-volatile buffers that tend to block the plumbing in high-performance liquid chromatography (HPLC). Chromatographic and mass spectral parameters were optimized using bovine whole blood for matrix matching due to insufficient human plasma. Method validation was accomplished using the United States Food and Drug Administration (USFDA) 2018 guidelines. The calibration curve was linear with a dynamic range of 0.10-2.0 μg/mL and an R² value of 0.9998. The within-run accuracy and precision were both less than 20% at the lower limit of quantification (LLOQ) spike level. The LLOQ was 0.027 μg/mL which compared well with some values but was also orders of magnitude better than others reported in the literature. The percent recovery was 91.5% at the LLOQ spike level. The DLLME technique was applied in human plasma samples from patients who were on treatment with EFV. The human plasma samples gave concentrations of EFV ranging between 0.14-1.00 μg/mL with three samples out of seven showing concentrations that fell within or close to the recommended therapeutic range.

Human Immunodeficiency Virus Type 1 RNA Detected in the Central Nervous System (CNS) After Years of Suppressive Antiretroviral Therapy Can Originate from a Replicating CNS Reservoir or Clonally Expanded Cells

BACKGROUND

Human immunodeficiency virus type 1 (HIV-1) populations are detected in cerebrospinal fluid (CSF) of some people on suppressive antiretroviral therapy (ART). Detailed analysis of these populations may reveal whether they are produced by central nervous system (CNS) reservoirs.

METHODS

We performed a study of 101 asymptomatic participants on stable ART. HIV-1 RNA concentrations were cross-sectionally measured in CSF and plasma. In participants with CSF HIV-1 RNA concentrations sufficient for analysis, viral populations were genetically and phenotypically characterized over multiple time points.

RESULTS

For 6% of participants (6 of 101), the concentration of HIV-1 RNA in their CSF was ≥0.5 log copies/mL above that of plasma (ie, CSF escape). We generated viral envelope sequences from CSF of 3 participants. One had a persistent CSF escape population that was macrophage-tropic, partially drug resistant, genetically diverse, and closely related to a minor macrophage-tropic lineage present in the blood prior to viral suppression and enriched for after ART. Two participants (1 suppressed and 1 not) had transient CSF escape populations that were R5 T cell-tropic with little genetic diversity.

CONCLUSIONS

Extensive analysis of viral populations in 1 participant revealed that CSF escape was from a persistently replicating population, likely in macrophages/microglia, present in the CNS over 3 years of ART. CSF escape in 2 other participants was likely produced by trafficking and transient expansion of infected T cells in the CNS. Our results show that CNS reservoirs can persist during ART and that CSF escape is not exclusively produced by replicating CNS reservoirs.

Predicting Efavirenz Concentrations in the Brain Tissue of HIV-Infected Individuals and Exploring their Relationship to Neurocognitive Impairment

Sparse data exist on the penetration of antiretrovirals into brain tissue. In this work, we present a framework to use efavirenz (EFV) pharmacokinetic (PK) data in plasma, cerebrospinal fluid (CSF), and brain tissue of eight rhesus macaques to predict brain tissue concentrations in HIV-infected individuals. We then perform exposure-response analysis with the model-predicted EFV area under the concentration-time curve (AUC) and neurocognitive scores collected from a group of 24 HIV-infected participants. Adult rhesus macaques were dosed daily with 200 mg EFV (as part of a four-drug regimen) for 10 days. Plasma was collected at 8 time points over 10 days and at necropsy, whereas CSF and brain tissue were collected at necropsy. In the clinical study, data were obtained from one paired plasma and CSF sample of participants prescribed EFV, and neuropsychological test evaluations were administered across 15 domains. PK modeling was performed using ADAPT version 5.0 Biomedical Simulation Resource, Los Angeles, CA) with the iterative two-stage estimation method. An eight-compartment model best described EFV distribution across the plasma, CSF, and brain tissue of rhesus macaques and humans. Model-predicted median brain tissue concentrations in humans were 31 and 8,000 ng/mL, respectively. Model-predicted brain tissue AUC was highly correlated with plasma AUC (γ = 0.99, P < 0.001) but not CSF AUC (γ = 0.34, P = 0.1) and did not show any relationship with neurocognitive scores (γ < 0.05, P > 0.05). This analysis provides an approach to estimate PK the brain tissue in order to perform PK/pharmacodynamic analyses at the target site.

Population Pharmacokinetics Modeling of Unbound Efavirenz, Atazanavir, and Ritonavir in HIV-Infected Subjects With Aging Biomarkers

Unbound drug is the pharmacodynamically relevant concentration. This study aimed to determine if chronologic age or markers of biologic aging, such as the frailty phenotype and p16INK4a gene expression, altered unbound pharmacokinetics (PKs) of efavirenz (EFV) and atazanavir/ritonavir (ATV/RTV). Sixty human immunodeficiency virus (HIV)-infected participants receiving EFV and 31 receiving ATV/RTV provided 1 to 11 samples to quantify total and unbound plasma concentrations. Population PK models with total and unbound concentrations simultaneously described are developed for each drug. The unbound fractions for EFV, ATV, and RTV are 0.65%, 5.67%, and 0.63%, respectively. Covariate analysis suggests RTV unbound PK is sensitive to body size; unbound fraction of RTV is 34% lower with body mass index (BMI) above 30 kg/m2 . No alterations in drug clearance or unbound fraction with age, frailty, or p16INK4a expression were observed. Assessing functional and physiologic aging markers to inform potential PK changes is necessary to determine if drug/dosing changes are warranted in the aging population.

Therapeutic drug monitoring of antiretroviral drugs in HIV-infected patients

INTRODUCTION

Therapeutic drug monitoring (TDM) may be beneficial when applied to antiretroviral (ARV). Even though TDM can be a valuable strategy in HIV management, its role remains controversial. Areas covered: This review provides a comprehensive update on important issues relating to TDM of ARV drugs in HIV-infected patients. Articles from PubMed with keywords relevant to each topic section were reviewed. Search strategies limited to articles published in English. Expert commentary: There is evidence supporting the use of TDM in HIV treatment. However, some limitations need to be considered. The evidence supporting the use of routine TDM for all patients is limited, as it is not clear that this strategy offers any advantages over TDM for selected indications. Selected groups of patients including patients with physiological changes, patients with drug-drug interactions or toxicity, and the elderly could potentially benefit from TDM, as optimized dosing is challenging in these populations.

Tenofovir/emtricitabine metabolites and endogenous nucleotide exposures are associated with p16(INK4a) expression in subjects on combination therapy

BACKGROUND

HIV may amplify immunological, physiological and functional changes of ageing. We determined associations of frailty phenotype, a T-cell senescence marker (p16(INK4a) expression), age and demographics with exposures of the intracellular metabolites (IM) and endogenous nucleotides (EN) of tenofovir/emtricitabine (TFV/FTC), efavirenz (EFV), atazanavir (ATV) and ritonavir (RTV).

METHODS

Plasma and peripheral blood mononuclear cell samples for drug, IM and EN concentrations were collected at four time points in HIV+ adults receiving TFV/FTC with EFV or ATV/RTV. Subjects underwent frailty phenotyping and p16(INK4a) expression analysis. Non-compartmental analysis generated an area under the curve (AUC) for each analyte. Spearman rank correlation and Kruskal-Wallis tests were used to assess associations between AUC, demographics and ageing markers, adjusting for multiple comparisons with the Holm procedure.

RESULTS

Subjects (n=79) ranged in age from 22-73 years (median 48 years); 48 were African-American, 24 were female, 54 received EFV. Three subjects (range 51-60 years) demonstrated frailty, with 17 subjects (range 26-60 years) demonstrating pre-frailty. Negative associations were observed between p16(INK4a) expression and each of FTC-triphosphate (r=-0.45), deoxyadenosine triphosphate (dATP; r=-0.47) and deoxycytidine triphosphate (dCTP; r=-0.57) AUCs (P-values <0.02). TFV and FTC AUCs were larger among subjects with lower renal function or higher chronological age (P-values ≤0.05). No associations were observed for EFV, ATV or RTV AUCs.

CONCLUSIONS

Associations of IM/EN exposure and p16(INK4a) expression observed here suggest that senescence may alter drug phosphorylation, metabolism or transport. This finding warrants further mechanistic study to ensure optimal treatment in the ageing HIV+ population. Clinicaltrials.gov NCT01180075.

A simple, rapid, economical, and practical method for the determination of efavirenz in plasma of Chinese AIDS patients by reverse phase high-performance liquid chromatography with ultraviolet detector

This study aimed to develop a reverse phase high-performance liquid chromatographic (RP-HPLC) method for the determination of efavirenz in human plasma and to use it for determining the concentrations of efavirenz in Chinese AIDS patient. A simple mobile phase consisting of 0.01 mol/L NaH2PO4 solution and acetonitrile (38:62, V/V) was pumped at a flow rate of 1.0 mL/min through a reverse phase Diamonsil C18 column maintained at 30°C. Diazepam was used as an internal standard and monitored with efavirenz at 247 nm. The protein of 100 μL plasma sample was precipitated before 20 μL of the supernatant was directly injected into the column. The linear response over the concentration ranges 0.10-20.0 μg/mL was obtained and the linear regression equations was Y = 2.2873X ‒ 0.1449 (r = 0.9999). The intra-day and inter-day precisions (1.9-2.6%, 2.2-7.2%, respectively), the relative and absolute recovery (99.3-106.3%, 75.6-80.3%, respectively) met the international standards. Stability of plasma samples were evaluated for short-term (ambient temperature for 16 h) and long-term (-20°C for 30 days) storage conditions and were found to be stable. The mean plasma concentration of efavirenz of the 406 patients was 2.21 ± 1.95 μg/mL, 77.3% of which were within the therapeutic window (1-4 μg/mL), 15.1% were below the window, and 7.6% were over it. In conclusion, the method had advantages of convenience, rapidity, necessary accuracy and precision, high practicality and met the needs for therapeutic drug monitoring and the pharmacokinetic study of efavirenz, especially in underdeveloped countries. For Chinese AIDS patients, it was beneficial to use efavirenz under the guidance of therapeutic drug monitoring.

A sensitive and selective liquid chromatography/tandem mass spectrometry method for quantitative analysis of efavirenz in human plasma

A selective and a highly sensitive method for the determination of the non-nucleoside reverse transcriptase inhibitor (NNRTI), efavirenz, in human plasma has been developed and fully validated based on high performance liquid chromatography tandem mass spectrometry (LC-MS/MS). Sample preparation involved protein precipitation followed by one to one dilution with water. The analyte, efavirenz was separated by high performance liquid chromatography and detected with tandem mass spectrometry in negative ionization mode with multiple reaction monitoring. Efavirenz and ¹³C₆-efavirenz (Internal Standard), respectively, were detected via the following MRM transitions: m/z 314.20243.90 and m/z 320.20249.90. A gradient program was used to elute the analytes using 0.1% formic acid in water and 0.1% formic acid in acetonitrile as mobile phase solvents, at a flow-rate of 0.3 mL/min. The total run time was 5 min and the retention times for the internal standard (¹³C₆-efavirenz) and efavirenz was approximately 2.6 min. The calibration curves showed linearity (coefficient of regression, r>0.99) over the concentration range of 1.0-2,500 ng/mL. The intraday precision based on the standard deviation of replicates of lower limit of quantification (LLOQ) was 9.24% and for quality control (QC) samples ranged from 2.41% to 6.42% and with accuracy from 112% and 100-111% for LLOQ and QC samples. The inter day precision was 12.3% and 3.03-9.18% for LLOQ and quality controls samples, and the accuracy was 108% and 95.2-108% for LLOQ and QC samples. Stability studies showed that efavirenz was stable during the expected conditions for sample preparation and storage. The lower limit of quantification for efavirenz was 1 ng/mL. The analytical method showed excellent sensitivity, precision, and accuracy. This method is robust and is being successfully applied for therapeutic drug monitoring and pharmacokinetic studies in HIV-infected patients.

Pharmacokinetic modelling of efavirenz, atazanavir, lamivudine and tenofovir in the female genital tract of HIV-infected pre-menopausal women

BACKGROUND AND OBJECTIVES

A previously published study of antiretroviral pharmacokinetics in the female genital tract of HIV-infected women demonstrated differing degrees of female genital tract penetration among antiretrovirals. These blood plasma (BP) and cervicovaginal fluid (CVF) data were co-modelled for four antiretrovirals with varying CVF exposures.

METHODS

Six paired BP and CVF samples were collected over 24 h, and antiretroviral concentrations determined using validated liquid chromatography (LC) with UV detection or LC-mass spectrometry analytical methods. For each antiretroviral, a BP model was fit using Bayesian estimation (ADAPT5), followed by addition of a CVF model. The final model was chosen based on graphical and statistical output, and then non-linear mixed-effects modelling using S-ADAPT was performed. Population mean parameters and their variability are reported. Model-predicated area under the concentration-time curve during the dosing interval (AUC(τ)) and exposure ratios of CVF AUC(τ):BP AUC(τ) were calculated for each drug.

RESULTS

The base model uses first-order absorption with a lag time, a two-compartment model, and a series of transit compartments that transfer the drug from BP to CVF. Protein-unbound drug transfers into CVF for efavirenz and atazanavir; total drug transfers for lamivudine and tenofovir. CVF follows a one-compartment model for efavirenz and atazanavir, and a two-compartment model for lamivudine and tenofovir. As expected, inter-individual variability was high. Model-predicted CVF AUC(τ):BP AUC(τ) ratios are consistent with published results.

CONCLUSIONS

This is the first pharmacokinetic modelling of antiretroviral disposition in BP and CVF. These models will be further refined with tissue data, and used in clinical trials simulations to inform future studies of HIV pre-exposure prophylaxis in women.

Pharmacokinetics of two common antiretroviral regimens in older HIV-infected patients: a pilot study

OBJECTIVES

The pharmacokinetics (PK) of antiretrovirals (ARVs) in older HIV-infected patients are poorly described. Here, the steady-state PK of two common ARV regimens [tenofovir (TFV)/emtricitabine (FTC)/efavirenz (EFV) and TFV/FTC/atazanavir (ATV)/ritonavir (RTV)] in older nonfrail HIV-infected patients are presented.

METHODS

HIV-infected subjects ≥ 55 years old not demonstrating the frailty phenotype were enrolled in an unblinded, intensive-sampling PK study. Blood plasma (for TFV, FTC, EFV, ATV and RTV concentrations) and peripheral blood mononuclear cells [PBMCs; for tenofovir diphosphate (TFV-DP) and emtricitabine triphosphate (FTC-TP) concentrations] were collected at 11 time-points over a 24-hour dosing interval. Drug concentrations were analysed using validated liquid chromatography-ultraviolet detection (LC-UV) or liquid chromatography tandem mass spectrometry (LC-MS/MS) methods. Noncompartmental pharmacokinetic analysis was used to estimate PK parameters [area under the concentration-time curve over 24 h (AUC0-24h ) and maximal concentration (Cmax )]. These parameters were compared with historical values from the general HIV-infected population.

RESULTS

Six subjects on each regimen completed the study. Compared with the general population, these elderly subjects had 8-13% decreased TFV AUC0-24h and Cmax , and 19-78% increased FTC and RTV AUC0-24h and Cmax . Decreased ATV AUC0-24h (12%) and increased Cmax (9%) were noted, while EFV exposure was unchanged (5%) with a 16% decrease in Cmax . Intracellular nucleoside/tide metabolite concentrations and AUC are also reported for these subjects.

CONCLUSIONS

This study demonstrates that the PK of these ARVs are altered by 5-78% in an older HIV-infected population. Implications of PK differences for clinical outcomes, particularly with the active nucleoside metabolites, remain to be explored. This study forms the basis for further study of ARV PK, efficacy, and toxicity in older HIV-infected patients.

Development and validation of a normal-phase HPTLC method for the simultaneous analysis of Lamivudine and Zidovudine in fixed-dose combination tablets

Simultaneous quantification of Lamivudine and Zidovudine in tablets by HPTLC method was developed and validated. The chromatograms were developed using a mobile phase of toluene:ethyl acetate:methanol (4:4:2, v/v/v) on pre-coated plate of silica gel GF aluminum TLC plate and quantified by densitometric absorbance mode at 276 nm. The R_f values were 0.41±0.03 and 0.60±0.04 for Lamivudine and Zidovudine, respectively. The linearity of the method was found to be within the concentration range of 50−250 ng/spot for Lamivudine and for Zidovudine, it was 100−500 ng/spot. The lower limits of detection and quantification were 2.23 ng/spot and 7.90 ng/spot for Lamivudine and 2.90 ng/spot and 8.85 ng/spot for Zidovudine. The method was also validated for precision, specificity and recovery. This developed method was used to analyze fixed-dose tablets (Duovir, Cipla Ltd) samples of Lamivudine and Zidovudine.

Therapeutic drug monitoring in highly active antiretroviral therapy

IMPORTANCE OF THE FIELD

Despite the efficacy of combination antiretroviral therapy (ART), a large proportion of patients living with HIV/AIDS on ART does not achieve or maintain adequate virological suppression. Therapeutic drug monitoring (TDM) has been utilised to improve treatment outcomes of ART.

AREAS COVERED IN THE REVIEW

The potential incorporation of TDM into the clinical HIV management is supported by the existing relationship between drug exposure and efficacy/toxicity, the high inter-patient variability pharmacokinetics, and the accurate, specific and rapid method for drug level determination. The current status of TDM in ART is reviewed in this article with discussions on its feasibility, potential use and limitations.

WHAT THE READER WILL GAIN

Mounting evidence from clinical trials has indicated the potential use of TDM in reducing the rates of treatment failure and adverse effect, avoiding the drug interactions, and special populations, such as children, pregnant women and patients with co-infections. TDM may play an important role even in resource-limited settings, to safeguard expanded use of bioequivalent generic antiretroviral drugs and avoid drug interactions with traditional Chinese medicines.

TAKE HOME MESSAGE

TDM is still in the centre of controversy in that several critical issues need to be addressed, such as limited adherence assessment, inappropriate response predictors, insufficient validation of target concentration windows and lack of the quality control of assay. The utility of TDM will remain experimental until more data are obtained from large clinical trials showing the benefit of TDM.

Comparison of once-daily versus twice-daily combination antiretroviral therapy in treatment-naive patients: results of AIDS clinical trials group (ACTG) A5073, a 48-week randomized controlled trial

BACKGROUND

Dosing frequency is an important determinant of regimen effectiveness. Methods. To compare efficacy of once-daily (QD) versus twice-daily (BID) antiretroviral therapy, we randomized human immunodeficiency virus (HIV)-positive, treatment-naive patients to lopinavir-ritonavir (LPV/r) administered at a dosage of 400 mg of lopinavir and 100 mg of ritonavir BID (n = 160) or 800 mg of lopinavir and 200 mg of ritonavir QD (n = 161), plus either emtricitabine 200 mg QD and extended-release stavudine at a dosage of 100 mg QD or tenofovir at a dosage of 300 mg QD. Randomization was stratified by screening HIV RNA level <100,000 copies/mL versus > or = 100,000 copies/mL. The primary efficacy end point was sustained virologic response (SVR; defined as reaching and maintaining an HIV RNA level <200 copies/mL) through week 48.

RESULTS

Subjects were 78% male, 33% Hispanic, and 34% black. A total of 82% of subjects completed the study, and 71% continued to receive the initially assigned dosage schedule. The probability of SVR did not differ significantly for the BID versus QD comparison, with an absolute proportional difference of 0.03 (95% confidence interval [CI], -0.07 to 0.12). The comparison depended on the screening RNA stratum (P=.038); in the higher RNA stratum, the probability of SVR was significantly better in the BID arm than in the QD arm: 0.89 (95% CI, 0.79-0.94) versus 0.76 (95% CI, 0.64-0.84), a difference of 0.13 (95% CI, 0.01-0.25). Lopinavir trough plasma concentrations were higher with BID dosing. Adherence to prescribed doses of LPV/r was 90.6% in the QD arm versus 79.9% in the BID arm (P<.001). Conclusions. Although subjects assigned to QD regimens had better adherence, overall treatment outcomes were similar in the QD and BID arms. Subjects with HIV RNA levels > or =100,000 copies/mL had better SVR with BID regimens at 48 weeks, which suggests a possible advantage in this setting for more frequent dosing. Clinical trial registration. ClinicalTrials.gov registration number: NCT00036452.

An accurate and precise high-performance liquid chromatography method for the rapid quantification of the novel HIV integrase inhibitor raltegravir in human blood plasma after solid phase extraction

The quantification of the HIV integrase inhibitor raltegravir in blood plasma is described using solid phase extraction (SPE) coupled with an accurate high-performance liquid chromatography assay with ultraviolet (UV) detection. The method was validated over the range of 20-10,000 ng/mL using simple sample preparation and chromatography. The SPE method was optimized to be selective and highly efficient. The buffer's ionic strength and pH were optimized for retaining RAL and the internal standard on the column, the percentage of methanol was optimized in the cleaning step to remove unwanted plasma contaminants, and the type and amount of acid was optimized for complete elution of the compounds. This method has no interference with other potentially co-administered antiretrovirals or common drugs. Average recoveries for the extraction method were consistently high: 90% for raltegravir and 90% for the internal standard diazepam. This method was found to be accurate and precise. Within day (n=6) and between day (n=18) accuracies ranged from 97.5 to 104.4%. Within-day (n=6) and between-day (n=18) precision ranged from 1.4 to 3.8%, and from 2.4 to 7.9%, respectively. This is the first published method to use simple UV technology and reliable SPE extraction methodology for the quantification of raltegravir in human plasma. This method can be easily implemented in most bioanalytical laboratories.

Effects of minocycline and valproic acid coadministration on atazanavir plasma concentrations in human immunodeficiency virus-infected adults receiving atazanavir-ritonavir

Minocycline and valproic acid are potential adjuvant therapies for the treatment of human immunodeficiency virus (HIV)-associated cognitive impairment. The purpose of this study was to determine whether minocycline alone or in combination with valproic acid affected atazanavir plasma concentrations. Twelve adult HIV-infected subjects whose regimen included atazanavir (300 mg)-ritonavir (100 mg) daily for at least 4 weeks were enrolled. Each subject received atazanavir-ritonavir on day 1, atazanavir-ritonavir plus 100 mg minocycline twice daily on days 2 to 15, and atazanavir-ritonavir plus 100 mg minocycline twice daily and 250 mg valproic acid twice daily on days 16 to 30 with meals. The subjects had 11 plasma samples drawn over a dosing interval on days 1, 15, and 30. The coadministration of minocycline and valproic acid with atazanavir-ritonavir was well tolerated in all 12 subjects (six male; mean [+/- standard deviation] age was 43.1 [8.2] years). The geometric mean ratios (GMRs; 95% confidence interval [CI]) for the atazanavir area under the concentration-time curve from 0 to 24 h at steady state (AUC(0-24)), the plasma concentration 24 h after the dose (C(min)), and the maximum concentration during the dosing interval (C(max)) with and without minocycline were 0.67 (0.50 to 0.90), 0.50 (0.28 to 0.89), and 0.75 (0.58 to 0.95), respectively. Similar decreases in atazanavir exposure were seen after the addition of valproic acid. The GMRs (95% CI) for atazanavir AUC(0-24), C(min), and C(max) with and without minocycline plus valproic acid were 0.68 (0.43 to 1.06), 0.50 (0.24 to 1.06), and 0.66 (0.41 to 1.06), respectively. Coadministration of neither minocycline nor minocycline plus valproic acid appeared to influence the plasma concentrations of ritonavir (P > 0.2). Minocycline coadministration resulted in decreased atazanavir exposure, and there was no evidence that the addition of valproic acid mediated this effect.

Effect of omeprazole on the plasma concentrations of indinavir when administered alone and in combination with ritonavir

PURPOSE

The effects of omeprazole on indinavir when administered alone or in combination with ritonavir were evaluated.

METHODS

Fourteen men and women age 18-55 years not infected with human immunodeficiency virus who met study qualifications were randomized to receive placebo, 20 mg of omeprazole, or 40 mg of omeprazole daily. After seven days, the single-dose pharmacokinetic profile of an 800-mg dose of indinavir alone or in combination with 200 mg of ritonavir was evaluated. Study participants received each of four study regimens in one of four randomly assigned orders. Blood samples were collected, and plasma indinavir and ritonavir concentrations were analyzed using high-performance liquid chromatography.

RESULTS

The coadministration of 20 or 40 mg of omeprazole with indinavir significantly reduced the mean indinavir area under the concentration-versus-time curve (AUC) from 30.0 mg x hr/L (95% confidence interval [CI], 21.9-41.1 mg x hr/L) to 19.7 mg x hr/L (95% CI, 14.6-26.8 mg x hr/L) or 16.0 mg x hr/L (95% CI, 11.8-21.7 mg x hr/L), respectively (p < 0.002). The addition of 200 mg of ritonavir to 800 mg of indinavir in combination with 40 mg of omeprazole significantly increased the mean indinavir AUC from 30.0 mg x hr/L (95% CI, 21.9-41.1 mg x hr/L) to 46.6 mg x hr/L (95% CI, 34.0-63.8 mg x hr/L), but it did not significantly affect mean omeprazole concentrations (p < or = 0.02).

CONCLUSION

The AUC of indinavir was substantially decreased in healthy volunteers who received omeprazole 20 or 40 mg daily for seven days before the administration of a single 800-mg dose of indinavir. Concomitant administration of ritonavir 200 mg with indinavir in participants receiving omeprazole led to a significant increase in the AUC of indinavir.

Quantitation of five nevirapine oxidative metabolites in human plasma using liquid chromatography–tandem mass spectrometry

A multiple-reaction-monitoring LC/MS/MS method for the analysis of nevirapine oxidative metabolites, 2-hydroxynevirapine, 3-hydroxynevirapine, 8-hydroxynevirapine, 12-hydroxynevirapine, and 4-carboxynevirapine, in human plasma was developed and validated. The metabolites were isolated from 50 microL heparinized plasma by enzymatic hydrolysis of the glucuronide conjugates to the free metabolite followed by protein precipitation with acetonitrile. Peaks were quantitated at 3.03 min for the 4-carboxynevirapine metabolite, at 3.72, 4.27, 5.27, and 5.73 min for the positional 2-hydroxynevirapine, 12-hydroxynevirapine, 3-hydroxynevirapine, and 8-hydroxynevirapine metabolites, respectively, and 2.30 min for the internal standard, pirenzepine. The assay was accurate and precise based on assay validation controls over the nominal range of 0.010-1.0 mg/L. The average accuracy at the lowest concentration quality control (QC) sample was 16% (difference from theoretical value) for 8-hydroxynevirapine, all others were closer to their known respective standards. Within- and between-day precisions were within 12% for quality control samples for all five metabolites. Repetitive thawing and freezing did not have an effect on any metabolite through a minimum of three cycles. Thawed samples, remaining in plasma for 4 h before extraction, were within 5% of theoretical value. Stability of the extracted samples on the autosampler at room temperature was evaluated for 48 h and was observed to be within 12% of a fresh analytical sample for 2-hydroxynevirapine and 3-hydroxynevirapine; other metabolites were within 6% of theoretical value. The utility of the analytical method was demonstrated using trough steady-state plasma samples collected from 48 patients in a hepatic impairment study.

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.

High-performance liquid chromatography assay for the determination of the HIV-protease inhibitor tipranavir in human plasma in combination with nine other antiretroviral medications

An accurate, sensitive and simple reverse-phase (RP) high-performance liquid chromatography (HPLC) assay has been developed and validated for the simultaneous quantitative determination of tipranavir with nine other antiretroviral drugs in plasma. A liquid-liquid extraction of the drugs in tert-butylmethylether (TBME) from 200 microL of plasma is followed by a reversed phase gradient HPLC assay with UV detection at 210 nm. The standard curve for the drug was linear in the range of 80-80,000 ng/mL for tipranavir; 10-10,000 ng/mL for nevirapine, indinavir, efavirenz, and saquinavir; and 25-10,000 ng/mL for amprenavir, atazanavir, ritonavir, lopinavir, and nelfinavir. The regression coefficient (r(2)) was greater than 0.998 for all analytes. This method has been fully validated and shown to be specific, accurate and precise. Due to an excellent extraction procedure giving good recovery and a clean baseline, this method is simple, rapid, accurate and provides excellent resolution and peak shape for all analytes. Thus this method is very suitable for therapeutic drug monitoring.

Pharmacokinetic comparison of generic and trade formulations of lamivudine, stavudine and nevirapine in HIV-infected Malawian adults

BACKGROUND

The Malawian antiretroviral program uses generic Triomune (stavudine, lamivudine, and nevirapine).

OBJECTIVE

To determine the pharmacokinetics and bioequivalence of generic and trade formulations of stavudine, lamivudine, and nevirapine in HIV-infected Malawians.

METHODS

This randomized, open label, cross-over study comprised of six men and six women currently receiving Triomune-40 TM who were randomized to the generic or trade formulation of stavudine (40 mg twice daily), lamivudine (150 mg twice daily) and nevirapine (200 mg twice daily). After at least 21 days, the alternate formulation was administered. At the end of each period, six blood samples were collected over 8 h. Bioequivalence was achieved if the 90% confidence interval (CI) for the geometric mean ratio (GMR) of generic:trade formulations for maximum plasma concentration (Cmax) and the area under the concentration-time curve (AUC) was within 0.8-1.25.

RESULTS

Mean patient age, weight, and height were 38.4 years (SD, 7.7), 71.2 kg (SD, 7.0), and 164.8 cm (SD, 6.3), respectively. The GMR for stavudine, lamivudine, and nevirapine were 1.4 (90% CI, 1.2-1.7), 1.1 (90% CI, 0.8-1.6), and 0.9 (90% CI, 0.7-1.2), respectively, for Cmax; and 1.1 (90% CI, 1.0 1.2), 1.0 (90% CI, 0.7-1.3), and 0.9 (90% CI, 0.7-1.1), respectively, for AUC0-8h. Regardless of formulation, Malawians had higher nevirapine exposures compared with historical reports of Western HIV-infected patients.

CONCLUSIONS

Although exposures were similar, Triomune did not meet the strict definition of bioequivalence for these drugs. Patients taking Triomune had notably higher stavudine Cmax values. Antiretroviral pharmacokinetics and bioequivalence of generic formulations should be evaluated in the populations in which they are being used.

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.

Simultaneous determination of 8 HIV protease inhibitors in human plasma by isocratic high-performance liquid chromatography with combined use of UV and fluorescence detection: Amprenavir, indinavir, atazanavir, ritonavir, lopinavir, saquinavir, nelfinavir and M8-nelfinavir metabolite

A simple, accurate and fast method was developed for determination of the commonly used HIV protease inhibitors (PIs) amprenavir, indinavir, atazanavir, ritonavir, lopinavir, nelfinavir, M8-nelfinavir metabolite and saquinavir in human plasma. Liquid-liquid extraction was used with hexane/ethylacetate from buffered plasma samples with a borate buffer pH 9.0. Isocratic chromatographic separation of all components was performed on an Allsphere hexyl HPLC column with combined UV and fluorescence detection. Calibration curves were constructed in the range of 0.025-10 mg/l. Accuracy and precision of the standards were all below 15% and the lowest limit of quantitation was 0.025 mg/l. Stability of quality control samples at different temperature conditions was found to be below 20% of nominal values. The advantages of this method are: (1) inclusion and determination of the newly approved atazanavir, (2) simultaneous isocratic HPLC separation of all compounds and (3) increased specificity and sensitivity for amprenavir by using fluorescence detection. This method can be used for therapeutic drug monitoring of all PIs currently commercialised and is now part of current clinical practice.

A novel validated LC method for quantitation of lopinavir in bulk drug and pharmaceutical formulation in the presence of its potential impurities and degradation products

A simple isocratic liquid chromatographic method was developed for determination of lopinavir from its related impurities and assay for the first time. This method involves the use of a C(8) (Symmetry Shield RP8, 150 x 4.6 mm, 5 microm) column. The method was validated over the range of limit of quantitation (LOQ) to 120% of impurity specification limit and LOQ to 150% of working concentration for assay. The mobile phase consisted of a mixture of 50 mM of potassium phosphate buffer, acetonitrile and methanol in the ratio of 40:50:10. The flow rate was set at 1.0 mL/min with UV detection monitored at 210 nm. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. The developed method was validated for linearity, range, precision, accuracy and specificity. This method was successfully applied for content determination of lopinavir in pharmaceutical formulations. The method can be conveniently used in a quality control laboratory for routine analysis for assay and related substances as well for the evaluation of stability samples of bulk drugs and pharmaceutical formulations.

Full validation of an analytical method for the HIV-protease inhibitor atazanavir in combination with 8 other antiretroviral agents and its applicability to therapeutic drug monitoring

Because HIV medications are used in combination, it is important to develop multiplex assays to streamline the therapeutic drug monitoring process and provide rapid turnaround. This article reports full validation of an analytical method that combines atazanavir with 6 HIV-protease inhibitors (indinavir, amprenavir, saquinavir, nelfinavir, ritonavir, and lopinavir) and 2 nonnucleoside reverse transcriptase inhibitors (nevirapine and efavirenz). Using 200 microL of plasma and a simple liquid-liquid extraction method, this analytical method achieved a clean baseline and high extraction efficiencies (90.0% to 99.5%). A Zorbax C-18 (150 x 4.6 mm, 3.5 microm) analytical column was used along with a 27-minute linear gradient elution of the mobile phase to provide sharp peaks at 210 nm. This method was validated over a range of 25 to 10,000 ng/mL and is accurate (90.4% to 110.5%) and precise (precision within a day and between days ranged from 2.3% to 8.3%). Because this method is simple and inexpensive, it may have applicability in countries with low resources.

An isocratic liquid chromatography method for determining HIV non-nucleoside reverse transcriptase inhibitor and protease inhibitor concentrations in human plasma

An efficient, isocratic high performance liquid chromatography (HPLC) method for determining human immunodeficiency virus (HIV) non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs) in plasma is advantageous for laboratories participating in clinical trials and therapeutic drug monitoring (TDM) programs, or conducting small animal research. The combination of isocratic reversed phase chromatography using an S-3, 3.0 mm x 150 mm column along with low plasma volume (200 microl), rapid liquid-liquid extraction, and detection at a single wavelength (212 nm) over a short run time makes this method valuable. Within and between assay variability ranges from 0.8 to 3.5% and 1.2-6.2%, respectively. Accuracy ranges from 91.0 to 112.8% for four quality controls (50, 100, 1000, and 10,000 ng/ml) for all drugs measured (efavirenz, nevirapine, amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir).

Evaluation of an International Pharmacopoeia method for the analysis of indinavir sulfate by liquid chromatography

A gradient LC method for the determination of indinavir sulfate (IDV) and its impurities has been recently published in a consultation document of the International Pharmacopoeia, WHO Drug Information. The method uses a base-deactivated reversed-phase C18 column (25 cm x 4.6 mm i.d.), 5 microm kept at a temperature of 40 degrees C. The mobile phases consist of acetonitrile, phosphate buffer pH 7.5 and water. The flow rate is 1.0 ml/min. UV detection is performed at 220 nm. A system suitability test (SST) is described to govern the quality of the separation. The separation towards IDV components was investigated on 16 C18 columns and correlation was made with the column classification system developed in our laboratory. The method was evaluated using a Hypersil BDS C18 column (25 cm x 4.6 mm i.d.), 5 microm. A central composite design was applied to examine the robustness of the method. The method shows good precision, linearity, sensitivity and robustness. Six commercial samples were examined using this method.

Lopinavir/ritonavir induces the hepatic activity of cytochrome P450 enzymes CYP2C9, CYP2C19, and CYP1A2 but inhibits the hepatic and intestinal activity of CYP3A as measured by a phenotyping drug cocktail in healthy volunteers

OBJECTIVE

The effect of lopinavir/ritonavir (LPV/r) administration on cytochrome P450 (CYP) enzyme activity was quantified using a phenotyping biomarker cocktail. Changes in CYP2C9, CYP2C19, CYP3A, CYP1A2, N-acetyltransferase-2 (NAT-2), and xanthine oxidase (XO) activities were evaluated using warfarin (WARF) + vitamin K, omeprazole (OMP), intravenous (IV) and oral (PO) midazolam (MDZ), and caffeine (CAF).

DESIGN

: Open-label, multiple-dose, pharmacokinetic study in healthy volunteers.

METHODS

Subjects (n = 14) simultaneously received PO WARF 10 mg, vitamin K 10 mg, OMP 40 mg, CAF 2 mg/kg, and IV MDZ 0.025 mg/kg on days (D) 1 and 14, and PO MDZ 5 mg on D2 and D15. LPV/r (400/100 mg twice daily) was administered on D4-17. CYP2C9 and CYP2C19 activities were quantified by S-WARF AUC0-inf and OMP/5-hydroxy OMP ratio, respectively. CYP1A2, NAT-2, and XO activities were quantified by urinary CAF metabolite ratios. Hepatic and intestinal + hepatic CYP3A activities were quantified by IV (CL) and PO (CL/F) MDZ clearance, respectively.

RESULTS

After LPV/r therapy, CYP2C9, CYP2C19, and CYP1A2 activity increased by 29%, 100%, and 43% (P = 0.001, 0.046, and 0.001), respectively. No changes were seen in NAT-2 or XO activity. Hepatic and intestinal + hepatic CYP3A activity decreased by 77% (P < 0.001) and 92% (P = 0.001), respectively.

CONCLUSION

LPV/r therapy results in modest induction of CYP1A2 and CYP2C9 and potent induction of CYP2C19 activity. Increasing doses of concomitant medications metabolized by these enzymes may be necessary. LPV/r inhibited intestinal CYP3A to a greater extent than hepatic CYP3A activity. Doses of concomitant CYP3A substrates should be reduced when combined with LPV/r, although intravenously administered compounds may require less of a relative dose reduction than orally administered compounds.

Determination of the novel non-peptidic HIV-protease inhibitor tipranavir by HPLC–UV after solid-phase extraction

An HPLC method previously described for the assay of amprenavir (APV), ritonavir (RTV), indinavir (IDV), saquinavir (SQV), nelfinavir (NFV), lopinavir (LPV), atazanavir (ATV), nevirapine (NVP) and efavirenz (EFV) can be also conveniently applied, with minor gradient program adjustment, for the determination of the novel non-peptidic HIV protease inhibitor tipranavir (TPV) in human plasma, by off-line solid-phase extraction (SPE) followed by HPLC coupled with UV-diode array detection (DAD). After viral inactivation by heat, the plasma is diluted with phosphate buffer (pH 7), and subjected to a SPE on a C18 cartridge. Matrix components are eliminated with a solution of 0.1% H3PO4 solution neutralised to pH 7, and TPV is eluted with MeOH. The resulting eluate is evaporated and reconstituted in 100 microl MeOH/H2O 50/50. A 40 microl volume is injected onto a Nucleosil C18 AB column and TPV is analysed by UV detection at 201 nm using a gradient elution program constituted of MeCN and phosphate buffer adjusted to pH 5.12 and containing 0.02% sodium heptanesulfonate. The calibration curves are linear up to 75 microg/ml, with a lower limit of quantification of 0.125 microg/ml. The mean absolute recovery of TPV is 77.1+/-4.0%. The method is precise with mean inter-day coefficient of variations (CVs) within 2.2-3.4%, and accurate (range of inter-day deviations from 0.7 to 1.2%). The method has been validated and is currently applied to the monitoring of TPV plasma levels in HIV patients.

Simultaneous determination of 16 anti-HIV drugs in human plasma by high-performance liquid chromatography

Therapeutic drug monitoring (TDM) is pivotal to improve the management of HIV infection. Here, a HPLC-UV method has been developed to quantify simultaneously seven HIV protease inhibitors (amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir; PIs), seven nucleoside reverse transcriptase inhibitors (abacavir, didanosine, emtricitabine, lamivudine, stavudine, zalcitabine, and zidovudine; NRTIs), and two non-nucleoside reverse transcriptase inhibitors (efavirenz and nevirapine; NNRTIs) in human plasma. The volume of the plasma sample was 600 microL. This method involved automated solid-phase extraction with Oasis HLB Cartridge 1 cc (divinylbenzene and N-vinylpyrrolidone) and evaporation in a water bath under nitrogen stream. The extracted samples were reconstituted with 100 microL methanol. Twenty microliters of these samples were injected into a HPLC-UV system, the analytes were eluted on an analytical C(18) Symmetry column (250 mm x 4.6mm I.D.) with a particle size of 5 microm. The mobile phase (0.01 M KH(2)PO(4) and acetonitrile) was delivered at 1.0 mL/min with linear gradient elution. The total run time for a single analysis was 35 min, the anti-HIV drugs were detected by UV at 240 and 260 nm. The calibration curves were linear up to 10 microg/mL. The absolute recovery ranged between 88 and 120%. The in vitro stability of anti-HIV drugs (0.005-10 microg/mL) in plasma has been studied at 24.0 degrees C. On these bases, a two to four analyte method has been tailored to the individual needs of the HIV-infected patient. The HPLC-UV method here reported has been validated and is currently applied to monitor PIs, NRTIs, and NNRTIs in plasma of HIV-infected patients. It allows to monitor the largest number of anti-HIV drugs simultaneously, appearing useful in a routine laboratory, and represents an essential step to elucidate the utility of a formal therapeutic drug monitoring for the optimal follow-up of HIV-infected patients.

Determination of antiretroviral agents in human serum by capillary electrophoresis

In this work, a simple and rapid electrokinetic chromatography method for the simultaneous separation of different protease inhibitors (indinavir, ritonavir, saquinavir, nelfinavir), nucleoside reverse transcriptase inhibitors (stavudine, zidovudine, didanosine) and non-nucleoside reverse transcriptase inhibitors (nevirapine, efavirenz) was developed. The analyses were performed in a 75 microm i.d. uncoated fused-silica capillary with 48.5 cm length (effective length of 40 cm) using a running buffer consisting of 20 mmol L(-1) sodium dodecyl sulfate, 10 mmol L(-1) sodium tetraborate, 30% acetonitrile and 5% ethanol. Samples were injected hydrodynamically by applying 50 mbar pressure during 6 s. All analytes were separated within 10 min with a voltage of 20 kV. The proposed method was validated for zidovudine, didanosine and efavirenz in human serum. Serum samples were prepared using a solid-phase extraction procedure (Waters Oasis HLB cartridges). For quantitative purposes, stavudine was chosen as the internal standard (IS). Method validation parameters were determined revealing good migration time repeatability (<0.7% RSD) and peak area repeatability (<1.2% RSD). Intra- and inter-day precisions were less than 1.7% and 4.4% RSD, respectively. Matrix matching analytical curves for each drug were linear in the 1.0-20.0 microg mL(-1) interval (r > 0.998). Limits of detection (LOD) were in range of 0.3-0.5 microg mL(-1). The extraction recoveries were higher than 90% with exception of efavirenz, which was 77.4%. Based on the performance characteristics, the proposed method was found suitable for the determination of zidovudine, didanosine and efavirenz in serum samples.

Determination of Nevirapine and Efavirenz in Plasma Using GC/MS in Selected Ion Monitoring Mode

An accurate, selective, and sensitive method for the determination of the nonnucleoside reverse transcriptase inhibitors (NNRTIs) nevirapine (nvp) and efavirenz (efv) in human plasma using gas chromatography-mass spectroscopy in selected ion monitoring mode (GC/MS-SIM) was developed. Solid-phase extraction (SPE) gave extraction yields near 100% for both nvp and efv, and calibration curves were linear over the therapeutic concentration ranges. Variation of intraday and interday precision was below 5%. Intraday and interday inaccuracies varied between 0.6% and 10.4%. The lower limits of detection using a 200-microL plasma sample were 27 ng/mL for nvp and 26 ng/mL for efv, and the lower limits of quantification were 54 ng/mL and 72 ng/mL, respectively. The method was applied to the determination of nvp and efv in plasma specimens of 73 patients in HIV stage III or IV and on antiretroviral treatment in Kigali, Rwanda.

Simple and Simultaneous Determination of the HIV-Protease Inhibitors Amprenavir, Atazanavir, Indinavir, Lopinavir, Nelfinavir, Ritonavir and Saquinavir Plus M8 Nelfinavir Metabolite and the Nonnucleoside Reverse Transcriptase Inhibitors Efavirenz and Nevirapine in Human Plasma by Reversed-Phase Liquid Chromatography

Several studies suggest that therapeutic drug monitoring of protease inhibitors and nonnucleoside reverse transcriptase inhibitors may contribute to the clinical outcome of HIV-infected patients. Because of the growing number of antiretroviral drugs and of drug combinations than can be administered to these patients, an accurate high-performance liquid chromatographic (HPLC) method allowing the simultaneous determination of these drugs may be useful. To date, the authors present the first simultaneous HPLC determination of the new protease inhibitor atazanavir with all the others currently in use (M8 nelfinavir metabolite included) and the 2 widely used nonnucleoside reverse transcriptase inhibitors efavirenz and nevirapine. This simple HPLC method allows the analysis all these drugs at a single ultraviolet wavelength following a 1-step liquid-liquid extraction procedure. A 500-muL plasma sample was spiked with internal standard and subjected to liquid-liquid extraction using by diethyl ether at pH 10. HPLC was performed using a Symmetry Shield RP18 and gradient elution. All the drugs of interest and internal standard were detected with ultraviolet detection at 210 nm. Calibration curves were linear in the range 50-10,000 ng/mL. The observed concentrations of the quality controls at plasma concentrations ranging from 50 to 5000 ng/mL for these drugs showed that the overall accuracy varied from 92% to 104% and 92% to 106% for intraday and day-to-day analysis, respectively. No metabolites of the assayed compounds or other drugs commonly coadministered to HIV-positive patients were found to coelute with the drugs of interest or with the internal standard. This assay was developed for the purpose of therapeutic monitoring (TDM) in HIV-infected patients.

Simultaneous determination of six HIV protease inhibitors (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir), the active metabolite of nelfinavir (M8) and non-nucleoside reverse transcriptase inhibitor (efavirenz) in human plasma by high-performance liquid chromatography

We report the development of a simple, economical and reliable chromatographic method for the simultaneous determination of six HIV protease inhibitors (PIs; amprenavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir), the active metabolite of nelfinavir (M8) and the non-nucleoside reverse transcriptase inhibitor (NNRTI; efavirenz) in human plasma. After extraction from plasma with an ethyl acetate-acetonitrile mixture, the analytes were separated on a phenyl column with a gradient of acetonitrile and phosphate solutions, and detected at three ultraviolet wavelengths. Calibration curves were linear over the range 0.025-15 microg/mL for saquinavir and 0.05-15 microg/mL for the other analytes. The accuracies ranged from -6.9% to +7.6%, and the intra-assay and inter-assay precisions were <9.2 and <11.8%, respectively. Our method, covering most of the PIs and NNRTIs currently used, facilitates ready therapeutic drug monitoring in hospital laboratories.