Determination of atazanavir and other antiretroviral drugs (indinavir, amprenavir, nelfinavir and its active metabolite M8, saquinavir, ritonavir, lopinavir, nevirapine and efavirenz) plasma levels by high performance liquid chromatography with UV detection

Nose to brain delivery of nanosuspensions with first line antiviral agents is alternative treatment option to Neuro-AIDS treatment

Intranasal drug delivery is one of the uprising areas of the research in targeting drug to the brain. Nose to brain drug delivery follows the olfactory pathway and purportedly known to be more efficient to deliver neuro-therapeutics to the brain by circumventing the BBB and thereby increasing bioavailability of drugs in the brain. The advantage of this method is non-invasiveness, rapid onset of action and helps to achieve site specific delivery. In this research work nanosuspension were prepared using combination of antiretroviral agents for Neuro-AIDS treatment. Nanosuspensions were prepared by high-speed homogenization, wet milling and high-pressure homogenization techniques. Formulations were analysed by SEM, FTIR, and DSC. Morphology and stability analysis was done by analysing zeta potential, particle size, and PDI. Ex-vivo diffusion study and histopathological analysis was performed using goat nasal mucosa. High pressure homogenization was found to be best technique for formulation of nanosuspension. Antiviral drugs could be delivered successfully by optimizing nasal dosage form.

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.

Multiresponse Optimization of HPLC Method: Simultaneous Estimation of Protease Inhibitors and NNRTI in Human Plasma

Multiresponse optimization approach to develop a simple isocratic, highly sensitive and accurate HPLC method for the simultaneous determination of Efavirenz, Atazanavir, Lopinavir and Ritonavir in human blood plasma along with carvedilol as an internal standard. Optimized the factors (ACN, buffer concentration and flow rate) effecting and interacting with the responses (k1, Rs2,1, Rs3,2 and tR5) applying Central Composite Design a chemometric tool. All the mathematical models as well as response surfaces were defined and derived for the separation using this strategy. Chromatography was performed on Thermo Hypersil C18 column using mobile phase comprising of ACN: 10 mM KH2PO4 (51.2:48.8) with 1 mL min-1 flow rate and detection wavelength was fixed at 210 nm. The analysis time was within 9 min. The method developed was validated by following "Bioanalytical method validation" [USFDA-CDER, 2001]. The developed method can be applied for bioavailability and pharmacokinetic studies.

Lopinavir/Ritonavir: A Review of Analytical Methodologies for the Drug Substances, Pharmaceutical Formulations and Biological Matrices

Lopinavir/ritonavir is a potent coformulation of protease inhibitors used against HIV infection. Lopinavir is the main responsible for viral load suppression, whereas ritonavir is a pharmacokinetic enhancer. Both of them have recently gained relevance as candidate drugs against severe coronavirus disease (COVID-19). However, significant beneficial effects were not observed in randomized clinical trials. This review summarizes the main physical-chemical, pharmacodynamic, and pharmacokinetic properties of ritonavir and lopinavir, along with the analytical methodologies applied for biological matrices, pharmaceutical formulations, and stability studies. The work also aimed to provide a comprehensive impurity profile for the combined formulation. Several analytical methods in four different pharmacopeias and 37 articles in literature were evaluated and summarized. Chromatographic methods for these drugs frequently use C8 or C18 stationary phases with acetonitrile and phosphate buffer (with ultraviolet detection) or acetate buffer (with tandem mass spectrometry detection) as the mobile phase. Official compendia methods show disadvantages as extended total run time and complex mobile phases. HPLC tandem-mass spectrometry provided high sensitivity in methodologies applied for human plasma and serum samples, supporting the therapeutic drug monitoring in HIV patients. Ritonavir and lopinavir major degradation products arise in alkaline and acidic environments, respectively. Other non-chromatographic methods were also summarized. Establishing the impurity profile for the combined formulation is challenging due to a large number of impurities reported. Easier and faster analytical methods for impurity assessment are still needed.

Electrochemical, spectroscopic, and molecular docking studies of the interaction between the anti-retroviral drug indinavir and dsDNA

In this study, an electrochemical DNA biosensor was developed using a straightforward methodology to investigate the interaction of indinavir with calf thymus double-stranded deoxyribonucleic acid (ct-dsDNA) for the first time. The decrease in the oxidation signals of deoxyguanosine (dGuo) and deoxyadenosine (dAdo), measured by differential pulse voltammetry, upon incubation with different concentrations of indinavir can be attributed to the binding mode of indinavir to ct-dsDNA. The currents of the dGuo and dAdo peaks decreased linearly with the concentration of indinavir in the range of 1.0–10.0 μg/mL. The limit of detection and limit of quantification for indinavir were 0.29 and 0.98 μg/mL, respectively, based on the dGuo signal, and 0.23 and 0.78 μg/mL, respectively, based on the dAdo signal. To gain further insights into the interaction mechanism between indinavir and ct-dsDNA, spectroscopic measurements and molecular docking simulations were performed. The binding constant (K_b) between indinavir and ct-dsDNA was calculated to be 1.64 × 10⁸ M⁻¹, based on spectrofluorometric measurements. The obtained results can offer insights into the inhibitory activity of indinavir, which could help to broaden its applications. That is, indinavir can be used to inhibit other mechanisms and/or hallmarks of viral diseases.

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Electrochemical DNA biosensor was fabricated for indinavir-DNA interaction study.

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Indinavir was interacted with ct-dsDNA and made eight hydrogen bonds.

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The Kb was calculated to be 1.64 × 10⁸ M⁻¹ by spectrofluorometry.

Chromatographic methods in HIV medicine: Application to therapeutic drug monitoring

HIV antiretroviral therapy spans several different drug classes, meant to combat various aspects of viral infection and replication. Many authors have argued the benefits of therapeutic drug monitoring (TDM) for the HIV patient including compliance assurance and assessment of appropriate drug concentrations; however, the array of drug chemistries and combinations makes TDM an arduous task. HPLC-UV and LC-MS/MS are both frequent instruments for the quantification of HIV drugs in biological matrices with investigators striving to balance sensitivity and affordability. Plasma, the dominant matrix for these analyses, is prepared using protein precipitation, liquid-liquid extraction or solid-phase extraction depending on the specific complement of analytes. Despite the range of polarities found in drug classes relevant to HIV therapeutics, most chromatographic separations utilize a hydrophobic column (C₁₈ ). Additionally, as the clinically relevant samples for these assays are infected with HIV, along with possible co-infections, another important aspect of sample preparation concerns viral inactivation. Although not routine in clinical practice, many published analytical methods from the previous two decades have demonstrated the ability to conduct TDM in HIV patients receiving various medicinal combinations. This review summarizes the analytical methods relevant to TDM of HIV drugs, while highlighting respective challenges.

Development of an HPLC-UV assay method for the simultaneous quantification of nine antiretroviral agents in the plasma of HIV-infected patients

A new method using high-performance liquid chromatography coupled with ultra violet detection (HPLC–UV) was developed and validated for the simultaneous quantification of atazanavir, dolutegravir, darunavir, efavirenz, etravirine lopinavir, raltegravir, rilpivirine and tipranavir in human plasma. For the first time we reported here the development and validation of an HPLC–UV assay to quantify the frequently administered 9 antiretroviral compounds including dolutegravir and rilpivirine. A simple solid phase extraction procedure was applied to 500 µL aliquots of plasma. The chromatographic separation of the drugs and internal standard (quinoxaline) was achieved with a gradient of acetonitrile and sodium acetate buffer on a C₁₈ reverse-phase analytical column with a 25 min analytical run time. Calibration curves were optimised according to the therapeutic range of drug concentrations in patients, and the coefficient of determination (r²) was higher than 0.99 for all analytes. Mean intraday and interday precisions (RSD) for all compounds were less than 15.0%, and the mean accuracy (% deviation from nominal concentration) was also found to be less than 15.0%. Extraction recovery range was between 80% and 120% for all drugs analysed. The solid phase extraction and HPLC–UV method enable a specific, sensitive, and reliable simultaneous determination of nine antiretroviral agents in plasma. Good extraction efficiency and low limit of HPLC–UV quantification make this method suitable for use in clinical trials and therapeutic drug monitoring.

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.

Validation of simultaneous quantitative method of HIV protease inhibitors atazanavir, darunavir and ritonavir in human plasma by UPLC-MS/MS

OBJECTIVES

HIV protease inhibitors are used in the treatment of patients suffering from AIDS and they act at the final stage of viral replication by interfering with the HIV protease enzyme. The paper describes a selective, sensitive, and robust method for simultaneous determination of three protease inhibitors atazanavir, darunavir and ritonavir in human plasma by ultra performance liquid chromatography-tandem mass spectrometry.

MATERIALS AND METHODS

The sample pretreatment consisted of solid phase extraction of analytes and their deuterated analogs as internal standards from 50 μL human plasma. Chromatographic separation of analytes was performed on Waters Acquity UPLC C18 (50 × 2.1 mm, 1.7 μm) column under gradient conditions using 10 mM ammonium formate, pH 4.0, and acetonitrile as the mobile phase.

RESULTS

The method was established over a concentration range of 5.0-6000 ng/mL for atazanavir, 5.0-5000 ng/mL for darunavir and 1.0-500 ng/mL for ritonavir. Accuracy, precision, matrix effect, recovery, and stability of the analytes were evaluated as per US FDA guidelines.

CONCLUSIONS

The efficiency of sample preparation, short analysis time, and high selectivity permit simultaneous estimation of these inhibitors. The validated method can be useful in determining plasma concentration of these protease inhibitors for therapeutic drug monitoring and in high throughput clinical studies.

Development and validation of a stability-indicating RP-HPLC method for estimation of atazanavir sulfate in bulk

A stability-indicating reverse phase–high performance liquid chromatography (RP–HPLC) method was developed and validated for the determination of atazanavir sulfate in tablet dosage forms using C₁₈ column Phenomenix (250 mm×4.6 mm, 5 μm) with a mobile phase consisting of 900 mL of HPLC grade methanol and 100 mL of water of HPLC grade. The pH was adjusted to 3.55 with acetic acid. The mobile phase was sonicated for 10 min and filtered through a 0.45 μm membrane filter at a flow rate of 0.5 mL/min. The detection was carried out at 249 nm and retention time of atazanavir sulfate was found to be 8.323 min. Linearity was observed from 10 to 90 μg/mL (coefficient of determination R² was 0.999) with equation, y=23.427x+37.732. Atazanavir sulfate was subjected to stress conditions including acidic, alkaline, oxidation, photolysis and thermal degradation, and the results showed that it was more sensitive towards acidic degradation. The method was validated as per ICH guidelines.

Phase I trial of the combination of the Akt inhibitor nelfinavir and chemoradiation for locally advanced rectal cancer

PURPOSE

To investigate the toxicity of nelfinavir, administered during preoperative chemoradiotherapy (CRT) in patients with locally advanced rectal cancer.

MATERIAL AND METHODS

Twelve patients were treated with chemoradiotherapy to 50.4 Gy combined with capecitabine 825 mg/m(2) BID. Three dose levels (DL) of nelfinavir were tested: 750 mg BID (DL1), 1250 mg BID (DL2) and an intermediate level of 1000 mg BID (DL3). Surgery was performed between 8 and 10 weeks after completion of CRT. Primary endpoint was dose-limiting toxicity (DLT), defined as any grade 3 or higher non-hematological or grade 4 or higher hematological toxicity.

RESULTS

Eleven patients could be analyzed: 5 were treated in DL1, 3 in DL2 and 3 in DL3. The first 3 patients in DL1 did not develop a DLT. In DL2 one patient developed gr 3 diarrhea, 1 patient had gr 3 transaminase elevation and 1 patient had a gr 3 cholangitis with unknown cause. An intermediate dose level was tested in DL3. In this group 2 patients developed gr 3 diarrhea and 1 patient gr 3 transaminase elevation and gr 4 post-operative wound complication. Three patients achieved a pathological complete response (pCR).

CONCLUSIONS

Nelfinavir 750 mg BID was defined as the recommended phase II dose in combination with capecitabine and 50.4 Gy pre-operative radiotherapy in rectal cancer. First tumor response evaluations are promising, but a further phase II study is needed to get more information about efficacy of this treatment regimen.

The role of therapeutic drug monitoring in the management of patients with human immunodeficiency virus infection

Therapeutic drug monitoring (TDM) is a well-established method to optimize dosing regimens in individual patients for drugs that are characterized by a narrow therapeutic range and large interindividual pharmacokinetic variability. For some antiretroviral drugs, mainly nonnucleoside reverse transcriptase inhibitors and protease inhibitors, TDM has been proposed as a means to improve the response in human immunodeficiency virus-infected patients. In contrast, nucleoside reverse transcriptase inhibitors do not show a predictable plasma concentration-response (toxicity, efficacy) relationship, and intracellular analyses are expensive. Therefore, TDM is generally not recommended for this class of drugs. TDM has been successfully applied in the clinical practice for certain antiretroviral drugs, but there are ongoing research efforts on the use and refinement of TDM for human immunodeficiency virus treatment, and convincing data from randomized trials are still needed. The best pharmacokinetic measures of drug exposure such as trough and peak concentrations or concentration ratios have not been unambiguously established.

Quantification of 8 HIV-Protease Inhibitors and 2 Nonnucleoside Reverse Transcriptase Inhibitors by Ultra-Performance Liquid Chromatography with Diode Array Detection

Background: Most HPLC-UV methods for therapeutic drug monitoring of anti-HIV drugs have long run times, which reduce their applicability for high-throughput analysis. We developed an ultra-performance liquid chromatography (UPLC)–diode array detection method for the simultaneous quantification of the HIV-protease inhibitors (PIs) amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, and tipranavir (TPV), and the nonnucleoside reverse transcriptase inhibitors (NNRTIs) efavirenz and nevirapine.

Methods: Solid-phase extraction of 1 mL plasma was performed with Waters HLB cartridges. After 3 wash steps, we eluted the drugs with methanol, evaporated the alcohol, and reconstituted the residue with 50 μL methanol. We injected a 4-μL volume into the UPLC system (Waters ACQUITY UPLC BEH C8 column maintained at 60 °C) and used a linear gradient of 50 mmol/L ammonium acetate and 50 mmol/L formic acid in water versus acetonitrile to achieve chromatographic separation of the drugs and internal standard (A-86093). Three wavelengths (215, 240, and 260 nm) were monitored.

Results: All drugs were eluted within 15 min. Calibration curves with concentrations of 0.025–10 mg/L (1.875–75 mg/L for TPV) showed coefficients of determination (r2) between 0.993 and 0.999. The lower limits of quantification were well below the trough concentrations reported in the literature. Inter- and intraassay CVs and the deviations between the nominal and measured concentrations were <15%. The method was validated by successful participation in an international interlaboratory QC program.

Conclusions: This method allows fast and simultaneous quantification of all commercially available PIs and NNRTIs for therapeutic drug monitoring.

Development and evaluation of an immunoassay for the monitoring of the anti-HIV drug amprenavir

An assay for routine therapeutic drug monitoring of anti-HIV HAART drugs in clinical use is highly desirable, in order to rapidly measure the pharmacokinetic parameters on single patients. We have started a project to develop a panel of enzyme-linked immunosorbent assays (ELISA) for the whole set of HAART drugs, and the development, performance and evaluation of the assay for amprenavir is described here. A diazo conjugate of amprenavir has been used in order to raise polyclonal anti-amprenavir antibodies in rabbits. Antisera have been used to set up a quantitative and rapid competitive assay. Plasma samples are simply diluted in the assay buffer after thermal inactivation, before running the assay. The assay allows the detection of amprenavir in the quantification range 400-5000 ng/ml, in a diluted plasma sample. The assay has been compared with an HPLC reference technique, on 27 samples from treated patients. Within the quantification range, the ELISA data are well correlated with the HPLC results by a regression line close to the identity, and a Bland-Altman analysis shows the agreement between the two methods.

Electrospray tandem mass spectroscopic characterisation of 18 antiretroviral drugs and simultaneous quantification of 12 antiretrovirals in plasma

The determination of antiretroviral drug concentrations in patients treated with highly active antiretroviral therapy (HAART) is an essential part of optimum patient management because of the multitude of pharmacokinetic drug interactions between these drugs and the risk of treatment failure or viral resistance if therapeutic concentrations are not reached. Currently, 21 different antiretrovirals are used in various combinations rendering therapeutic drug monitoring a laborious task. We therefore aimed to simultaneously determine as many antiretrovirals as possible using triple quadrupole mass spectroscopy with electrospray ionisation. For this purpose, spectra and fragmentation patterns of the protease inhibitors amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir, the non-nucleoside reverse transcriptase inhibitors delavirdine, efavirenz, and nevirapine, the nucleoside reverse transcription inhibitors abacavir, didanosine, emtricitabine, lamivudine, stavudine, zalcitabine, and zidovudine, and the nucleotide reverse transcriptase inhibitor tenofovir were evaluated. A bioanalytical method to determine all protease and non-nucleoside reverse transcriptase inhibitors, and zalcitabine and zidovudine concentrations in biological matrices was developed. Samples were prepared by protein precipitation with methanol after addition of three different internal standards. Antiretrovirals were separated by high-performance liquid chromatography on a Nucleosil C18-100 Nautilus column using a gradient of 20 mM ammonium acetate including 0.1% aqueous acetic acid and acetonitrile and detected by electrospray ionisation/tandem mass spectrometry in the negative (efavirenz, stavudine, zidovudine) or positive ionisation mode (all other compounds). The bioanalytical method was successfully validated according to FDA guidelines and applied to plasma and cerebrospinal fluid samples of patients treated for acquired immunodeficiency syndrome (AIDS).

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.

Quantitative immunoassay to measure plasma and intracellular atazanavir levels: analysis of drug accumulation in cultured T cells

We have developed an enzyme immunoassay to measure atazanavir (ATV) levels in plasma and cells. Anti-ATV polyclonal antibodies were raised in rabbits by using a synthetic ATV derivative coupled to bovine serum albumin as the immunogen, and the enzyme tracer was prepared by chemically coupling the ATV derivative with acetylcholinesterase. These reagents were used to develop a sensitive competitive enzyme immunoassay performed in microtitration plates, and the lowest limit of quantification was 150 pg/ml, which is about 10 times more sensitive than previously published techniques. The plasma assay was performed, after a simple methanol extraction, with a minimum of 30 microl of plasma. This assay showed good precision and efficiency, since the rates of recovery from human plasma and cell extracts spiked with ATV ranged form 93 to 113%, with coefficients of variation of less than 10%. ATV concentrations were measured in peripheral blood mononuclear cells incubated with various ATV concentrations and in CEM cells in the absence or presence of antiretroviral drugs and drug transporter inhibitors. The results indicated a dose-dependent uptake (intracellular concentration/extracellular concentration ratio range, 0.04 to 19). A significant increase in the accumulation of ATV was noticed in the presence of P-glycoprotein and MRP1 inhibitors (dipyridamole, inter alia). Interestingly, efavirenz significantly increased the baseline accumulation of ATV, whereas nevirapine induced a marked reduction. This new enzyme immunoassay for measuring plasma and intracellular ATV levels was fully validated and provides an inexpensive and useful tool for routine therapeutic drug monitoring. Moreover, in vitro results suggested the implication of drug transporters and interactions with other antiviral drugs that should be further explored in human immunodeficiency virus-infected patients.

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).

Simple determination of the HIV protease inhibitor atazanavir in human plasma by high-performance liquid chromatography with UV detection

A simple high-performance liquid chromatography method for the determination of the human immunodeficiency virus protease inhibitor atazanavir in human plasma samples was developed and validated. The method involved a rapid and simple solid-phase extraction of atazanavir using Oasis HLB 1cc cartridges, an isocratic reversed-phase liquid chromatography on an XTerra RP18 (150mmx4.6mm, 3.5microm) column, and ultraviolet detection at 203nm. The mobile phase consisted of phosphate buffer (pH 6, 52.5mM) and acetonitrile (43:57, v/v). Up to 48 samples could be measured in one day since the run-time of one sample was 30min. The assay was linear from 0.04 to 10microg/ml with a lower limit of quantification of 0.04microg/ml. The mean absolute recovery of ATV was 98.1%. The method was precise, with both intra-day and inter-day coefficients of variation < or =3.0%, and accurate (deviations ranged from -3.0% to 4.5% and from -3.6% to 4.7% for intra-day and inter-day analysis, respectively). There was no interference from 35 tested potentially co-administrated drugs. This method provides a simple, sensitive, precise and reproducible assay for the therapeutic drug monitoring of atazanavir in clinical routine of laboratories with standard equipment.

Influence of tenofovir, nevirapine and efavirenz on ritonavir-boosted atazanavir pharmacokinetics in HIV-infected patients

OBJECTIVE

The influence of nevirapine, efavirenz and tenofovir co-administration on ritonavir-boosted atazanavir pharmacokinetics was investigated in HIV (human immunodeficiency virus)-infected patients.

METHODS

A population pharmacokinetic analysis was performed in the context of therapeutic drug monitoring (87 patients, 121 samples).

RESULTS

A significant increase of atazanavir clearance (Cl/F) was found when either tenofovir (group B), efavirenz (group C), or nevirapine (group D) were co administered with atazanavir/ritonavir in comparison with patients treated with atazanavir/ritonavir and nucleoside reverse transcriptase inhibitors (group A): 6.24+/-0.36 l h(-1) (group A) versus 7.42+/-0.25 l h(-1) (group B) versus 9.60+/-0.27 l h(-1) (group C) versus 17.53+/-0.57 l h(-1) (group D) (P<0.001). However, the decrease of the mean trough plasma concentration of atazanavir was significant only in group D: 1.02+/-0.86 mg/l (group A) versus 0.21+/-013 mg/l (group D) (P<0.001).

CONCLUSION

The increase in atazanavir clearance when it is used in combination with nevirapine, efavirenz and/or tenofovir suggests that therapeutic drug monitoring of atazanavir should be performed in such circumstances.

No significant influence of saquinavir hard-gel capsule administration on pharmacokinetics of lopinavir in combination with ritonavir: a population approach

The influence of saquinavir hard-gel capsules on lopinavir pharmacokinetic parameters was investigated using a population approach. Forty-nine patients infected with human immunodeficiency virus type 1 and treated with lopinavir/ritonavir, nucleoside/nucleotide reverse transcriptase inhibitors plus saquinavir (group A), and 118 patients treated with lopinavir/ritonavir plus nucleoside/nucleotide reverse transcriptase inhibitors (group B) were included in the study. No significant relationship was established between the presence or the daily dosage of saquinavir in the treatment and lopinavir population pharmacokinetic parameters. The values (mean+/-standard deviation) of the individual apparent clearance (5.0+/-1.8 vs. 5.0+/-3.2 L/h), volume of distribution (66.6+/-1.6 vs. 66.8+/-1.9 L), absorption rate constant (0.37+/-0.01 vs. 0.37+/-0.03 hours), and trough plasma concentration (5.5+/-2.3 vs. 5.3+/-1.9 mg/L) of lopinavir are not significantly different between groups A and B. This lack of influence of saquinavir on lopinavir pharmacokinetics makes the use of this combination in salvage therapy easier.

Low initial trough plasma concentrations of lopinavir are associated with an impairment of virological response in an unselected cohort of HIV-1-infected patients

OBJECTIVES

The relationship between lopinavir trough plasma concentration at baseline and virological efficacy 3 months after the beginning of the therapy was investigated in an unselected cohort of HIV-1-infected patients

METHODS

According to initial trough lopinavir plasma level, patients were classified into three groups: the subtherapeutic group (<3 mg/L, n=18), the therapeutic group (between 3 and 8 mg/L, n=50) and the toxic group (>8 mg/L, n=16). The virological response after 3 months of lopinavir treatment, defined as a viral load <200 HIV-1 RNA copies/mL, was compared amongst these groups.

RESULTS

The virological response was significantly different (P<0.05) between the subtherapeutic group (22.% of patients with viral load<200 copies/mL) and the other groups (56.0% of patients with a viral load<200 copies/mL in the therapeutic group and 56.2% in the toxic group).

CONCLUSIONS

A lower virological efficacy should be expected for experienced or naive patients with plasma trough lopinavir concentrations<3 mg/L at the beginning of treatment.

Simple and rapid liquid chromatography method for determination of efavirenz in plasma

A simple and rapid high performance liquid chromatographic method for determination of efavirenz in human plasma was developed. The method involved extraction of sample with ethyl acetate and analysis using a reversed-phase C(18) column (150 mm) with UV detection. The assay was linear from 0.0625 to 10.0 microg/ml. The method was specific for efavirenz estimation and the drug was stable in plasma up to one month at -20 degrees C. The average recovery of efavirenz from plasma was 101%. Due to its simplicity, the assay can be used for pharmacokinetic studies and therapeutic drug monitoring of efavirenz.

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.

Pharmacokinetic evidence for the induction of lopinavir metabolism by efavirenz

AIMS

The influence of efavirenz on lopinavir pharmacokinetics was investigated using a population approach.

METHODS

Forty-five HIV patients treated with lopinavir/ritonavir plus efavirenz (A) and 24 patients treated with lopinavir/ritonavir plus nucleoside/nucleotide reverse transcriptase inhibitors (B) were studied.

RESULTS

A relationship (P < 0.01) was established between the elimination rate constant of lopinavir (k(10)) and treatment with efavirenz. Mean k(10) was higher in group A than in group B (0.3838 vs 0.2810 h(-1)) (P < 0.001, 95% confidence interval for difference between means 0.1004, 0.1052).

CONCLUSIONS

These results suggest that lopinavir metabolism is induced by efavirenz.

Determination of atazanavir in human plasma using solid-phase extraction and high-performance liquid chromatography

Atazanavir is a new HIV-1 protease inhibitor. A simple high-performance liquid chromatographic method using UV detection was developed and validated for the analysis of atazanavir in human plasma. The sample clean up was carried out using solid-phase extraction with OASIS MCX cartridge. The chromatographic separation was achieved on a Kromasil C18 (150 mm x 3 mm, 5 microm) column with a mobile phase consisting of acetonitrile and water (38:62 v/v) delivered isocratically. The effluent of the column was monitored at a wavelength of 210 nm. The assay was linear over the concentration range of 0.156 to 10 microg/ml and the limit of quantification was 0.156 microg/ml. The method was also validated with respect to recovery, precision, accuracy and specificity. This method is suitable for therapeutic drug monitoring of atazanavir and can be easily reproduced with standard equipment.

Liquid chromatographic assay for the protease inhibitor atazanavir in plasma

Atazanavir is the most recently introduced protease inhibitor for the suppression of the anti-human immunodeficiency virus. A sensitive and selective reversed-phase liquid chromatographic assay for this drug in human plasma has been developed and validated. Atazanavir was isolated from a 500 microL plasma sample using liquid-liquid extraction with dichloromethane. After evaporation and reconstitution of the extract the sample was analysed using liquid chromatography and ultraviolet detection at 280 nm. In the evaluated concentration range (44-4395 ng/mL atazanavir), intra-day precisions were < or =7% and inter-day precisions were < or =14%. Accuracies between 96 and 106% were found. The lower limit of quantification was 44 ng/mL with an intra-day precision of 7%, an inter-day precision of 14% and an accuracy of 87%. There was no interference from 32 tested potentially co-administrated drugs and metabolites. The usefulness of the assay was demonstrated for samples obtained from an HIV-infected patient treated with atazanavir.