Determination of total and unbound concentrations of lopinavir in plasma using liquid chromatography-tandem mass spectrometry and ultrafiltration methods

A Sequential Ultrafiltration Method to Enhance the Accuracy and Throughput in Plasma Protein Binding Tests

Objectives: Ultrafiltration (UF) is widely accepted as a method for assessing the plasma protein binding (PPB) of drugs. However, it is vulnerable to non-specific binding (NSB) to the device, which can result in inaccuracies. This study presents a straightforward, high-throughput modified UF method aimed at minimizing bias due to NSB. Methods: The modified UF method, sequential UF, features the addition of a 2 min pre-UF phase designed to saturate the NSB in the device, followed by the main 20 min UF procedure, compared to the conventional UF method. To evaluate the feasibility of this sequential UF method, we measured the PPB of nine compounds using sequential UF and compared these results to those obtained with the conventional mass balance UF method, recognized as a standard for NSB correction. Results: The PPB values determined through sequential UF were generally consistent with those derived from the mass balance UF method. The fold differences ranged from 97.9% to 113.8%, with an average of 103.5%. No significant differences were observed between the two methods for all compounds, with the exception of quercetin, which showed an unusually high PPB. Conclusions: Sequential UF was effective in correcting NSB to the device while providing advantages in terms of simplicity and efficiency.

Comparative study of two MIP-based electrochemical sensors for selective detection and quantification of the antiretroviral drug lopinavir in human serum

Thermal polymerization (TP) and electropolymerization (EP) are the two methods used in this study to explore the molecular imprinting process. To detect the antiviral medication lopinavir (LPV), an inhibitor of enzyme HIV-1 protease that is co-formulated with ritonavir (RTV) to extend its half-life in the body, with greater precision, these methods were merged with an electrochemical sensor. The sensors were created on glassy carbon electrodes (GCE) based on molecularly imprinted polymers (MIP) using TP with methacrylic acid (MAA) functional monomer and EP with p-aminobenzoic acid (PABA) functional monomer. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and electrochemical methods were utilized to examine the technical features of the suggested sensors. For both approaches, the necessary optimization investigations were carried out. Different LPV concentrations, ranging from 1.0 pM to 17.5 pM in drug solution and commercial human serum samples, were used to validate the analytical efficiency of the two sensors and compare their electroanalytical behaviour. For TP-LPV@MIP/GCE and EP-LPV@MIP/GCE, the corresponding limit of detection (LOD) was 2.68 × 10-13 M (0.169 pg mL-1) and 1.79 × 10-13 M (0.113 pg mL-1) in standard solutions, and 2.87 × 10-13 M (0.180 pg mL-1) and 2.91 × 10-13 M (0.183 pg mL-1) in serum samples. For the measurement of LPV in tablet form and serum samples, the proposed TP-LPV@MIP/GCE and EP-LPV@MIP/GCE sensors provide good recovery, demonstrating 99.85-101.16 % and 100.36-100.97 % recovery, respectively. The imprinting factor was utilized to demonstrate the selectivity of the suggested sensors by utilizing several anti-viral drugs that are structurally comparable to LPV. Additionally, the constructed sensors were examined for the potential impacts of interferences and the stability during the storage.

Impact of Inflammation on Midazolam Metabolism in Severe COVID-19 Patients

Midazolam is a benzodiazepine frequently used for sedation in patients hospitalized in the intensive care unit (ICU) for coronavirus disease 2019 (COVID-19). This drug is primarily metabolized by cytochrome P450 3A (CYP3A) isoenzymes. Several studies have suggested that inflammation, frequently observed in these patients, could modulate CYP3A activity. The objective of this work was to study the impact of inflammation on midazolam pharmacokinetics in patients with COVID-19. Forty-eight patients hospitalized in the ICU for COVID-19 and treated with midazolam administered by continuous infusion were included in this study. Midazolam and α-hydroxymidazolam concentrations were measured and patient data, including the use of CYP3A inhibitors, were collected. Total and unbound concentrations of midazolam and α-hydroxymidazolam were measured in plasma using a validated liquid-chromatography coupled with mass spectrometry method. Inflammatory condition was evaluated by C-reactive protein (CRP) level measurement. Both drug concentrations and CRP measurements were performed on 354 plasma samples. CRP elevation was significantly associated with the α-hydroxymidazolam/midazolam plasma ratio decrease, whether for the unbound fraction or for the total fraction. Conversely, inflammation was not associated with protein binding modifications. Logically, α-hydroxymidazolam/midazolam plasma ratio was significantly reduced when patients were treated with CYP3A inhibitors. In this study, we showed that inflammation probably reduces the metabolism of midazolam by CYP3A. These results suggest that molecules with narrow therapeutic margins and metabolized by CYP3A should be administrated with care in case of massive inflammatory situations.

Combining subsidiary and synchronous approaches for concurrent spectrofluorimetric assurance of lopinavir and ritonavir in tablets utilized in convention for treatment of coronavirus infection (COVID-19) and biological fluids

In this think about, assurance of lopinavir and ritonavir down to organic concentration level has been carried out. The assurance is based on expanding the selectivity of the spectrofluorimetric procedure by combining both subordinate and synchronous spectrofluorimetric approaches, which allow effective estimation of lopinavir at 248.8 nm and ritonavir at 300.1 nm within the nearness of each other at Δλ of 60 nm. Worldwide Conference on Harmonization approval rules were taken after to completely approve the strategy, and linearity was gotten for the two drugs over the extend of 0.4-2.4 µg mL^-1 for Lopinavir and 0.1-0.6 µg mL^-1 for ritonavir. Application of of the strategy was successfully carried out within the commercial tablets with great understanding with the comparison strategies. As the detection limits were down to 0.133 and 0.022 µg mL^-1 and quantitation limits were 0.395 and 0.068 µg mL^-1 for lopinavir and ritonavir, individually; the in vivo assurance of lopinavir and ritonavir in spiked plasma tests was pertinent. The rate recuperations in natural tests were 99.10 ± 0.77 and 99.54 ± 0.60 for lopinavir and ritonavir, individually. Water was utilized as the ideal weakening dissolvable within the proposed strategy which includes an eco-friendly justify.

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.

Neglecting Plasma Protein Binding in COVID-19 Patients Leads to a Wrong Interpretation of Lopinavir Overexposure

Boffito et al. recalled the critical importance to correctly interpret protein binding. Changes of lopinavir pharmacokinetics in coronavirus disease 2019 (COVID‐19) are a perfect illustration. Indeed, several studies described that total lopinavir plasma concentrations were considerably higher in patients with severe COVID‐19 than those reported in patients with HIV. These findings have led to a reduction of the dose of lopinavir in some patients, hypothesizing an inhibitory effect of inflammation on lopinavir metabolism. Unfortunately, changes in plasma protein binding were never investigated. We performed a retrospective cohort study. Data were collected from the medical records of patients hospitalized for COVID‐19 treated with lopinavir/ritonavir in intensive care units or infectious disease departments of Toulouse University Hospital (France). Total and unbound concentrations of lopinavir, C reactive protein, albumin, and alpha‐1‐acid glycoprotein (AAG) levels were measured during routine care on the same samples. In patients with COVID‐19, increased total lopinavir concentration is the result of an increased AAG‐bound lopinavir concentration, whereas the unbound concentration remains constant, and insufficient to reduce the severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2) viral load. Although international guidelines have recently recommended against using lopinavir/ritonavir to treat severe COVID‐19, the description of lopinavir pharmacokinetics changes in COVID‐19 is a textbook case of the high risk of misinterpretation of a total drug exposure when changes in protein binding are not taken into consideration.

Ultrafiltration Method for Plasma Protein Binding Studies and Its Limitations

Plasma protein binding plays a critical role in drug therapy, being a key part in the characterization of any compound. Among other methods, this process is largely studied by ultrafiltration based on its advantages. However, the method also has some limitations that could negatively influence the experimental results. The aim of this study was to underline key aspects regarding the limitations of the ultrafiltration method, and the potential ways to overcome them. The main limitations are given by the non-specific binding of the substances, the effect of the volume ratio obtained, and the need of a rigorous control of the experimental conditions, especially pH and temperature. This review presents a variety of methods that can hypothetically reduce the limitations, and concludes that ultrafiltration remains a reliable method for the study of protein binding. However, the methodology of the study should be carefully chosen.

Pretreatment and non-specific binding in ultrafiltration device: Impact on protease inhibitor quantification

INTRODUCTION

Ultrafiltration (UF) is used to separate unbound drugs; however, non-specific binding (NSB) may be a limiting factor of this technique. Pretreatment of UF devices has been suggested to reduce NSB. Therefore, the pretreatment methodologies for UF devices were evaluated in order to test their effectiveness in reducing NSB of protease inhibitors (PIs).

METHODOLOGY

Two PIs (lopinavir-LPV and ritonavir-RTV) were tested. UF devices were pretreated with ultrapure water, Tween-20 or Tween-80. To evaluate the NSB, after UF devices being pretreated, ultrafiltrate solutions containing the analytes at two concentrations (low and high) were used. Samples were quantified by LC-MS/MS.

RESULTS

UF devices pretreated with Tween-5% had the lowest NSB for both analytes. NSB values varied between 7 and 11% at low concentration 16-34% at high LPV concentration, respectively. For RTV, NSB was approximately 6% for low concentration and 18% for high concentration. Failure to completely remove Tween in UF devices could results in an overestimation of NSB.

CONCLUSION

Pretreatment of UF device with Tween and subsequent removal proved to be effective in reducing NSB of PI.

Using dried blood spots to facilitate therapeutic drug monitoring of antiretroviral drugs in resource-poor regions

Objectives

We evaluated whether dried blood spots (DBS) are suitable to monitor combined ART when samples are collected in rural Tanzania and transported over a long distance to a specialized bioanalytical laboratory.

Methods

Plasma and DBS samples were collected in Tanzania from study patients treated with nevirapine, efavirenz or lopinavir. In addition, plasma, whole blood and DBS samples were obtained from a cohort of HIV patients at the site of the bioanalytical laboratory in Switzerland. DBS samples were analysed using a fully automated LC-MS/MS method.

Results

Comparison of DBS versus plasma concentrations of samples obtained from the bridging study in Switzerland indicated an acceptable bias only for nevirapine (18.4%), whereas for efavirenz and lopinavir a pronounced difference of -47.4% and -48.1% was found, respectively. Adjusting the DBS concentrations by the haematocrit and the fraction of drug bound to plasma proteins removed this bias [efavirenz +9.4% (-6.9% to +25.7%), lopinavir +2.2% (-20.0% to +24.2%)]. Storage and transportation of samples from Tanzania to Switzerland did not affect the good agreement between plasma and DBS for nevirapine [-2.9% (-34.7% to +29.0%)] and efavirenz [-9.6% (-42.9% to +23.8%)]. For lopinavir, however, adjusted DBS concentrations remained considerably below [-32.8% (-70.4% to +4.8%)] corresponding plasma concentrations due to decay of lopinavir in DBS obtained under field conditions.

Conclusions

Our field study shows that the DBS technique is a suitable tool for therapeutic drug monitoring in resource-poor regions; however, sample stability remains an issue for certain analytes and therefore needs special consideration.

Are Prophylactic and Therapeutic Target Concentrations Different?: the Case of Lopinavir-Ritonavir or Lamivudine Administered to Infants for Prevention of Mother-to-Child HIV-1 Transmission during Breastfeeding

The ANRS 12174 trial assessed the efficacy and tolerance of lopinavir (LPV)-ritonavir (LPV/r) prophylaxis versus those of lamivudine (3TC) prophylaxis administered to breastfed infants whose HIV-infected mothers were not on antiretroviral therapy. In this substudy, we assessed LPV/r and 3TC pharmacokinetics to evaluate the percentage of infants with therapeutic plasma concentrations and to discuss these data in the context of a prophylactic treatment. Infants from the South African trial site underwent blood sampling for pharmacokinetic study at weeks 6, 26, and 38 of life. We applied a Bayesian approach to derive the 3TC and LPV pharmacokinetic parameters on the basis of previously published pharmacokinetic models for HIV-infected children. We analyzed 114 LPV and 180 3TC plasma concentrations from 69 infants and 92 infants, respectively. A total of 30 LPV and 20 3TC observations were considered missing doses and discarded from the Bayesian analysis. The overall population analysis showed that 30 to 40% of the infants did not reach therapeutic targets, regardless of treatment group. The median LPV trough concentrations at weeks 6, 26, and 38 were 2.8 mg/liter (interquartile range [IQR], 1.7 to 4.4 mg/liter), 5.6 mg/liter (IQR, 3.2 to 7.7 mg/liter), and 3.4 mg/liter (IQR, 2.3 to 7.3 mg/liter), respectively. The median 3TC area under the curve from 0 to 12 h after the last drug intake were 5.6 mg · h/liter (IQR, 4.1 to 7.8 mg · h/liter), 5.9 mg · h/liter (IQR, 5.1 to 7.5 mg · h/liter), and 7.3 mg · h/liter (IQR, 4.9 to 8.5 mg · h/liter) at weeks 6, 26, and 38, respectively. Use of the therapeutic doses recommended by the WHO would have resulted in a higher proportion of infants achieving the targets. However, no HIV-1 infection was reported among these infants. These results suggest that the prophylactic targets for both 3TC and LPV may be lower than the therapeutic ones. For treatment, the WHO dosing guidelines should be suitable to maintain values above the therapeutic pharmacokinetic targets in most infants. (This study has been registered at ClinicalTrials.gov under identifier NCT00640263.).

Pharmaceutical applications of affinity-ultrafiltration mass spectrometry: Recent advances and future prospects

The immunoaffinity of protein with ligand is broadly involved in many bioanalytical methods. Affinity-ultrafiltration mass spectrometry (AUF-MS), a platform based on interaction of protein-ligand affinity, has been developed to fish out interesting molecules from complex matrixes. Here we reviewed the basics of AUF-MS and its recent applications to pharmaceutical field, i.e. target-oriented discovery of lead compounds from combinatorial libraries and natural product extracts, and determination of free drug concentration in biosamples. Selected practical examples were highlighted to illustrate the advances of AUF-MS in pharmaceutical fields. The future prospects were also presented.

Population approach to analyze the pharmacokinetics of free and total lopinavir in HIV-infected pregnant women and consequences for dose adjustment

The aims of this study were to describe the unbound and total lopinavir (LPV) pharmacokinetics in pregnant women in order to evaluate if a dosing adjustment is necessary during pregnancy. Lopinavir placental transfer is described, and several genetic covariates were tested to explain its variability. A total of 400 maternal, 79 cord blood, and 48 amniotic fluid samples were collected from 208 women for LPV concentration determinations and pharmacokinetics analysis. Among the maternal LPV concentrations, 79 samples were also used to measure the unbound LPV concentrations. Population pharmacokinetics models were developed by using NONMEM software. Two models were developed to describe (i) unbound and total LPV pharmacokinetics and (ii) LPV placental transfer. The pharmacokinetics was best described by a one-compartment model with first-order absorption and elimination. A pregnancy effect was found on maternal clearance (39% increase), whereas the treatment group (monotherapy versus triple therapy) or the genetic polymorphisms did not explain the pharmacokinetics or placental transfer of LPV. Efficient unbound LPV concentrations in nonpregnant women were similar to those measured during the third trimester of pregnancy. Our study showed a 39% increase of maternal total LPV clearance during pregnancy, whereas unbound LPV concentrations were similar to those simulated in nonpregnant women. The genetic polymorphisms selected did not influence the LPV pharmacokinetics or placental transfer. Thus, we suggest that the LPV dosage should not be increased during pregnancy.