Simultaneous determination of nirmatrelvir and ritonavir in human plasma by LC-MS/MS and its pharmacokinetic application in healthy Chinese subjects

Real-world Plasma Exposure of Nirmatrelvir/Ritonavir in Chinese Hospitalized Patients With COVID-19: A Multicenter Retrospective Study

BACKGROUND

Nirmatrelvir/ritonavir is licensed for the treatment of mild-to-moderate coronavirus disease (COVID-19) in patients at an increased risk of progression to severe disease. However, data on the real-world plasma exposure to nirmatrelvir/ritonavir remain limited, particularly in Chinese patients. This study aimed to assess the nirmatrelvir/ritonavir trough concentration (Ctrough) and identify its critical factors in hospitalized Chinese patients treated with nirmatrelvir/ritonavir 300 mg/100 mg twice daily over a 5-day course.

METHODS

A high-performance liquid chromatography-tandem mass spectrometry assay was developed and validated to measure the nirmatrelvir/ritonavir Ctrough. Correlation analyses were performed to identify the variables influencing nirmatrelvir/ritonavir Ctrough.

RESULTS

Among the 110 patients, 100% had plasma concentrations above the antiviral in vitro 90% effective concentration. The median Ctrough of nirmatrelvir was 4.55 mcg/mL (15.6× 90% effective concentration), ranging from 0.65 to 12.44 mcg/mL. Nirmatrelvir Ctrough in normal and mild renal impairment cohorts were comparable (4.09 ± 1.97 mcg/mL and 4.57 ± 2.21 mcg/mL) but significantly increased in the moderate renal impairment cohort (6.41 ± 2.31 mcg/mL). Sex, age, and obesity were not significantly associated with nirmatrelvir exposure.

CONCLUSIONS

Nirmatrelvir Ctrough was high in Chinese patients with COVID-19, and therapeutic drug monitoring should not be routinely recommended, except in patients with renal impairment.

Simultaneous determination of nirmatrelvir, ritonavir, and beta-D-N4-hydroxycytidine in human plasma and epithelial lining fluid using LC-MS/MS and its clinical application to compare rates of achieving effective concentrations

Currently, the trials found that the clinical efficacy of molnupiravir is lower than ritonavir-boosted nirmatrelvir. An explanation for these different efficacies in clinical treatments is still limited. The analysis method was developed and validated to simultaneously quantify nirmatrelvir, ritonavir, and beta-D-N4-hydroxycytidine (NHC) in human plasma and bronchoalveolar lavage fluid (BALF) by electrospray ionization mass spectrometry. Our method was validated over a linear range of 30-10000 ng/mL for both matrices, with precision and accuracy within 15 % across four concentrations. Recovery rates for both analytes from plasma and BALF were between 90.7-102.2 % and 90.5-107.7 %, respectively. The analytical method was then applied to monitor therapeutic drug concentrations in 59 plasma samples from 23 patients receiving ritonavir-boosted nirmatrelvir or molnupiravir. By setting target plasma concentrations of 292 ng/mL for nirmatrelvir and 1205 ng/mL for NHC, based on in vitro antiviral 90 % virus inhibitory concentrations (EC90), the drug's molecular weight and its binding to human plasma proteins, we observed that ritonavir-boosted nirmatrelvir had substantially greater rates of achieving target plasma concentrations. Additionally, we monitored epithelial lining fluid in 4 BALF samples from 4 patients and observed that NHC exhibited higher permeability in lung tissue (approximately 20 % higher than nirmatrelvir). However, subtherapeutic antiviral concentrations of NHC were also present in epithelial lining fluid. These findings highlight the importance of considering these factors in determining the efficacy of these drugs in treating coronavirus disease 2019 (COVID-19).

Stability indicating RP-HPLC technique for simultaneous estimation of nirmatrelvir and ritonavir in their new copackaged dosage form for COVID-19 treatment

RP-HPLC technique was developed and optimized for simultaneous identification and estimation of nirmatrelvir (NIR) and ritonavir (RIT) in their new copackaged tablet. Stability of nirmatrelvir (NIR) was studied after exposure to different five stress conditions; alkali, acid, heat, photo and oxidation degradation. The chromatographic separation was achieved using VDSpher PUR 100 ODS (4.6-mm x 15-mm), 3.5 μm column and mixture of 0.03 M potassium di-hydrogen phosphate buffer pH 4 and acetonitrile (45:55, v/v) as mobile phase. The column temperature was set at 40 °C, flow rate at 1mL/min and UV detection at 215 nm. The NIR and RIT retention times were 3.94 ± 0.08 min and 9.08 ± 0.1 min, respectively. Linear relationship was established in range of (1.5-105 µg/mL) for NIR and (1-70 µg/mL) for RIT with good reproducibility. The found mean percentage recoveries of nirmatrelvir (NIR) and ritonavir (RIT) were 100.03% and 99.85%, respectively. The developed method shows very good sensitivity as the LOQ and LOD were found to be 3.001 & 0.990 µg/mL, respectively for NIR and 2.765 & 0.912 µg/mL, respectively for RIT. The developed approach was validated concerning to ICH guidelines and applied successfully for the simultaneous estimation of NIR and RIT in their new copackaged dosage from. The results of assay using the proposed approach were compared statistically to the results found by applying the published one with good agreement.

Population pharmacokinetics of nirmatrelvir/ritonavir in critically ill Chinese COVID-19 patients and recommendations for medication use: a two-center retrospective study

BACKGROUND

This study aimed to establish population pharmacokinetics (PPK) models of nirmatrelvir/ritonavir in critically ill Chinese patients with the coronavirus disease 2019 (COVID-19) infection, explore factors affecting the pharmacokinetics (PK) of nirmatrelvir/ritonavir.

METHODS

A total of 285 serum samples and clinical data were collected from 152 patients. The PPK models of nirmatrelvir/ritonavir were analyzed using nonlinear mixed-effect modeling (NONMEM) approach. The optimal dosing regimen for patients with different renal function was determined using Monte Carlo simulations.

RESULTS

The population typical values of apparent clearance (CL/F) and apparent volume of distribution (V/F) of nirmatrelvir were 2.26 L/h and 15.3 L, respectively. Notably, creatinine clearance (CrCL) significantly influenced the PK variation of nirmatrelvir. Monte Carlo simulations suggested that patients with mild-to-moderate renal impairment experienced a 22.0-59.9% increase in the area under the curve (AUC) when they were administered a standard dose of nirmatrelvir compared to those with normal renal function. The AUC in patients with severe renal impairment after administration of 150 mg q12h nirmatrelvir was similar to that in patients with normal renal function after administration of 300 mg q12h nirmatrelvir.

CONCLUSIONS

PPK modeling and simulation provided a reference for the rational clinical application of nirmatrelvir/ritonavir in critically ill Chinese patients.

Analysis of Nirmatrelvir Entry into Pulmonary Lining Fluid in Patients with COVID-19: A Unique Perspective to Explore and Understand the Target Plasma Concentration of 292 ng/mL in Antiviral Activity

BACKGROUND

Currently, the applicant has chosen a target plasma trough concentration for nirmatrelvir, which is adjusted to 292 ng/mL based on the drug's molecular weight (499.54 Daltons), its binding to human plasma proteins (69%), and the in vitro antiviral EC90 value (181 nM). However, the current exposure-effect relationships (ER) analysis of viral load in patients enrolled in the EPIC-HR study has not revealed clinically significant trends in the ER. Given that the lungs are the primary site of COVID-19 infection, we aim to further understand this exposure relationship by exploring and analyzing the penetration characteristics of nirmatrelvir in the lungs.

OBJECTIVES

To explore and understand the target plasma concentration of 292 ng/mL in antiviral activity.

METHODS

We identified all critically ill patients with coronavirus disease 2019 who received nirmatrelvir/ritonavir treatment in the respiratory intensive care unit of Changhai hospital between January 2023 and October 2023. Samples of plasma and bronchoalveolar lavage fluid were obtained at pre-dose trough concentrations after administration of nirmatrelvir (NMV). The relationship between NMV levels in plasma and the epithelial lining fluid (ELF) was assessed by determining concentrations of NMV.

RESULTS

There was a significant relationship between NMV levels in plasma and ELF (ELF = 0.4976*PLASMA- 204; R = 0.96), with a correlation whose slope (0.4976) suggested that the blood-to-ELF ratio of drug penetration was 2:1. A negative value from the equation indicates that NMV requires to reach baseline concentration to penetrate the ELF.

CONCLUSIONS

The relationship between NMV levels in plasma and ELF with low permeability and a negative baseline value suggests that the target plasma concentration of 292 ng/mL is insufficient for antiviral activity. This study provides a unique perspective to explore and understand no clinically meaningful trend of exposure-response relationships in patients enrolled in EPIC-HR.

Identification, characterization, and in silico ADMET prediction of nirmatrelvir and its degradation products using HPLC-PDA and LC-QTOF-MS/MS

RATIONALE

Nirmatrelvir is a protease inhibitor that is essential for virus replication. Nirmatrelvir is indicated for the management of mild to severe cases of COVID-19 in individuals who are 12 years of age or older. Forced degradation studies of nirmatrelvir were carried out on the drug substance in solid and solution forms, subjecting it to various stress conditions according to International Conference on Harmonisation (ICH) Q1A(R2) and Q1B guidelines. The analytical method was validated as per the ICH Q2(R1) guidelines.

METHODS

The drug substance (nirmatrelvir) was subjected to hydrolysis (acidic, alkaline, and neutral), thermal, photolytic, and oxidative stress conditions. Five degradation products (DPs) of nirmatrelvir formed under hydrolytic (acidic and alkaline) and oxidative (2,2-azobisisobutyronitrile) stress conditions. These degradation products were identified and separated using reverse-phase HPLC on a phenomenex kinetex C8 column (250 mm × 4.6 mm × 5 μm) with gradient elution. The mobile phase consisted of 0.1% formic acid and acetonitrile, and detection was carried out at a wavelength of 210 nm.

RESULTS AND CONCLUSIONS

Nirmatrelvir and its five DPs were efficiently separated using reverse phase-HPLC. These five DPs were identified and characterized using LC-electrospray ionization (ESI)-Q-TOF-coupled mass spectrometry analysis in the ESI-positive ionization mode. The formation mechanisms of the DPs and the most probable mass fragmentation pathways for both nirmatrelvir and its DPs were elucidated. The developed method demonstrated selectivity, accuracy, linearity, and reproducibility, making it appropriate for quality control of nirmatrelvir and future research studies. Additionally, the physicochemical and Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET) properties of nirmatrelvir and its DPs were predicted using ADMET predictor software. The toxicity profile revealed that DP2 and DP3 have teratogenic effects while DP1 and DP3 caused phospholipidosis.

Hyphenating sustainability with chemometrics in chromatographic analysis of COVID combo therapy, nirmatrelvir and Molnupiravir, in presence of their overlapping degradation products; blue-green dual evaluation tools

Our manuscript managed to hyphenate the novelty and sustainability in one method. A novel combination of molnupiravir (MNP) and nirmatrelvir (NTV) was found to be a potential symbiotic therapy against SARS-CoV-2. Yet, there is no analytical method published for either determination or stability investigation of this combination simultaneously. So, the proposed HPLC technique focused on determination of MNP and NTV in presence of their degradation products. The sustainability was achieved in our method by using chemometrics tools to quantify NTV in presence of its co-eluted degradation product (NTV-D) without excessive time and solvent usage for separation (run time 5 min.). Moreover, the linearity parameters of both MNP and NTV, including correlation coefficient, LOD and LOQ, have been enhanced significantly after chemometrics treatment through convolution of the resultant derivative curves using trigonometric Fourier function. For example, LOQ of MNP decreased from 3.53 to 0.31 µg/mL and for NTV, LOQ decreased from 4.98 to 2.10 µg/mL after chemometrics treatment. The stability results of the proposed method indicates that no interaction or change in stability behavior of both drugs when co-administered with each other. Thus, this can be used as an empirical basis to initiate clinical trials of this combination for the treatment of COVID-19 patients. Additionally, in order to determine the impact of chemometric methods in minimizing analysis time and reducing solvent, energy, and waste consumption, our chemometric methodology is evaluated in terms of greenness and blueness (dichromic assessment) using AGREE and BAGI, respectively. Besides, the method sustainability using Hexagon was evaluated.

Sustainable and technically smart spectrophotometric determination of PAXLOVID: a comprehensive ecological and analytical performance rating

The Food and Drug Administration (FDA) authorized the administration of ritonavir (RIT)-boosted nirmatrelvir (NMV) on May 25, 2023, for the treatment of mild to moderate COVID-19 in patients who are at high risk of developing severe COVID-19. In accordance with sustainability and environmental friendliness, simple, eco-friendly, and sustainable spectrophotometric methods were established for concurrently estimating RIT and NMV in newly launched copackaged pills. The suggested solutions for resolving the spectral overlap between RIT and NMV involve the following mathematical methods: the first derivative method (1D), second derivative method (2D), and dual-wavelength zero-order method (DWZ). When ethanol was used as a green dilution solvent, the linearity range was adjusted (10-250 µg/mL) for both drugs. The procedures resulted in a high correlation coefficient (not less than 0.9996) and satisfactory levels of detection and quantification. Additionally, method validation was performed in accordance with International Council for Harmonization norms. Moreover, a detailed ecological and sustainability evaluation protocol was established to confirm the greenness and whiteness of the methods. Finally, the proposed method, along with previously reported methods for analysing NMV and RIT, were reviewed analytically and ecologically.

The anti-COVID-19 drug nirmatrelvir crosses the blood‒brain barrier and exhibits herb-drug pharmacokinetic interactions with Scutellaria baicalensis formulations

Aim of the study

Our hypothesis is that nirmatrelvir can penetrate the blood‒brain barrier and reach effective concentrations in the brain. Furthermore, herbal formulations can help maintain nirmatrelvir levels in the body, suggesting potential interactions between these medications.

Materials and methods

To investigate this hypothesis, an animal model combining multisite microdialysis, ultrahigh-performance liquid chromatography and tandem mass spectrometry (UHPLC-MS/MS) methods was developed to monitor nirmatrelvir levels in the blood and brain of rats.

Results

The pharmacokinetic results showed that the area under the curve (AUC) of nirmatrelvir in the blood and brain was 798.3 ± 58.56 and 187.2 ± 23.46 min μg/mL, respectively, after the administration of nirmatrelvir alone (15 mg/kg, iv). When the Scutellaria baicalensis formulations were administered for five consecutive days prior to drug administration, the AUC of nirmatrelvir in the blood increased.

Conclusions

These results provide constructive preclinical information that the concentrations of nirmatrelvir in the blood and brain were greater than the effective concentration (EC90) for more than 6 h, and the Scutellaria baicalensis formulations had synergistic pharmacokinetic effects by increasing the concentration of nirmatrelvir in the blood.

Population pharmacokinetics of nirmatrelvir in Chinese patients with COVID-19: Therapeutic drug monitoring and dosing regimen selection in clinical practice

OBJECTIVES

To establish a population pharmacokinetics (PopPK) model of nirmatrelvir in Chinese COVID-19 patients and provide reference for refining the dosing strategy of nirmatrelvir in patients confirmed to be infected with SARS-CoV-2.

METHODS

A total of 80 blood samples were obtained from 35 mild to moderate COVID-19 patients who were orally administered nirmatrelvir/ritonavir tablets. The PopPK model of nirmatrelvir was developed using a nonlinear mixed effects modelling approach. The stability and prediction of the final model were assessed through a combination of goodness-of-fit and bootstrap method. The exposure of nirmatrelvir across various clinical scenarios was simulated using Monte Carlo simulations.

RESULTS

The pharmacokinetics of nirmatrelvir was well characterised by a one-compartment model with first-order absorption, and with creatinine clearance (Ccr) as the significant covariate. Typical population parameter estimates of apparent clearance and distribution volume for a patient with a Ccr of 95.5 mL·min-1were 3.45 L·h-1 and 48.71 L, respectively. The bootstrap and visual predictive check procedures demonstrated satisfactory predictive performance and robustness of the final model.

CONCLUSION

The final model was capable of offering an early prediction of drug concentration ranges for different nirmatrelvir dosing regimens and optimise the dose regimen of nirmatrelvir in individuals with confirmed SARS-CoV-2 infection.

Population pharmacokinetics and pharmacodynamics of nirmatrelvir in Chinese patients with COVID-19

BACKGROUND

The pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of nirmatrelvir (NMV) are unknown in Chinese patients with COVID-19.

OBJECTIVES

To understand the PK, as well as PK-PD characteristics of NMV for optimizing the dose in Chinese patients with COVID-19.

METHODS

We enrolled 141 participants who received NMV 300 mg/ritonavir (RTV) 100 mg b.i.d. for 5 days. The NMV concentrations were analyzed using 251 blood samples. PK/PD of NMV was investigated in these COVID-19 patients using a nonlinear mixed-effects model.

RESULTS

The patients had a mean age of 82 years (range, 34-97). The absorption rate constant and apparent clearance of NMV in this Chinese cohort were 0.253 h-1 and 6.83 L/h, respectively, similar to Caucasian patients. No covariates affected NMV clearance. Predicted peak (Cmax) and trough concentration (Cmin) under 300 mg NMV/100 mg RTV b.i.d. were 4004 and 1498 ng/mL, respectively. Although higher AUC and Cmin were weakly associated with a slight increase in the number of cycle threshold (CT) of viral genes, no significant correlation was found, indicating a weak relationship between drug exposure and efficacy (CT).

CONCLUSIONS

In all, our findings suggest no ethnic PK differences, a weak and clinically insignificant relationship between drug exposure and efficacy, suitable dosage for Chinese patients (including the elderly) based on PK parameters, and the need for further studies to determine optimal regimens for high-risk patients due to inter-individual variability.

Simultaneous measurement of COVID-19 treatment drugs (nirmatrelvir and ritonavir) in rat plasma by UPLC-MS/MS and its application to a pharmacokinetic study

PAXLOVID™ (Co-packaging of Nirmatrelvir with Ritonavir) has been approved for the treatment of Coronavirus Disease 2019 (COVID-19). The goal of the experiment was to create an accurate and straightforward analytical method using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) to simultaneously quantify nirmatrelvir and ritonavir in rat plasma, and to investigate the pharmacokinetic profiles of these drugs in rats. After protein precipitation using acetonitrile, nirmatrelvir, ritonavir, and the internal standard (IS) lopinavir were separated using ultra performance liquid chromatography (UPLC). This separation was achieved with a mobile phase composed of acetonitrile and an aqueous solution of 0.1% formic acid, using a reversed-phase column with a binary gradient elution. Using multiple reaction monitoring (MRM) technology, the analytes were detected in the positive electrospray ionization mode. Favorable linearity was observed in the calibration range of 2.0-10000 ng/mL for nirmatrelvir and 1.0-5000 ng/mL for ritonavir, respectively, within plasma samples. The lower limits of quantification (LLOQ) attained were 2.0 ng/mL for nirmatrelvir and 1.0 ng/mL for ritonavir, respectively. Both drugs demonstrated inter-day and intra-day precision below 15%, with accuracies ranging from -7.6% to 13.2%. Analytes were extracted with recoveries higher than 90.7% and without significant matrix effects. Likewise, the stability was found to meet the requirements of the analytical method under different conditions. This UPLC-MS/MS method, characterized by enabling accurate and precise quantification of nirmatrelvir and ritonavir in plasma, was effectively utilized for in vivo pharmacokinetic studies in rats.

Development of a novel quality by design-enabled stability-indicating HPLC method and its validation for the quantification of nirmatrelvir in bulk and pharmaceutical dosage forms

A systematic and novel quality by design-enabled, rapid, simple, and economic stability-indicating HPLC method for quantifying nirmatrelvir (NMT) was successfully developed and validated. An analytical target profile (ATP) was established, and critical analytical attributes (CAAs) were allocated to meet the ATP requirements. The method used chromatographic separation using a Purosphere column with a 4.6 mm inner diameter × 250 mm (2.5 μm). The analysis occurred at 50°C with a flow rate of 1.2 mL/min and detection at 220 nm. A 10 μL sample was injected, and the mobile phase consisted of two components: mobile phase A, containing 0.1% formic acid in water (20%), and mobile phase B, containing 0.1% formic acid in acetonitrile (80%). The diluent was prepared by mixing acetonitrile and water at a 90:10 v/v ratio. The retention time for the analyte was determined to be 2.78 min. Accuracy exceeded 99%, and the correlation coefficient was greater than 0.999. The validated HPLC method was characterized as precise, accurate, and robust. Significantly, NMT was found to be susceptible to alkaline, acidic, and peroxide conditions during forced degradation testing. The stability-indicating method developed effectively separated the degradation products formed during stress testing, underlining its effectiveness in stability testing and offering accuracy, reliability, and sensitivity in determining NMT.

A validated LC-MS/MS method for determination of six Anti-SARS-CoV-2 drugs in plasma and its application for a pharmacokinetic study in rats

Antiviral treatment for COVID-19 is considered an effective tool in reducing the rate of severe cases and deaths. As of June 2023, a total of six small molecule antiviral drugs have been conditionally approved for marketing by the National Medical Products Administration (NMPA) within China. In this study, a method of HPLC-MS/MS was established and validated for the determination of six small molecule antiviral drugs in plasma using Lamivudine as an internal standard. The chromatographic separation was performed using gradient elution with an ACE 3 C18-PFP column (3.0 mm × 150 mm, 3 μm), and the mobile phase consisted of deionized water and acetonitrile/water (90:10, v/v), both with 10 mmol/L of ammonium acetate and 0.1 % ammonium hydroxide added. Quantitative analysis of the six small molecule drugs was carried out through selective reaction monitoring based on the positive ion spray ionization mode. The method exhibited excellent precision, accuracy, recovery, and linearity, and it was used to determine the pharmacokinetic characteristics in rats. Our work not only established a bioanalytical method for six small molecule antiviral drugs but also provided scientific references for clinical pharmacokinetic studies.

Simultaneous quantification of nirmatrelvir/ritonavir in human serum by LC-HRMS

In December 2021, the U.S. Food and Drug Administration (FDA) granted emergency authorization for Paxlovid® as an antiviral treatment for COVID-19. Paxlovid® is composed of two tablets, nirmatrelvir and ritonavir. Dose adjustment is necessary in cases of renal insufficiency. The aim of present study is to establish a LC-HRMS method for simultaneous determination of nirmatrelvir/ritonavir in human serum for therapeutic drug monitoring. Internal standard saquinavir was added in 25 μL human serum samples, and then the samples were precipitated with methanol. The analytes were separated by gradient elution on a C18 column, using a mobile phase of 0.1 % formic acid-water and methanol, at a flow rate of 0.4 mL/min. The injection volume was 2 μL, and the analysis time was 5 min. The determination of the analytes was performed by electrospray ionization in positive mode by full mass monitoring. The detected ions of nirmatrelvir, ritonavir and saquinavir were m/z 500.24792, 721.32004 and 671.39155, respectively. The linear concentration range for nirmatrelvir was 78.13-20000 ng mL-1, for ritonavir was 15.63-4000 ng mL-1 (r2＞0.9900). The accuracy ranged from 87.45 %∼104.63 %, and the intra-day and inter-day precision RSD was <15 %. The recovery of nirmatrelvir ranged from 98.72 %∼109.83 %, and that of ritonavir was 95.41∼112.36 %. The matrix effect of nirmatrelvir was 88.31∼97.73 %, and that of ritonavir was 85.17∼103.05 %. This method was used to measure the trough concentrations of nirmatrelvir/ritonavir in 17 patients. The trough concentration of nirmatrelvir was 1331.7-8352.5 ng/mL, and that of ritonavir was 53.4-1325.5 ng mL-1, with large individual differences. The method is simple, sensitive, specific, and reproducible, and can be used for monitoring the blood concentration and pharmacokinetic study of nirmatrelvir/ritonavir in COVID-19 patients.

Homogeneous liquid-liquid microextraction coupled with HPLC/DAD for determination of nirmatrelvir and ritonavir as COVID-19 combination therapy in human plasma

The study reports the development of a high-performance liquid chromatography/diode array detection method to measure the levels of nirmatrelvir and ritonavir in human plasma. These two antiviral medications are used for the treatment of COVID-19 and are marketed as Paxlovid®. The method employed sugaring-out induced homogeneous liquid-liquid microextraction to improve sensitivity. Optimization of the method was performed using the one variable at a time approach by adjusting several factors such as type of sugar, extractant, amount of sugar, volume of extractant, and pH of the aqueous sample to achieve the highest efficiency. The developed method was validated according to the Food and Drug Administration guidelines and demonstrated good linearity, accuracy, and precision. The range of linearity was from 1000 to 20,000 ng/mL for nirmatrelvir and 200 to 20,000 ng/mL for ritonavir with correlation coefficient values of 0.998 and 0.996, respectively. Selectivity studies revealed that no others peaks appeared in the retention times of the studied drugs. The stability of nirmatrelvir and ritonavir were also investigated through short term and three cycles of freeze-thaw, and both drugs were found stable. This analytical method could be useful for monitoring drug concentrations in patients undergoing treatment with these medications for COVID-19. In this work, for the first time, SULLME was used for the sensitive determination of nirmatrelvir and ritonavir in biological fluids. The developed method was able to determine both drugs in therapeutic levels with no need to sophisticated techniques like LC-MS. In addition to that, SULLME is considered a simple and green sample preparation in comparison with conventional sample preparation methods.

Population pharmacokinetic modeling and simulation for nirmatrelvir exposure assessment in Chinese older patients with COVID-19 infection

Nirmatrelvir is an effective component of Paxlovid, the first oral antiviral drug granted emergency use authorization by the FDA. Nirmatrelvir is prescribed extensively in older adult patients to treat the coronavirus disease 2019 (COVID-19) infection. In this study, population pharmacokinetic modeling with clinical study data was employed to explore the pharmacokinetic profile of nirmatrelvir in older adult Chinese patients with COVID-19 infection. The result suggests that the pharmacokinetic profile of nirmatrelvir can be described by a one-compartment model with first-order absorption and elimination in this study population. The calculated apparent clearance (CL/F), apparent volumes of distribution (V/F), and absorption rate constant (ka) for the typical patient were 4.16 L/h, 39.1 L, and 0.776, respectively. The area under the curve (AUC) of nirmatrelvir in the typical Chinese older adult was approximately three-fold higher than the AUCs in Chinese and Western young adult volunteers. At the same doses, the simulated AUCs were increased by 26%, 43%, 72%, and 135% in virtual populations with creatinine clearances of 60, 45, 30, and 15 mL/min, respectively. Our research provides an instructive reference for nirmatrelvir dose selection in older Chinese adults.

Tailoring two white chromatographic platforms for simultaneous estimation of ritonavir-boosted nirmatrelvir in their novel pills: degradation, validation, and environmental impact studies

As the COVID-19 pandemic is not yet over, Pfizer has launched the novel pill Paxlovid® (Nirmatrelvir (NMV) co-packaged with ritonavir (RIT)) as an effective medication for hospitalized and non-hospitalized patients. Making pharmaceutical analysis greener and more sustainable has lately become the main direction of the research community. In this context, two fast, green, and stability-indicating chromatographic methods were designed for the neat quantitative determination of NMV and RIT in their bulk and dosage forms. Method I is deemed the first electro-driven attempt for the assay of Paxlovid®. Herein, the optimized conditions of the Micellar Electrokinetic Chromatographic (MEKC) method were 50 mM borate buffer at pH 9.2 with 25 mM sodium lauryl sulfate (SDS) being used as the background electrolyte (BGE) on a deactivated fused silica capillary (50 cm effective length × 50 μm id). Method II was an isocratic reversed-phase HPLC separation method using Zorbax-Eclipse C18 (4.6 × 250 mm, 5 μm particle size) column and 50 mM ammonium acetate buffer at pH 5 and acetonitrile as mobile phase constituents at a flow rate of 1 mL min-1. For the sake of simplicity and increasing sensitivity, a single wavelength of 210 nm was used for the two methods to assay both drugs. Linear correlations between peak areas and concentration were observed in the ranges of 10-200 μg mL-1 for NMV and 5-100 μg mL-1 RIT in both methods. The impact of versatile stress conditions such as hydrolysis, oxidation, and photolysis on the stability of NMV and RIT was studied. Fortunately, both methodologies were able to separate both drugs from their degradants. Thus, the stability indicating power of the methods was proved. The derived methods were statistically validated in agreement with the ICH guidelines. Furthermore, the environmental friendliness and sustainability of these methods were investigated and compared with the cited methods using the holistic multicriteria evaluation tools namely Hexagon, AGREE, and RGB12 metrics. Conclusively, the proposed methods offered reliable, feasible, economic, white, and stability-indicating alternatives to the cited chromatographic methods.

Green adherent degradation kinetics study of Nirmatrelvir, an oral anti-COVID-19: characterization of degradation products using LC-MS with insilico toxicity profile

The SARS-CoV-2 virus sets up a global catastrophe, and countries all around the world made significant efforts to halt the spread. Nirmatrelvir (NMV) was lately approved by the FDA as a safe and well-tolerated oral direct-acting antiviral medication for SARS-CoV-2 virus infection. Therefore, a fast completely validated stability indicating method was established-for the first time- for NMV determination. The study used NaOH, HCl, neutral, H₂O₂, and sunlight to test NMV stability under various stress conditions followed by kinetics degradation investigation and derivation of Arrhenius plot. The analysis was performed using Agilent Zorbax Eclipse-C18 column (5 µm, 4.6 × 250 mm) with a mobile phase consisting of acetonitrile: 50 mM ammonium acetate, pH = 5 (50:50, v/v, respectively) at a flow rate of 1.0 mL/min with 5 min run time. Diode array detector (DAD) was set at 225 nm to quantify NMV at the concentration range of 5-500 µg/mL with LOD and LOQ of 0.6 and 2 µg/mL, respectively. Method's greenness was assessed using different metrics including Analytical Eco-Scale, Greenness Assessment Procedure Index, GAPI, and Analytical Greenness, AGREE. A thorough study of stress stability revealed that NMV was more susceptible to alkaline hydrolysis compared with acid hydrolysis. In contrast, it was found that NMV remained stable when subjected to oxidative, neutral, and sun-induced degradation conditions. Moreover, acid and alkali-induced hydrolysis were found to follow pseudo first order kinetics. Consequently, the half lifetime of the studied degradation conditions at room temperature were calculated using the Arrhenius plot. The mechanism of the degradation pathways under stress circumstances was proposed using LC-MS-UV. Toxicities of the proposed degradation products were assessed using ProTox-II, along with the parent medication NMV, and were shown to be hardly hazardous.