Simple and cost-effective liquid chromatographic method for determination of pyrimethamine in whole blood samples dried on filter paper

Detection and quantification of Covid-19 antiviral drugs in biological fluids and tissues

Since coronavirus disease 2019 (COVID-19) started as a fast-spreading pandemic, causing a huge number of deaths worldwide, several therapeutic options have been tested to counteract or reduce the clinical symptoms of patients infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently, no specific drugs for COVID-19 are available, but many antiviral agents have been authorised by several national agencies. Most of them are under investigation in both preclinical and clinical trials; however, pharmacokinetic and metabolism studies are needed to identify the most suitable dose to achieve the desired effect on SARS-CoV-2. Therefore, the efforts of the scientific community have focused on the screening of therapies able to counteract the most severe effects of the infection, as well as on the search of sensitive and selective analytical methods for drug detection in biological matrices, both fluids and tissues. In the last decade, many analytical methods have been proposed for the detection and quantification of antiviral compounds currently being tested for COVID-19 treatment. In this review, a critical discussion on the overall analytical procedure is provided, i.e (a) sample pre-treatment and extraction methods such as protein precipitation (PP), solid-phase extraction (SPE), liquid–liquid extraction (LLE), ultrasound-assisted extraction (UAE) and QuEChERS (quick, easy, cheap, effective, rugged and safe), (b) detection and quantification methods such as potentiometry, spectrofluorimetry and mass spectrometry (MS) as well as (c) methods including a preliminary separation step, such as high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) coupled to UV–Vis or MS detection. Further current trends, advantages and disadvantages and prospects of these methods have been discussed, to help the analytical advances in reducing the harm caused by the SARS-CoV-2 virus.

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Fourteen antiviral drugs were tested to counteract the effects of COVID-19.

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A review of analytical methods for antivirals detection is presented.

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Method validation, drugs extraction, separation and detection are discussed.

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LC-MS and MS/MS is mostly used for accurate and sensitive drugs quantification.

LC-MS/MS method for the simultaneous analysis of seven antimalarials and two active metabolites in dried blood spots for applications in field trials: Analytical and clinical validation

In epidemiological studies, antimalarials measurements in blood represent the best available marker of drugs exposure at population level, an important driver for the emergence of drug resistance. We have developed a liquid chromatography-tandem mass spectrometry method (LC-MS/MS) for the simultaneous quantification of 7 frequently used antimalarials (amodiaquine, chloroquine, quinine, sulfadoxine, pyrimethamine, mefloquine, lumefantrine) and 2 active metabolites (N-desethyl-amodiaquine, desbutyl-lumefantrine) in 10-μl dried blood spots (DBS). This sampling approach is suitable for field studies wherein blood samples processing, transportation and storage are problematic. Sample preparation included extraction from a 3 mm-disk punched out of the DBS with 100-μl of methanol + 1% formic acid containing deuterated internal standards for all drugs. Good performances were achieved in terms of trueness (-12.1 to +11.1%), precision (1.4-15.0%) and sensitivity, with lower limits of quantification comprised between 2 ng/ml (sulfadoxine) and 20 ng/ml (chloroquine, quinine, pyrimethamine, mefloquine, lumefantrine and desbutyl-lumefantrine). All analytes were stable in DBS kept for 24 h at room temperature and at 37 °C. The developed assay was applied within the frame of a pharmacokinetic study including 16 healthy volunteers who received a single dose of artemether-lumefantrine. Lumefantrine concentrations in plasma and in DBS were highly correlated (R = 0.97) at all time points, confirming the assumption that lumefantrine concentrations determined in DBS confidently reflect blood concentrations. The blood/plasma ratio of 0.56 obtained using the Bland-Altman approach (and corresponding to the slope of the linear regression) is in line with very low penetration of lumefantrine into red blood cells. This sensitive multiplex LC-MS/MS assay enabling the simultaneous analysis of antimalarials in DBS is suitable for epidemiological studies in field conditions.

Trimester-Specific Population Pharmacokinetics and Other Correlates of Variability in Sulphadoxine-Pyrimethamine Disposition Among Ugandan Pregnant Women

Background

Sulphadoxine–pyrimethamine (SP) is widely used as an intermittent preventive treatment for malaria in pregnancy (IPTp). However, pharmacokinetic studies in pregnancy show variable and often contradictory findings. We describe population and trimester-specific differences in SP pharmacokinetics among Ugandan women.

Methods

SP (three tablets) were administered to 34 nonpregnant and 87 pregnant women in the second trimester. Seventy-eight pregnant women were redosed in the third trimester. Blood was collected over time points ranging from 0.5 h to 42 days postdose. Data on the variables age, body weight, height, parity, gestational age, and serum creatinine, alanine transaminase and albumin levels were collected at baseline. Plasma drug assays were performed using high-performance liquid chromatography with ultraviolet detection. Population pharmacokinetic analysis was done using NONMEM software.

Results

A two-compartment model with first-order absorption and a lag time best described both the sulphadoxine and pyrimethamine data. Between trimesters, statistically significant differences in central volumes of distribution (V₂) were observed for both drugs, while differences in the distribution half-life and the terminal elimination half-life were observed for pyrimethamine and sulphadoxine, respectively. Significant covariate relationships were identified on clearance (pregnancy status and serum albumin level) and V₂ (gestational age) for sulphadoxine. For pyrimethamine, clearance (pregnancy status and age) and V₂ (gestational age and body weight) were significant. Considering a 25 % threshold for clinical relevance, only differences in clearance of both drugs between pregnant and nonpregnant women were significant.

Conclusion

While clinically relevant differences in SP disposition between trimesters were not seen, increased clearance with pregnancy and the increasing volume of distribution in the central compartment with gestational age lend support to the revised World Health Organization guidelines advocating more frequent dosing of SP for IPTp.

Investigation of antimalarial drug pyrimethamine and its interaction with dsDNA by electrochemical and spectroscopic techniques

The electrochemical behavior of the antimalarial drug pyrimethamine (PMT) was examined at a screen printed carbon electrode (SPCE) in different aqueous supporting electrolytes using cyclic voltammetry (CV) and differential pulse voltammetry (DPV).

Dried blood spots in bioanalysis of antimalarials: relevance and challenges in quantitative assessment of antimalarial drugs

Malaria is the leading parasitic disease in emerging countries. Therapeutic drug monitoring of antimalarial drugs is becoming increasingly important due to their spreading resistance. Measuring systemic antimalarial drug concentrations is also vital for safety and PK evaluations during clinical development. The dried blood spot (DBS) technique is a convenient alternative sample-collection method to venipuncture, especially in resource -limited areas where the clinical studies of antimalarials are usually carried out. Various bioanalytical methods for antimalarial drug estimation utilizing DBS sampling have been reported. This review discusses the applicability and relevance of DBS in quantitative assessment of antimalarial drugs, the advantages and drawbacks of DBS, and the difficulties encountered during its implementation.

Biodegradable long circulating cellular carrier for antimalarial drug pyrimethamine

OBJECTIVE

The objective of the present study was to develop targeted engineered nanoerythrosomes based intravenous formulation of antimalarial drug pyrimethamine.

MATERIAL AND METHODS

The nanoerythrosomes formulation was developed by sonication method and optimized for effective drug loading at variable drug concentration, surface morphology, viscosity and sedimentation volume.

RESULTS

The in vitro drug release of formulated product was found to be delayed after 8 hours, having good stability at 4 ± 1°C and showing controlled in vivo release. Tissue distribution studies showed higher accumulation of drug in the liver (18.71 ± 1.4 μg/ml) (P < 0.05) at 1 hour in case of pyrimethamine-loaded nanoerythrosomes as compared to that in free drug (12.82 ± 0.7 μg/ml). Higher amount of drug, i.e. 14.18 ± 0.9 μg/ml (P < 0.05), was found after 24 hours in the liver in case of pyrimethamine-loaded nanoerythrosomes as compared to free drug concentration of 9.72 ± 0.5 μg/ml).

DISCUSSION

Data showed that developed pyrimethamine-loaded nanoerythrosomes hold promise for targeting and controlling the release of drug and for improving treatment of malaria when they are combined with rapid acting antimalarials such as artemisinin.

CONCLUSION

A decrease in the concentration of pyrimethamine in kidneys and lungs after 24 hours was observed as compared to that observed after 1 hour, showing no or little involvement of these organs in the clearance of drug-loaded nanoerythrosomes.

Determination of drug concentrations using dried blood spots: investigation of blood sampling and collection techniques in Crl:CD(SD) rats

Dried bloodspot (DBS) technology has been available for many decades but only in the last five years has it been considered for routine bioanalysis of blood samples collected on preclinical and clinical studies as part of a drug development programme. Advantages of using DBS versus typical plasma samples include smaller blood volumes, less processing of the samples (e.g. no centrifugation) and no requirement for storing or shipping of the samples at frozen temperatures. The current study compared blood concentrations (AUC0− t and Cmax) from rats given an oral dose of acetaminophen (APAP) using two different sampling sites (caudal venepuncture versus tail snip), two different collection methods (3 separate 15 μL ethylenediaminetetraacetic acid [EDTA]-coated capillary tubes versus an EDTA integrated capillary blood collection system) and variability between blood spots on one card. There were no noteworthy differences (i.e. two-fold or greater) in blood concentrations of APAP using the different sites or methods. Furthermore, comparisons of the APAP blood concentrations in the original spot to a duplicate bloodspot from the same bloodspot card were within 12% of the original concentration.

Validation of individual quantitative methods for determination of cytochrome P450 probe substrates in human dried blood spots with HPLC-MS/MS

BACKGROUND

Robust individual reversed-phase HPLC-MS/MS methods have been validated for the quantitative bioanalysis of caffeine, flurbiprofen, midazolam, omeprazole and rosiglitazone in dried blood spot samples prepared from small volumes (15 µl) of human blood. Samples were punched and the resulting discs were extracted for analysis with methanol. Detection was by TurboIonSpray™ ionization combined with selected reaction monitoring MS.

RESULTS

The validated analytical concentration ranges for caffeine, flurbiprofen, midazolam, omeprazole and rosiglitazone were 250 to 25,000 ng/ml, 100 to 10,000 ng/ml, 0.35 to 72 ng/ml, 5 to 1000 ng/ml and 2.5 to 1000 ng/ml, respectively, and were appropriate to measure circulating concentrations for these analytes at therapeutic doses. The within-run precision and bias values for all methods were less than 15%. All compounds were stable in dried blood spots stored at room temperature and protected from moisture for at least 5 days and in whole blood for 2 h at 37°C.

CONCLUSION

This work demonstrates that quantitative analysis of a drug extracted from dried blood spots can provide high-quality data while minimizing the volume of blood withdrawn from volunteers.

Assay for screening for six antimalarial drugs and one metabolite using dried blood spot sampling, sequential extraction and ion-trap detection

BACKGROUND

More parasites are becoming resistant to antimalarial drugs, and in many areas a change in first-line drug treatment is necessary. The aim of the developed assay is to help determine drug use in these areas and also to be a complement to interviewing patients, which will increase reliability of surveys.

RESULTS

This assay detects quinine, mefloquine, sulfadoxine, pyrimethamine, lumefantrine, chloroquine and its metabolite desethylchloroquine in a 100-µl dried blood spot. Most of the drugs also have long half-lives that make them detectable at least 7 days after administration. The drugs are extracted from the dried blood spot with sequential extraction (due to the big differences in physicochemical properties), solid-phase extraction is used as sample clean-up and separation is performed with gradient-LC with MS ion-trap detection.

CONCLUSION

Detection limits (S/N > 5:1) at 50 ng/ml or better were achieved for all drugs except lumefantrine (200 ng/ml), and thus can be used to determine patient compliance. A major advantage of using the ion-trap MS it that it will be possible to go back into the data and look for other drugs as needed.

A simple cost-effective high performance liquid chromatographic assay of sulphadoxine in whole blood spotted on filter paper for field studies

Background

Artesunate plus sulphadoxine-pyrimethamine is one of the four artemisinin-based combination therapies currently recommended by WHO as first-line treatment for falciparum malaria. Sulphadoxine-pyrimethamine is also used for intermittent preventive treatment for malaria in pregnancy. Drug use patterns and drug pharmacokinetics are important factors impacting the spread of drug resistant parasites hence it is imperative to monitor the effect of pharmacokinetic variability on therapeutic efficacy. Unfortunately, information on the pharmacokinetics of sulphadoxine in children and pregnant women with malaria is very limited. Methods for the assay of sulphadoxine-pyrimethamine have been previously reported, but they are not cost-effective and practicable in analytical laboratories in low resource areas where malaria is endemic. Efforts in this study were thus devoted to development and evaluation of a simple, cost-effective and sensitive method for quantification of sulphadoxine in small capillary samples of whole blood dried on filter paper.

Methods

Sulphadoxine was determined in whole blood by reversed-phase high performance liquid chromatography with UV detection at 340 nm. Sulisoxazole (SLX) was used as internal standard. Chromatographic separation was achieved using a Beckman Coulter ODS C₁₈ and a mobile phase consisting of 0.05 M phosphate buffer-methanol-acetonitrile (70:17:13 V/V/V) containing 1% triethylamine solution.

Results

Standard curves from sulphadoxine-spiked blood added to filter paper were linear over the concentration range studied. Linear regression analysis yielded correlation coefficient r² > 0.99 (n = 6). Extraction recoveries were about 82-85%. The limit of quantification was 120 ng/ml while the within and between assay coefficient of variations were < 10%. The inter-day precision was < 5.8% and inter-day accuracy ranged from 4.1 to 5.3%. There was no interference from endogenous compounds or any of the commonly used anti-malarial, analgesic and anti-infective drugs with the peaks of SDX or the internal standard.

Conclusion

The recovery and accuracy of determination of SDX from whole blood filter paper samples using the method described in this study is satisfactory, thus making the method a valuable tool in epidemiological studies and therapeutic drug monitoring in developing endemic countries. Furthermore, the applicability of the method in studying the pharmacokinetic disposition of SDX in a patient suggests that the method is suitable in malaria endemic areas.

Lack of impact of artesunate on the disposition kinetics of sulfadoxine/pyrimethamine when the two drugs are concomitantly administered

OBJECTIVE

To determine the effect of artesunate (AT) on the disposition kinetics of sulfadoxine/pyrimethamine (SP) in humans.

METHODS

In a randomized cross-over study, 16 healthy volunteers were given a dose of three SP tablets containing 500 mg of sulfadoxine (SDX) and 25 mg of pyrimethamine (PYR) (=SP group), while the second arm received three SP tablets + two AT tablets of 200 mg in total followed by 100 mg AT for the next 4 days (SP+AT group). Blood samples (100 microl) were collected by means of a finger prick and dried on filter paper. The blood spots were wrapped in polythene folders and stored at room temperature until analysis. The samples were assayed using high-performance liquid chromatographic methods.

RESULTS

The peak concentration C(max)), time required to attain peak concentration (T(max)), half-life (t ((1/2))) and area under the plasma concentration-time curve (AUC) were determined. The C(max) of SDX were 92.9 and 98.9 microg/ml for the SP and SP+AT arms, respectively; for PYR, these were 0.86 and 0.79 microg/ml, respectively. The T(max) of SDX were 10 and 8 h for the SP and SP+AT arms, respectively; for PYR, these were 4.0 and 3.0 h, respectively. The AUC(0-288) of SDX were 15,840 and 18,876 microg/ml h for the SP and SP+AT arms, respectively; for PYR, they were 124 and 112 microg/ml h, respectively. The t ((1/2)) of values for SDX were 165 and 180 h for the SP and SP+AT arms, respectively; for PYR, these were 158 and 177 h, respectively. There was no statistically significant difference between the C(max), T(max), AUC(0-288) and t ((1/2)) between the two arms (p > 0.05).

CONCLUSION

Taking AT concomitantly with SP does not have any impact in the disposition of SP.

Simultaneous determination of monodesethylchloroquine, chloroquine, cycloguanil and proguanil on dried blood spots by reverse-phase liquid chromatography

A method for simultaneous analysis of chloroquine, proguanil and their metabolites from a whole blood sample (80 microL) dried on a filter paper was developed. Sample preparation included a liquid extraction from the filter paper, followed by a solid-phase extraction (C18 Bond Elut cartridge). Separation was obtained by reverse-phase liquid chromatography (HPLC) using a gradient elution on an X-Terra column; UV detection was made at 254 nm. This assay was linear between 150 and 2500 ng mL(-1) for chloroquine (and metabolite) and 300 and 2500 ng mL(-1) for proguanil and cycloguanil. The lower limit of quantification was close to 50 ng mL(-1) for chloroquine (and its metabolite) and 100 ng mL(-1) for proguanil (and its metabolite). No chromatographic interference from endogenous compounds or other tested anti-malarial drugs was evidenced. Chromatographic separation takes about 40 min with a coefficient of variation below 10.3% for within- and between-batch precision. The paper sampling method was validated in 10 healthy subjects treated by Savarine. The stability of compounds and metabolites on the filter paper was evaluated at four temperatures (-20, +4, 20 and 50 degrees C) and for 1, 5 and 20 days. Cycloguanil concentrations were not influenced by storage conditions, whereas, high temperatures and prolonged storage decreased chloroquine and proguanil levels. The proposed HPLC assay is accurate, precise and cost-effective; it can be used for pharmacokinetic and epidemiological studies on anti-malarial treatments.

Applicability of bioanalysis of multiple analytes in drug discovery and development: review of select case studies including assay development considerations

The development of sound bioanalytical method(s) is of paramount importance during the process of drug discovery and development culminating in a marketing approval. Although the bioanalytical procedure(s) originally developed during the discovery stage may not necessarily be fit to support the drug development scenario, they may be suitably modified and validated, as deemed necessary. Several reviews have appeared over the years describing analytical approaches including various techniques, detection systems, automation tools that are available for an effective separation, enhanced selectivity and sensitivity for quantitation of many analytes. The intention of this review is to cover various key areas where analytical method development becomes necessary during different stages of drug discovery research and development process. The key areas covered in this article with relevant case studies include: (a) simultaneous assay for parent compound and metabolites that are purported to display pharmacological activity; (b) bioanalytical procedures for determination of multiple drugs in combating a disease; (c) analytical measurement of chirality aspects in the pharmacokinetics, metabolism and biotransformation investigations; (d) drug monitoring for therapeutic benefits and/or occupational hazard; (e) analysis of drugs from complex and/or less frequently used matrices; (f) analytical determination during in vitro experiments (metabolism and permeability related) and in situ intestinal perfusion experiments; (g) determination of a major metabolite as a surrogate for the parent molecule; (h) analytical approaches for universal determination of CYP450 probe substrates and metabolites; (i) analytical applicability to prodrug evaluations-simultaneous determination of prodrug, parent and metabolites; (j) quantitative determination of parent compound and/or phase II metabolite(s) via direct or indirect approaches; (k) applicability in analysis of multiple compounds in select disease areas and/or in clinically important drug-drug interaction studies. A tabular representation of select examples of analysis is provided covering areas of separation conditions, validation aspects and applicable conclusion. A limited discussion is provided on relevant aspects of the need for developing bioanalytical procedures for speedy drug discovery and development. Additionally, some key elements such as internal standard selection, likely issues of mass detection, matrix effect, chiral aspects etc. are provided for consideration during method development.

Simultaneous quantitative analysis of the antimalarials pyrimethamine and sulfamethoxypyrazine in plasma samples using liquid chromatography/tandem mass spectrometry

The work presented here deals with the development of a quantitative tool for the simultaneous determination of sulfamethoxypyrazine (sulfalene)/pyrimethamine in plasma. The chromatography used only takes 12.5 min, allowing a fast sample turnover time. Relative standard deviation of retention times was never above 3.48% (n = 66). Adequate sample clean-up was achieved by a simple and relatively fast liquid/liquid extraction. In this way, ionisation suppression effects, typical for more simple sample clean-up procedures, could be avoided resulting in absolute plasma effects of maximum -17.1% for sulfalene, -16.1 for the internal standard (IS), and 12% for pyrimethamine. For both pyrimethamine and sulfalene, quadratic calibration curves from 0.00101 to 0.807 microg/mL for pyrimethamine and from 0.271 to 216 microg/mL for sulfalene gave the best fit. Mean coefficients of determination (R2) were 0.9951 (n = 6, CV% 0.39) for pyrimethamine and 0.9942 (n = 6, CV% 0.13) for sulfalene. Precision was below 9.35% for pyrimethamine and 13.9% for sulfalene. Inaccuracy remained below 15% at all cases. The optimised method was used for a time-course study of the sulfalene/pyrimethamine combination concentration in plasma of patients treated with Co-Arinate, a new curative antimalaria-medicine.