Reversed-phase liquid chromatographic method for the simultaneous determination of the antimalarial drugs sulfadoxine, pyrimethamine, mefloquine and its major carboxylic metabolite in plasma

Determination of sulfadoxine and pyrimethamine in microvolume human plasma using ultra high performance liquid chromatography-tandam mass spectrometry

To support the pharmacokinetic study of sulfadoxine (SD) and pyrimethamine (PM) in pregnant women and children, sensitive methods with small sample volume are desirable. Here we report a method to determine SD and PM with microvolume plasma samples: 5 µL plasma samples were cleaned up by protein precipitation with acetonitrile. The deuterated analytes were used as the internal standards. The samples after cleanup were injected onto an ACE Excel SuperC18 column (50 × 2.1 mm, 1.7 μm, Hichrom Limited) connected to a Waters I class UPLC coupled with a Sciex Triple Quad 6500+ Mass Spectrometer and eluted with water and acetonitrile both containing 0.1% formic acid in a gradient mode at 0.8mL/min. Detection utilized ESI+ as the ion source and MRM as the quantification mode. The precursor-to-product ion transitions m/z 311→245 for SD and 249→233 for PM were selected for quantification. The ion transitions for the corresponding internal standards were 315→249 for SD-d4 and 254→235 for PM-d3. The simplest linear regression weighted by 1/x was used for the calibration curves. The calibration ranges were 1-200 µg/mL SD and 2 - 1000ng/mL PM. The mean (± standard deviation) recoveries were 94.3±3.2% (SD) and 97.0±1.5% (PM). The validated method was applied to analysis of 1719 clinical samples, demonstrating the method is suitable for the pharmacokinetic study with samples collected up to day 28 post-dose.

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.

Liquid chromatographic–mass spectrometric assay for simultaneous pyrimethamine and sulfadoxine determination in human plasma samples

We present a liquid chromatographic-mass spectrometric assay for the simultaneous determination of sulfadoxine and pyrimethamine in human plasma samples. Sample clean-up was achieved by adding acetonitrile for protein precipitation. Gradient elution in only 10 min resulted in high throughput capability. Tandem mass spectrometric detection in multiple reaction monitoring was used for quantification. The developed analytical approach was successfully validated and was applied in the pharmacokinetic evaluation of the bioavailability between two sulfadoxine/pyrimethamine formulations available on the Eastern African market, using a cross-over design.

A validated HPLC method for determining residues of a dual active ingredient anti-malarial drug on manufacturing equipment surfaces

Analytical method validation, determining the recovery rate from the equipment surface and the stability of a potential contaminant are important steps of a cleaning validation process. A rapid, sensitive and reproducible reversed-phase high-performance liquid chromatographic method was developed for the determination of pyrimethamine (PYR) and sulfadoxine (SUL) in cleaning validation swab samples. The active compounds can be selectively quantified in a sample matrix containing detergent and swab material as low as 0.12 microg/ml. The swabbing procedure used on stainless steel coupons was validated and the stability of PYR and SUL in the swab samples was assessed. The calculated limit of contamination values for PYR (4.99 microg/cm2) and SUL (19.14 microg/cm2) were not exceeded during four consecutive equipment cleaning trials. This confirms that the desired level of cleanliness is achieved with the current cleaning procedures, which are consequently validated.

Simultaneous spectrophotometric determination of sulfadoxine and pyrimethamine in pharmaceutical formulations

This study was carried out to simultaneously determine quantitatively sulfadoxine and pyrimethamine in four brands of anti-malarial formulations. The reaction principle was based on the complexation reaction between the drugs (pi-donors) and chloranilic acid (pi-acceptor) giving rise to colour formation. The complexes of sulfadoxine and pyrimethamine absorbed maximally at 500 and 520 nm, respectively. The limits of detection of these complexes were 0.005 mg/ml for pyrimethamine and 0.010 mg/ml for sulfadoxine. Calibration graphs were linear at 0.015 mg/ml for pyrimethamine and 0.020 mg/ml for sulfadoxine. Quantitative recovery experiments gave percentage range between 94.79 +/- RSD 3.85% and 98.04 +/- 2.21% for sulfadoxine and 93.75 +/- RSD 0.89% to 103 +/- 1.04% for pyrimethamine. Analysis by the Official method similarly gave percentages range of between 97.9 +/- 2.3% and 100.1 +/- 3.1% for sulfadoxine; 97.8 +/- 1.9% and 99.6 +/- 2.5% for pyrimethamine. Comparison of the two methods by Students t-test did not reflect any statistical difference (P > 0.05). These figures show that these brands of anti-malarial meet the Pharmacopoeia standard of 95-105%. We found this technique suitable for quality assurance of these drugs. The sensitivity, accuracy, simplicity of this technique also commends it for field studies.

Development of a method for the determination of pyrimethamine concentrations in feeds by ion-pairing high-performance liquid chromatography

An ion-pairing reversed-phase high-performance liquid chromatography (HPLC) method with diode array detection at 280 nm was developed to determine pyrimethamine concentrations in feed for laying hens. Pyrimethamine was extracted with a mixture of 5% isobutanol and 95% benzene, and the extract was cleaned up on an alumina column. The drug was eluted from an Intersil ODS-3V column (250 by 4.6 mm) with a mixture of 25% acetonitrile and 75% water (vol/vol) containing 0.01 M tetramethylammonium chloride as an ion-pairing agent and adjusted with acetic acid to pH 3.5. The flow rate was 1.0 ml/min. Mean recovery of pyrimethamine from supplemented feeds at concentrations of 2, 4, and 5 microg/g of feed were 100.5, 103.5, and 100.8%, respectively. Precision within a day ranged from 4.3 to 7.0% for the three concentrations, and day-to-day precision was 5.3% for feed supplemented at a concentration of 4 microg/g. No chromatographic interference was detected from other 2,4-diaminopyrimidine compounds or other major drugs used in poultry.

A rapid spectrophotometric method for the determination of mefloquine hydrochloride

A simple ultraviolet spectrophotometric method for the estimation of mefloquine hydrochloride in methanol (ME(2)) has been developed and has been compared with the reported ultraviolet spectrophotometric method in 0.1 N hydrochloric acid (ME(1)). Analytical parameters such as stability, selectivity, accuracy and precision have been established for both the methods and evaluated statistically to assess the application of the individual methods. Both the methods were compared with the existing pharmacopoeial method for estimation of the drug. Both the methods were found to have the advantages for simplicity, stability, sensitivity, reproducibility and accuracy for using as an alternate to the existing non-spectrophotometric methods for the routine analysis of the drug in pharmaceutical formulations and also in pharmaceutical investigations involving mefloquine hydrochloride.

High-performance liquid chromatographic assay for the simultaneous determination of sulfadoxine and pyrimethamine from whole blood dried onto filter paper

A method using solid-phase extraction and high-performance liquid chromatography is evaluated for the simultaneous determination of sulfadoxine and pyrimethamine from 0.1 ml of whole blood dried onto filter paper. Extraction recoveries are about 60% for both drugs. The coefficient of variation for intra-assay precision, inter-assay precision and accuracy is less than 10% for sulfadoxine (10-100 microg/ml) and pyrimethamine (1-10 microg/ml).

Determination of sulfadoxine in human blood plasma using packed-column supercritical fluid chromatography

A sensitive, rapid, selective and reproducible method has been developed to measure plasma levels of sulfadoxine, 4-Amino-N-(5, 6-dimethoxy-4-pyrimidinyl) benzensulfonamide; in healthy, human volunteers using packed-column super-critical fluid chromatography. Omeprazole, 5-methoxy-2-[[(4-methoxy-3, 5-di-methyl-2-pyridinyl)methyl]sulfinyl]-1H-benzimidazole; was used as the internal standard (i.s.) at 15.0 microg/ml. The drug and the i.s. were extracted from plasma using dichloromethane. Separation of sulfadoxine and i.s. was done on a Nucleosil (250x4.6 mm) 10 microm, RP-C18 column with 7.4% (v/v) methanol-modified supercritical fluid carbon dioxide (2.5 ml/min) as the mobile phase. The column temperature was 40 degrees C and the outlet pressure was set at 8.83 MPa. The detection was done using a UV-Vis detector set at 265 nm. The limit of quantification was 0.50 microg/ml using 1 ml plasma specimen. The mean extraction recovery of the drug from plasma was found to be 94.9%. The SFC method was directly compared to a published HPLC/UV method. With respect to speed and use of organic solvents SFC was found to be superior; while in all other aspects the results were similar to the published technique. The method has been successfully used to estimate the sulfadoxine levels in healthy human volunteers from 0 to 240 h following an oral dose of 500 mg of sulfadoxine in combination with 25 mg of pyrimethamine.

Stereospecific determination of mefloquine in biological fluids by high-performance liquid chromatography

A sensitive stereoselective HPLC method was developed for determination of mefloquine (MFQ) enantiomers in plasma, urine and whole blood. The assay involved liquid-liquid extraction of MFQ from biological fluids with a mixture of hexane and isopropanol in the presence of sodium hydroxide and derivatization of the residue by (+)-(S)-naphthylethylisocyanate (NEIC) as chiral derivatizing reagent. Separation of the resulting diastereomers was performed on a silica normal-phase column using chloroform-hexane-methanol (25:74:1) as the mobile phase with a flow-rate of 1 ml/min. Using 200 microl of plasma or whole blood, the limit of determination was 0.2 microg/ml with UV detection for both enantiomers. The limit of determination in 500 microl of urine was 0.08 microg/ml with UV detection.

Simultaneous determination of pyrimethamine and sulphadoxine in human plasma by high-performance liquid chromatography after automated liquid-solid extraction

A high-performance liquid chromatographic method with ultraviolet detection is described for the simultaneous measurement of pyrimethamine and sulphadoxine in human plasma. After an automated liquid-solid extraction on a C8 cartridge, the compounds are separated on a C18 column by isocratic elution; the mobile phase is methanol-acetonitrile-water (10:25:65, v/v/v) with triethylamine (1%) and adjusted to pH 5.6 with phosphoric acid. The eluent is monitored with an ultraviolet detector at 240 nm. The limit of quantification was 10 ng/ml for pyrimethamine and 22 microg/ml for sulphadoxine. No chromatographic interferences can be detected from endogenous compounds, other anti-malarial drugs or major drugs used for the treatment of children. Sulphadimethoxine is used as an internal standard. The method is accurate and precision is good with relative standard deviations lower than 6%. The chromatographic procedure takes 11 min. The method is comparatively rapid, simple, sensitive and can be used for therapeutic drug monitoring, clinical and pharmacokinetic studies.

Sulphadoxine concentrations in plasma, red blood cells and whole blood in healthy and Plasmodium falciparum malaria cases after treatment with Fansidar using high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic method using acetonitrile-methanol-(1M) perchloric acid-water (30:9:0.8:95, v/v/v/v) at a flow of 1.5 ml min-1 on mu-Bondapak C18 column with UV (254 nm) detection has been developed for the separation of sulphadoxine, sulphalene and sulphamethoxazole from other antimalarials. Calibration curves were linear in the range 0.5-100 micrograms ml-1. The limit of quantitation was 50 ng ml-1. Within-day and day-to-day coefficients of variation averaged 2.1 and 6.45%, respectively. The extraction recovery of sulphadoxine from plasma, red blood cells and whole blood was 90.28, 92.05 and 94.69%, respectively. The method has been used for the determination of sulphadoxine concentrations in plasma, red blood cells and whole blood of eight healthy and 50 Plasmodium falciparum malaria cases after administration of two tablets of Fansidar. Mean sulphadoxine concentration in plasma was higher than red blood cells or whole blood. Sulphadoxine concentration in plasma and whole blood of P. falciparum malaria cases was significantly higher as compared to healthy volunteers while it was the same in red blood cells. Sulphadoxine was absorbed much less in red blood cells than in plasma or whole blood.