Quantitative analysis of trimethylsilyl derivative of hydroxyurea in plasma by gas chromatography–mass spectrometry

MicroNIR/Chemometrics Assessement of Occupational Exposure to Hydroxyurea

Portable Near Infrared spectroscopy (NIRs) coupled to chemometrics was investigated for the first time as a novel entirely on-site approach for occupational exposure monitoring in pharmaceutical field. Due to a significant increase in the number of patients receiving chemotherapy, the development of reliable, fast, and on-site analytical methods to assess the occupational exposure of workers in the manufacture of pharmaceutical products, has become more and more required. In this work, a fast, accurate, and sensitive detection of hydroxyurea, a cytotoxic antineoplastic agent commonly used in chemotherapy, was developed. Occupational exposure to antineoplastic agents was evaluated by collecting hydroxyurea on a membrane filter during routine drug manufacturing process. Spectra were acquired in the NIR region in reflectance mode by the means of a miniaturized NIR spectrometer coupled with chemometrics. This MicroNIR instrument is a very ultra-compact portable device with a particular geometry and optical resolution designed in such a manner that the reduction in size does not compromise the performances of the spectrometer. The developed method could detect up to 50 ng of hydroxyurea directly measured on the sampling filter membrane, irrespective of complexity and variability of the matrix; thus extending the applicability of miniaturized NIR instruments in pharmaceutical and biomedical analysis.

Hydroxyurea: Analytical techniques and quantitative analysis

Hydroxyurea is a potent disease-modifying therapeutic agent with efficacy for the treatment of sickle cell anemia. When administered at once-daily oral doses that lead to mild marrow suppression, hydroxyurea leads to substantial and sustained fetal hemoglobin induction, which effectively inhibits erythrocyte sickling. When escalated to maximum tolerated dose, hydroxyurea has proven laboratory and clinical effects for both children and adults with sickle cell anemia. However, there is substantial inter-patient variability with regard to the optimal dosing regimen, as well as differences in treatment-related toxicities and responses that may be explained by hydroxyurea pharmacokinetics and pharmacogenetics. Addressing the safety and efficacy of hydroxyurea treatment requires quantitative and accurate drug analysis, and various laboratory techniques have been established. We review the historical and current analytical techniques for measuring hydroxyurea concentrations accurately, and discuss clinical settings where quantitative analysis can increase understanding and safety of this important therapeutic agent, and ultimately improve patient outcomes.

Isotope-dilution gas chromatography-mass spectrometry method for the analysis of hydroxyurea

BACKGROUND

Hydroxyurea is used in the treatment of various malignancies and sickle cell disease. There are limited studies on the pharmacokinetics of hydroxyurea, particularly in pediatric patients. An accurate, precise, and sensitive method is needed to support such studies and to monitor therapeutic adherence. We describe a novel gas chromatography-mass spectrometry (GC-MS) method for the determination of hydroxyurea concentration in plasma using stable labeled hydroxyurea C N2 as an internal standard.

METHODS

The method involved an organic extraction followed by the preparation of trimethylsilyl (TMS) derivatives of hydroxyurea for GC-MS selected ion-monitoring analysis. The following mass-to-charge (m/z) ratio ions for silated hydroxyurea and hydroxyurea C N2 were monitored: hydroxyurea-quantitative ion 277, qualifier ions 292 and 249; hydroxyurea C N2-quantitative ion 280, qualifier ion 295. This method was evaluated for reportable range, accuracy, within-run and between-run imprecisions, and limits of quantification.

RESULTS

The reportable range for the method was 0.1-100 mcg/mL. All results were accurate within an allowable error of 15%. Within-run and between-run imprecisions were <15%. Samples were stable for at least 4 hours at room temperature, 2 months at -20°C, and 6 months at -70°C, and after 3 freeze/thaw cycles. Extraction efficiency for 1-, 5-, 10-, and 50-mcg/mL samples averaged 2.2%, 1.8%, 1.6%, and 1.4%, respectively.

CONCLUSIONS

The isotope-dilution GC-MS method for analysis of hydroxyurea described here is accurate, sensitive, precise, and robust. Its characteristics make the method suitable for supporting pharmacokinetic studies and/or clinical therapeutic monitoring.

Analysis of anticancer drugs: a review

In the last decades, the number of patients receiving chemotherapy has considerably increased. Given the toxicity of cytotoxic agents to humans (not only for patients but also for healthcare professionals), the development of reliable analytical methods to analyse these compounds became necessary. From the discovery of new substances to patient administration, all pharmaceutical fields are concerned with the analysis of cytotoxic drugs. In this review, the use of methods to analyse cytotoxic agents in various matrices, such as pharmaceutical formulations and biological and environmental samples, is discussed. Thus, an overview of reported analytical methods for the determination of the most commonly used anticancer drugs is given.

Determination of hydroxyurea in serum or plasma using gas chromatography-mass spectrometry (GC-MS)

Hydroxyurea is an antineoplastic drug, which is also widely used in the treatment of sickle cell disease. Various methods including colorimetry, high performance liquid chromatography, and gas chromatography-mass spectrometry (GC-MS) are available for the assay of hydroxyurea. In the gas chromatography method described, the drug is extracted from serum, plasma, or urine using ethyl acetate and phosphate buffer (pH 6). The organic phase containing drug is separated and dried under a stream of nitrogen. After trimethylsilyl derivatization, samples are analyzed using GC-MS. Quantitation of the drug in a sample is achieved by comparing responses of the unknown sample to the responses of the calibrators using selected ion monitoring. Tropic acid is used as an internal standard.

Plasma hydroxyurea determined by gas chromatography-mass spectrometry

Hydroxyurea treatment is efficiently used to ameliorate the clinical course of patients affected with sickle cell disease. To understand the patient's wide variation in the clinical response to that drug and monitor its plasma levels, a new method was developed and validated. Fifty microL plasmatic samples containing hydroxyurea are added with internal standard, deproteinized, evaporated to dryness, silanized, and analyzed by gas chromatography-mass spectrometry, which operates in the selected ion mode after electron impact fragmentation. Linearity was found to extend to at least 100mg/L. Over a 1-25mg/L concentration range, coefficients of variation for intra-day and inter-day precision are 5.3% and 7.7%, respectively. Plasma blank-samples reveal endogenous hydroxyurea at a level <or=0.2mg/L. The performances of the method, which is fast and simple, encounter the analytical goals needed for evaluation of hydroxyurea treatment and for pharmacokinetic studies.