Development and validation of an assay for the measurement of gentamicin concentrations in dried blood spots using UHPLC-MS/MS

Gentamicin sulfate (GEN) is an aminoglycoside antibiotic with a narrow therapeutic range of plasma concentrations. The collection of venous blood represents a significant burden for patients, especially in neonatology. Dried blood spots (DBS) obtained from capillary blood can be an alternative for drug measurements in this particular population. This study aimed to develop and validate an assay for the quantification of GEN in DBS using UHPLC-MS/MS. Total GEN concentrations were obtained by adding the individual concentrations of the GEN forms C1, C1a, and C2. The assay used a DBS disk containing approximately 17 μL of blood for GEN quantitation in the range of 0.1-40 mg L^-1. Measurement accuracy for total GEN was in the range of 102.6-108.6%, inter-assay precision was 11.3-13.1% and intra-assay precision was 9.1-12.8.% GEN was stable for 21 days at - 20 and 8 °C, but only for 24 h at room temperature. Blood Hct affected the accuracy within acceptable limits (93.8-95% at Hct% of 30, 104.3-113% at Hct% of 50). Blood spotted volume did not affect GEN measurement accuracy. Concentrations of GEN in DBS obtained after heel pricks were correlated to plasma levels in a small cohort of neonatal patients. However, percentual differences between estimated plasma concentrations and actual plasma levels presented values between - 64-35.3% (average difference of - 1.9%). The use of DBS for the measurement of GEN concentrations can increase access to TDM of this antibiotic due to the ease of sample collection and the facilitated specimen transportation logistics when testing is not available onsite.

Sensitive determination of gentamicin in plasma using ion-exchange solid-phase extraction followed by UHPLC-MS/MS analysis

Background

Therapeutic drug monitoring (TDM) of gentamicin sulfate (GEN) is usually recommended, particularly in critical patients. Only a few reports had described the determination of GEN in plasma or plasma using LC-MS/MS.

Objective

This study aimed to develop and validate a sensitive ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) assay for the quantification of GEN in small volumes of human plasma.

Results

The use of a very low concentration of the ion-pairing agent HFBA allowed significant retention of the very polar GEN forms in a reversed phase UHPLC column. The solid-phase extraction (SPE) procedure allowed clean extracts, with no interferences detected in blank samples, and high sensitivity. The assay was linear on the range of 0.2–40 mg L⁻¹ of GEN complex. The combined GEN complex had inter-assay CV of 8.8–10.0%, intra-assay CV of 10.2–11.0%, and accuracy of 96.8–104.0%. The assay was applied to 17 clinical samples obtained from neonate patients. Measured concentrations were in the range of 0.15–3.57 mg L⁻¹ for GEN C1, 0.12–3.55 mg L⁻¹ for GEN C1a, 0.20–5.77 mg L⁻¹ for GEN C2, and 0.47–12.88 mg L⁻¹ for the GEN complex, all within the linear range of the assay.

Conclusion

A sensitive assay for the quantification of gentamicin in plasma using anion-exchange SPE and UHPLC-MS/MS was validated. The assay can be used for TDM of gentamicin, particularly in centers with access to proper instrumentation and with a low demand for gentamicin measurements, where immunoassays are not cost-effective.

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Gentamicin was extracted from plasma using ion-exchange solid phase extraction.

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Chromatographic conditions were previously applied for amikacin and vancomycin.

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Gentamicin was measured with acceptable accuracy and precision using UHPLC-MS/MS.

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The assay was sensitive and had a linear range covering clinically relevant concentrations.

Omeprazole nanoparticles suspension: Development of a stable liquid formulation with a view to pediatric administration

Omeprazole (OME) is often used to treat disorders associated with gastric hypersecretion in children but a liquid pediatric formulation of this medicine is not currently available. The aim of this study is to develop OME loaded nanoparticles with a view to the obtention of a liquid pharmaceutical dosage form. Eudragit® RS100 was selected as the skeleton material in the inner core and pH-sensitive Eudragit® L100-55 was used as the outer coating of the nanoparticles prepared by the nanoprecipitation method. Pharmacological activity was evaluated by induction of ethanol ulcers in mice. The OME nanoparticles exhibited mean diameters of 174 nm (±17), polydispersity index of 0.229 (±0.01), zeta potential values of -13 mV (±2.60) and encapsulation efficiency of 68.1%. The in vivo pharmacological assessment showed the ability of nanoparticles to protect mice stomach against ulcer formation. The prepared suspension of OME nanoparticles represents effective therapeutic strategy in a liquid pharmaceutical form with the possibility of pediatric administration.