A simple HPLC-UV Method for Therapeutic Drug Monitoring of Linezolid in human Plasma in low-resourced settings

OBJECTIVE: A high-performance liquid chromatography method for the estimation of Linezolid in human plasma was developed and validated. METHODS: Samples (100µµL) were deproteinized with acetonitrile and analyzed using LiChrospher 100, RP18e column with PDA detection at 254 nm. The flow rate of the isocratic mobile phase comprising of 0.1% formic acid in 1000 ml of water and acetonitrile in the ratio of 60:40 (v/v) was set at 1.0 ml/min. RESULTS: The calibration curve ranged from 0.50 to 20.0 µg/ml and was linear. The recovery ranged from 96% to 101%. The accuracy ranged from 98 to 101% and intra- and inter-day relative standard deviation was <4.58%. The method reliably eliminated interfering materials from plasma and R2 was 0.9973. The method described was applied to the determination of plasma LZD concentration in multi-drug-resistant tuberculosis patients who are treated with a dose of 600 mg LZD once daily. CONCLUSIONS: The developed method is suitable for determination of plasma LZD in routine care and considered feasible in less-resourced settings

Method Development and Validation for the Determination of Linezolid Drug in Human Plasma by Reversed-Phase High-Performance Liquid Chromatography

Objective:

Linezolid is a significant antibiotic used against severe infections initiated by multi-resistant bacterial pathogens.

Method:

Linezolid extraction from plasma is obtained using methanol. Chromatographic separation is achieved isocratically on a C18 column [Zorbax C18, 5 µm particle size, 150 mm ˟ 4.6 mm] making use of a mobile phase of acetonitrile / 0.05 M phosphate buffer, pH = 4.5 (30 : 70 v/v) at a flow rate of 1.2 mL/min with photodiode array detector DAD, at a wavelength of 256 nm.

Method:

Linezolid extraction from plasma is obtained using methanol. Chromatographic separation is achieved isocratically on a C18 column [Zorbax C18, 5 µm particle size, 150 mm ˟ 4.6 mm] making use of a mobile phase of acetonitrile / 0.05 M phosphate buffer, pH = 4.5 (30 : 70 v/v) at a flow rate of 1.2 mL/min with photodiode array detector DAD, at a wavelength of 256 nm.

Results :

The retention time of linezolid was 2.5 min. The analytical method was linear (r2 > 0.998) over the calibration range of 0.30 to 50.0 µg/mL. The extraction recoveries of linezolid range from 71.03 to 91.93 %. The limit of quantification and the limit of detection were 0.112 µg and 0.037 µg, respectively. The RSDs for intraday and interday assays were < 7.77 and 4.32 %, respectively. The intraday and interday accuracies were in the range 80.6-112 % and 77.44-104.85 %, respectively.

Conclusion:

The applied method is precise, accurate and appropriate for pharmacokinetic studies and therapeutic drug monitoring of linezolid in routine clinical practice.

A critical review of HPLC-based analytical methods for quantification of Linezolid

Linezolid is a synthetic antimicrobial agent belonging to the oxazolidinone class. Since its approval in the year 2000 until now, linezolid remains the main representative drug for the oxazolidinone class of drugs, which is used in therapy due to its unique mode of action, which involves inhibition of protein synthesis. As linezolid holds great importance in antimicrobial therapy, it is necessary to compile the various analytical methods that have been reported in the literature for its analysis. Analytical techniques used for pharmaceutical analyses and therapeutic drug monitoring play an important role in comprehending the aspects regarding bioavailability, bioequivalence, and therapeutic monitoring during patient follow-ups. Even though linezolid has had the approval for clinical use for more than 18 years now, most of the analytical methods for its determination reported in the scientific literature are the ones which utilize HPLC. Therefore, the present review provides a summary of the HPLC-based methods used in the determination and quantification of linezolid in different matrices since the time of its discovery.

Linezolid-A Review of Analytical Methods in Pharmaceuticals and Biological Matrices

Bacterial resistance to antibiotics is a growing phenomenon in the world. Considering the relevance of antimicrobials for population and the reduction in the registration of new antimicrobials by regulatory agencies, proper quality control is required to minimize the spread of bacterial resistance and ensure the effectiveness of a treatment, as well as safety for the patient. The recent addition to the antimicrobial world is the oxazolidinone classes of antibiotics, especially useful to treat infections caused by Gram-positive bacteria. Eperezolid and linezolid (LIN) are the two members of the oxazolidinone class of antibiotics. LIN was the first oxazolidinone approved by the Food and Drug Administration. The present review focuses on the analytical methods for the assessment of LIN in pharmaceuticals and biological matrices. The critical validation parameters like the linearity, limit of detection, limit of quantification are discussed for the individual method. Also the critical quality attributes like the sensitivity and the sample preparation techniques for bioanalytical methods are also discussed. Furthermore, some future trends that can be incorporated in the determination of similar drugs are also suggested.

Development and validation of a fast micro-extraction by packed sorbent UHPLC-PDA method for the simultaneous determination of linezolid and ciprofloxacin in human plasma from patients with hospital-acquired pneumonia

An ultra high-performance liquid chromatographic (UHPLC) method with PDA detection was developed and validated for the simultaneous quantification of linezolid and ciprofloxacin in human plasma and applied in hospital acquired pneumonia patients (HAP). The method uses a semi-automated microextraction by packed sorbent for sample preparation. All parameters in the extraction step (pH, sample volume, sample dilution and number of aspiration - ejection cycles) and in the desorption step (percentage of acetonitrile in the solvent of elution and number of aspirations of elution solvent through the device) were statistically significant when the recovery was used as response. The method showed good linearity with correlation coefficients, r²>0.9995 for the two drugs, as well as high precision (RSD%<9.77% in each case), accuracy ranged from -6.2% to +8.2. The limit of quantification of the two drugs was established at 0.01 and 0.02μg/mL for ciprofloxacin and linezolid, respectively. Linezolid, ciprofloxacin and internal standard were extracted from human plasma with a mean recovery ranging from 92.4% to 97.4%. During validation, the concentrations of linezolid and ciprofloxacin were found to be stable after 3 freeze-thaw cycles and for at least 24h after extraction. This method will subsequently be used to quantify the drugs dosage in patients with HAP to establish if the dosage regimen given is sufficient to eradicate the infection at the target site.

A simple high-performance liquid chromatography for the determination of linezolid in human plasma and saliva

Linezolid is an antimicrobial agent for the treatment of multiresistant Gram-positive infections. A practical high-performance liquid chromatography method was developed for the determination of linezolid in human plasma and saliva. Linezolid and an internal standard (o-ethoxybenzamide) were extracted from plasma and saliva with ethyl acetate and analyzed on a Capcell Pak C18 MG column with UV detection at 254 nm. The calibration curve was linear through the range 0.5-50 µg/mL using a 200 μL sample volume. The intra- and interday precisions were all <6.44% for plasma and 5.60% for saliva. The accuracies ranged from 98.8 to 110% for both matrices. The mean recoveries of linezolid were 80.8% for plasma and 79.0% for saliva. This method was used to determine the plasma and saliva concentrations of linezolid in healthy volunteers who were orally administered a 600 mg dose of linezolid. Our liquid-liquid extraction procedure is easy and requires a small volume of plasma or saliva (200 μL). This small volume can be advantageous in clinical pharmacokinetic studies, especially if children participate.

Validation of a new HPLC-UV method for determination of the antibiotic linezolid in human plasma and in bronchoalveolar lavage

A rapid and selective HPLC-UV method was developed for the quantification of linezolid (LNZ) in human plasma and bronchoalveolar lavage (BAL) at the concentrations associated with therapy. Plasma samples were extracted by solid-phase extraction followed by evaporation to dryness and reconstitution in mobile phase solution. The chromatographic separation was carried out on a C18 column with an isocratic mobile phase consisting of dihydrogen phosphate buffer 50 mm (pH 3.5) and acetonitrile (60:40 v/v). The detection was performed using a photodiode array. Under these conditions, a single chromatographic run could be completed within 12 min. The method was validated by estimating the precision and the accuracy for inter- and intra-day analysis in the concentration range of 25-25600 ng/mL. The method was linear over the investigated range with all the correlation coefficients R > 0.999. The intra- and inter-day precision was within 8.90% and the accuracy ranged from -4.76 to +5.20%. This rapid and sensitive method was fully validated and could be applied to pharmacokinetic study for the determination of LNZ levels in human plasma and BAL samples.