UHPLC-MS/MS method for the determination of azithromycin in human plasma of pediatric patients

Population Pharmacokinetics and Individualized Medication of Azithromycin for Injection in Children Under 6 Years Old

Pharmacokinetic data for injectable azithromycin in children remain limited. This study aims to develop and validate a population pharmacokinetic model of azithromycin for injection in children under 6 years old and optimize its dosage regimen in this population. We prospectively enrolled patients under 6 years old who received azithromycin for injection at Beijing Friendship Hospital, Capital Medical University. Demographic information, clinical characteristics, and venous blood samples were collected in accordance with the research protocol. Azithromycin concentrations were determined using a validated UPLC-MS/MS method. The population pharmacokinetic model was structured using Phoenix NLME. The adequacy and robustness of the model was evaluated using VPC and bootstrap. We optimized azithromycin's dosing regimen for injection through Monte Carlo simulations. We included 254 plasma concentration data from 148 patients to establish the model. The clearance and volume were 1.27 L/h/kg and 45.6 L/kg, respectively. The covariates included were weight and age. VPC plots and nonparametric bootstrap showed that the final PPK model was reliable and robust. Based on Monte Carlo simulation, we derived a simple and practical dosing scheme. The results provided reference for individualized dosing in this population. The individualized dosing scheme based on Monte Carlo simulation can optimize clinical decision-making and guide personalized therapy.

Development and Validation of a New Reversed Phase HPLC Method for the Quantitation of Azithromycin and Rifampicin in a Capsule Formulation

This research aimed to develop a new method for simultaneously estimating the presence of azithromycin (AZT) and rifampicin (RIF) in a capsule formulation using reverse-phase high-performance liquid chromatography. The developed method utilized a Gemini column with a 60:40% v/v acetonitrile and potassium dihydrogen phosphate mobile phase, a flow rate of 1 mL/min, and an injection volume of 20 μL. The detection wavelengths of 210 and 254 nm for AZT and RIF, respectively, were used. Validation ensures specificity with a peak purity index > 0.99999 for AZT and >0.99995 for RIF, affirming unambiguous analyte detection. The system suitability test, within acceptable limits, validates method reliability. Linearity calibration curves (R2 = 0.998) cover a 25-150% target concentration range. Accuracy studies employing the standard addition method yield recovery values between 96.6 and 103.9% for both drugs, confirming method accuracy. Precision studies reveal % relative standard deviation values consistently below 2%, highlighting reproducibility. Robustness testing supports method reliability under varying conditions. Application to a pharmaceutical capsule formulation demonstrates the method's practicality, accurately quantifying AZT (98.30%) and RIF (99.37%). This study provides a validated analytical approach for simultaneous quantification in commercial pharmaceutical products containing both drugs, enhancing pharmaceutical quality control for critical antibiotics in complex formulations.