Azitromicina: desenvolvimento e validação de métodos de análise em formas farmacêuticas

Abstract

Azithromycin (AZ) is a macrolide antibiotic derivate from erytromycin. AZ has a broad spectrum of activity against common gram-negative pathogens and has been used for the treatment of respiratory tract infection, skin infections and sexually transmitted diseases. In the Brazilian market AZ is available as tablets, compounded capsules and powder for oral suspension. The official methods for the assay of AZ in bulk form; capsules and powder for oral suspension are high performance liquid chromatography or microbiological diffusion assay. No monographs are reported in the pharmacopoeias for AZ evaluation in tablets. In this work two spectrophotometric methods were developed and validated for AZ analysis in tablets and powder for oral suspension. The first method was based on the reaction of AZ with concentrated sulfuric acid (98 % w/v), with detection at 226 nm. The other method was based in the charge-transfer reaction of the drug with s-acceptor iodine, with detection at 363 nm. Both methods showed good linearity (r>0.99), precision (CV<5%) and accuracy (>99%). The results obtained with the proposed methods were in good agreement with those obtained by microbiological diffusion agar method. The optimization of dissolution test conditions for in vitro quality control of AZ in tablets was also studied. The use of 900 mL of 0.1N HCl at 37.0 ± 0.5 ºC, paddle as apparatus, at a stirring rate of 50 rpm, provided satisfactory results for tested products. The percent dissolution of AZ in the established condition was more than 90% in 45 minutes. The validated spectrophotometric method used to evaluate the dissolution testing showed to be specific (with no interference of the placebo or tablets in the quantification of AZ), linear (r>0.99), precise (RSD<5%) and accurate (>97%). The drug showed satisfactory stability in the selected dissolution medium