Short-Term Stability Study of Doxycycline Tablets by High Performance Liquid Chromatography, Spectrophotometry in the Ultraviolet Region and Turbidimetry

Abstract

Doxycycline, an antimicrobial, is available for free in the Brazilian Public System under medical prescription. Therefore, the population have easy access to it. Regarding quality control, doxycycline stability studies are important due to the epimerization reactions and the formation of degradation products under conditions that are not favourable to the drug leading to severe damages to the patient. So, the aim of this study was to develop a short-term stability study of doxycycline hyclate in intact tablet, pulverized tablets and in raw material. It utilized spectrophotometry in the Ultraviolet Region (UV), High Performance Liquid Chromatography (HPLC) and microbiologic method of turbidimetry. The combination of physicochemical and microbiological techniques is important in the sense that it is not enough only to identify and quantify the drug, but also to verify the activity. The short-term stability study proved that doxycycline hyclate in raw material, intact tablet and pulverized tablets was unstable under extreme conditions of heat and humidity 40ºC ± 2.0ºC and 75% ± 5.0%. The results were significantly different at time 0 and time 6. Raw material followed order zero degradation equations for spectrophotometry and HPLC and second order equation for turbidimetry. Intact tablet and pulverized tablets followed order zero equations for HPLC and second order equation for spectrophotometry and turbidimetry. There was a decrease in the antimicrobial activity and possible formation of degradation products that were detected at the final time of the study. The method can also be used in the test routine of pharmaceutical quality control for the efficacy and reliability of doxycycline tablets.