Development and validation of stability indicating rp-hplc method for simultaneous determination of doxycycline and rifampicin in polymeric nanoparticles

The combination of doxycycline (DOXY) and rifampicin (RIF) is recommended as a treatment therapy for brucellosis by the World Health Organization. The aim of the current study was the development and validation of the stability-indicating reverse-phase high-performance liquid chromatography (RP-HPLC) method for the analysis of a combination of doxycycline & rifampicin. RP-HPLC method was developed and validated for the estimation of doxycycline and rifampicin combination as per ICH guidelines. The drug combination solution was exposed to different stress conditions viz. acidic, basic, photo-oxidation, and oxidation. The method was found linear in the range of 2 -10μg/mL for both the drugs with a retention time of 3.5 min for doxycycline and 6.5 min for rifampicin at lambda maximum of 350 nm. The RP-HPLC method was found precise and accurate with %RSD < 2%. The intra-day and inter-day precision were calculated and found within the acceptable range of 5%. Both drugs demonstrated good stability in the mobile phase after 6h. The LOD and LOQ of doxycycline and rifampicin were found 100 ng/mL & 200ng/mL and 150ng/mL & 500ng/mL, respectively. The forced degradation of the combination of drug solutions was performed. The degraded drug peaks were well-resolved from the peaks of drugs. The percentage encapsulation efficiency of doxycycline and rifampicin in nanoparticle system was assessed by utilizing the validated RP-HPLC method and found >60% (DOXY) and >70% (RIF). The developed RP-HPLC method of DOXY-RIF combination was rapid, accurate, precise, and stability-indicating. The method can be suitably applied for the determination of drugs in the nanoparticulate system.