Stability test of metformin hydrochloride in human plasma using HPLC-UV for the protocol of therapeutic drug monitoring of metformin

摘要

Metformin accumulation not only indicates a significant pharmacokinetic variability correlating with its glycemic response but also proves to be one of the factors of fatal lactic acidosis. Therefore, therapeutic drug monitoring (TDM) of metformin is required as an effort to ascertain that metformin concentration is within the recommended therapeutic range. Metformin stability studies become an important part in TDM bioanalysis to provide accurate data of drug concentration for appropriate dose adjustments. This study aimed to conduct stability studies of metformin HCl in plasma samples by using HPLC with UV detector at 233 nm wavelength. Compound separation was carried out using the isocratic elution technique with the mobile phase consisting of acetonitrile: phosphate buffer 6 mM pH 5.2 (45: 55) and C_(18) column (4.6 mm × 150 mm, 5 μm) at a room temperature. The results showed that stock solution of metformin HCl was stable at 25°C and 4°C storage temperatures for 6 hours and 30 days, respectively. Meanwhile, metformin HCl in the plasma matrix was stable at 25°C storage temperature for 6 hours and for 1 day if stored at -20°C. This study recommended storing patients' plasma samples at -20°C for 24 hours during TDM of metformin.