Stability of clonidine suspension in oral plastic syringes

Abstract

The stability of clonidine suspensions stored at room temperature and under refrigeration for three months was evaluated. Oral suspensions of clonidine 0.01 mg/mL were prepared in Ora-Blend and stored in clear plastic syringes at 25 °C and 4 °C. Samples were collected from each syringe at the time of preparation, at weekly intervals for up to 28 days, and on days 42, 56, 77, and 91. Changes in color, taste, and pH, as well as visual evidence of precipitation, were used to determine physical compatibility. Immediately after the physical observations were made, 1.5-mL samples from each syringe were transferred to polypropylene freezer vials and stored at -85 °C until high-performance liquid chromatographic (HPLC) analysis. The samples were analyzed by a validated stability-indicating HPLC-ultraviolet-light detection method. Stability was defined as the retention of at least 90% of the initial clonidine concentration. The precision of the assay was evaluated by intraday and interday validation methods. Clonidine suspensions stored at 25 °C and 4 °C maintained 99.2% and 99.0% of the initial concentration for 91 days, respectively. No interfering peaks were generated by forced degradation of clonidine with heat, hydrochloric acid, sodium hydroxide, or hydrogen peroxide There were no notable changes in pH, and all samples remained physically unchanged during the study period. An extemporaneously prepared suspension of clonidine 0.01 mg/mL in Ora-Blend was stable for at least 91 days when stored in clear plastic syringes at either 25 °C or 4 °C.