Short-term stability of atenolol in oral liquid formulations

The objective of this study was to determine the stability of atenolol in extemporaneously compounded liquid formulations. Two sets of formulations were prepared using either pure atenolol powder or atenolol tablets. Vehicles used for preparation were simple syrup, a methylcellulose-based vehicle, Ora-Sweet, Ora-Plus, and Ora-Sweet SF. The concentration of atenolol in the formulations was 2 mg/mL. Samples were collected at regular time intervals over a period of three months, and atenolol concentration was determined using a stability-indicating, high-performance liquid chromatography (HPLC) assay. All formulations were also visually observed for signs of settling. The HPLC results showed that all formulations prepared using the methylcellulose-based vehicle and Ora-Sweet SF were stable (ie, greater than 90% of atenolol remained unchanged) for more than 28 days. On the other hand, formulations prepared with simple syrup and Ora-Sweet were stable only for 14 days. Formulations prepared using simple syrup and Ora-Sweet as vehicles were also placed at elevated temperatures in order to study the effect of temperature on the stability of atenolol. The concentration of atenolol that remained unchanged depended on the vehicle used and the temperature at which the formulations were stored.