Stability Determination of an Extemporaneously Compounded Ambrisentan Suspension by High Performance Liquid...

Ambrisentan, an endothelin receptor antagonist FDA-approved for the treatment of pulmonary arterial hypertension in adult patients, lacks an acceptable pediatric dosage form. The objective of this investigation was to determine the stability of an extemporaneously compounded ambrisentan suspension.

Ambrisentan suspension was compounded to a concentration of 1 mg/mL using commercially available suspending agents. The suspension was then evenly split into 2 plastic amber prescription bottles. One bottle was stored at room temperature and under continuous fluorescent light while the other bottle was stored under refrigeration and protection from light. A fast and selective reversed-phase high-performance liquid chromatography (HPLC) method was developed and validated for the analysis of ambrisentan. HPLC analysis was performed on samples withdrawn from the stock bottles at predetermined time intervals, up to 90 days.

The developed HPLC method enabled the elution and detection of ambrisentan peak at 4.4 minutes. HPLC analysis revealed that all samples from both storage conditions retained >90% potency throughout the study timeframe. There were no signs of any ambrisentan breakdown products on HPLC analysis. Color and odor of the final product was also consistent throughout the 90-day storage period.

Ambrisentan suspension, compounded to 1 mg/mL, is stable at room temperature or under refrigeration for up to 90 days.