Stability of pergolide mesylate oral liquid at room temerature.

The research investigates the stability of Pergolide Mesylate oral liquid, a veterinary medication used for equine Cushing’s syndrome, stored at room temperature. It finds that after 16 weeks at room temperature, the drug degraded to 71% of its original concentration.

Research Motivation

• The study was initiated due to withdrawal of Pergolide Mesylate’s tablets from the market, making it necessary to compound oral liquid preparations for veterinary use.
• Given arbitrary beyond-use dates ranging from 14 to 90 days for such compounded preparations, the researchers wanted to definitively establish the stability of a 0.2 mg/mL Pergolide Mesylate oral liquid stored at room temperature.

Methodology

• The researchers prepared a 0.2 mg/mL Pergolide Mesylate oral liquid according to a previously published formulation.
• They used a modified version of the U.S. Pharmacopeia-National Formulary’s high-performance liquid chromatographic assay, treating the oral liquid as a suspension.
• The assay was thoroughly evaluated before commencement.
• The research team performed tests to find a linear relationship between peak area and concentration, checked on the reproducibility and day-to-day variability of the assay, and ensured that other elements did not interfere with the drug peak.

Sample Storage and Testing

• The samples, created in replicates of five, were stored at room temperature and taken out at specified intervals – 1, 2, 4, 8, 12, and 16 weeks – for later assay at -80 degrees Celsius.

Findings

• After 16 weeks at room temperature, the Pergolide Mesylate oral liquid was found to have degraded to 71% of its initial concentration.
• The amount of time for the drug to reach 90% potency (t90) was determined to be 6.5 weeks or 45 days.
• Currently, similar degradation studies at higher temperatures (35, 45, and 60 degrees Celsius) are being conducted.