Pergolide mesylate (proprietary name Permax) is used to treat equine Cushing's syndrome. Since pergolide mesylate has been removed from the market, the tablets are no longer available. Therefore, pergolide mesylate preparations have to be compounded for veterinary use. Compounded oral liquid formulations have been given arbitrary beyond-use dates of 14 days (aqueous) to 90 days (oil based). The goal of this study was to determine the stability of a 0.2 mg/mL pergolide oral liquid prepared according to a previousy published formulation and stored at room temperature. The sample preparation and the high-performance liquid chromatographic assay described in the United States Pharmacopeia-National Formulary were modified to treat the oral liquid as a suspension. The assay was evaluated prior to its use. A linear relationship was found between peak area and concentration with Rsquared values ranging for 0.989 to 0.999 for three of the sample calibration plots. The daily reproducibility and day-to-day variability of single injections of the assay were found to have relative standard deviations of 1.26% and 3.52%, respectively. Analysis of the oral liquid and a blank oral liquid (without pergolide mesylate) exposed to acid and heat demonstrated that the excipients and degradation species did not interfere with the drug peak. Samples, in replicates of five, were stored at room temperature, then pulled at specific intervals (1, 2, 4, 8, 12, and 16 weeks) and stored at -80 deg C for assay at a later date. After 16 weeks at room temperature, the drug degraded to 71% of its original concentration. The time to reach 90% potency (t90) of pergolide mesylate was calculated to be 6.5 weeks (45 days). Degradation studies at 35 deg C, 45 deg C, and 60 deg C are in progress.

Shank, B. R., & Ofner III, C. M. (2009). Stability of Pergolide Mesylate Oral Liquid at Room Temperature. International journal of pharmaceutical compounding, 13(3), 254.

Results indicated that pergolide mesylate was unstable after compounding in an aqueous vehicle and that storage conditions had an effect on stability of the compounded formulation. Compounded pergolide formulations in aqueous vehicles should be stored in a dark container, protected from light, and refrigerated and should not be used >30 days after produced. Formulations that have undergone a color change should be considered unstable and discarded.

Davis, J. L., Kirk, L. M., Davidson, G. S., & Papich, M. G. (2009). Effects of compounding and storage conditions on stability of pergolide mesylate. Journal of the American Veterinary Medical Association, 234(3), 385-389.

In the past 15 years, clinical data of over 1,500 patients treated with pergolide mesylate have been published. Pergolide is a dopamine agonist with a potent stimulating effect on D2 and also on D1 receptors. This pharmacodynamic characteristic seems the most effective in increasing the motility in Parkinson's disease. Pergolide has been used almost exclusively as an adjunct to levodopa treatment. Its positive effects seems to be related to its long plasma half life, about 27 hours, and 5-6 hours of clinical activity; it has shown to be effective on all parkinsonian symptoms except for the reduction of postural reflexes, it reduces off periods and compared to bromocriptine, it considerably improves the activities of daily living. Adverse reactions are, for the most part, mild and reversible, they mostly include nausea and gastroenteric disturbances.

Pezzoli, G., Canesi, M., Pesenti, A., & Mariani, C. B. (1995). Pergolide mesylate in Parkinson's disease treatment. Journal of neural transmission. Supplementum, 45, 203-212.