Effect of elevated storage temperatures on the concentration of active ingredients in 5 commonly used large animal pharmaceuticals
Most veterinary pharmaceuticals are labeled to be stored at or below 77°F (25°C) or 86°F (30°C). Previous work showed that temperatures in ambulatory veterinary practice vehicles frequently exceeded those temperatures. The objective of this study was to determine the effect of higher storage temperatures on the active ingredient concentration of drugs commonly used in large animal practice. Five bottles of dino- prost, flunixin meglumine, gonadorelin, tulathromycin, and xylazine were maintained at room temperature (controls) and 5 additional bottles of each product were maintained in a programmable chamber set to mimic temperatures previously recorded in a veterinary practice vehicle. Samples were collected from all bottles on days 0,40,80, and 120, and were analyzed in duplicate by liquid chromatography/mass spectrometry. Changes in active ingredient concentration were assessed by linear regression, and t-tests were performed to compare slopes of time:concentration curves for control and treatment drugs. Slopes of drug concentrations over 120 days for all 5 drugs were less than 0.04, and there was no statistically significant difference between concentration slopes over time for control vs treatment bottles. No significant effect of elevated storage temperatures on product active ingredient was found in this study. However, due to the limited conditions of this study, practitioners are still advised to follow label recommendations when storing pharmaceuticals.