Studies on a new paste preparation of phenylbutazone.

This study examines the absorption and bioavailability of a new paste form of phenylbutazone in ponies and thoroughbreds, revealing that despite showing higher bioavailability, the paste shows more toxicity in comparison to its powder form.

Study Overview

The research involved studying the absorption characteristics of a new paste preparation of phenylbutazone, a nonsteroidal anti-inflammatory drug often used in horses. They assessed this in two types of horses – ponies and thoroughbreds, considering factors such as bioavailability and possible toxic effects.

Methodology

• Phenylbutazone was administered in two forms – as a paste and as a powder – both at a dose rate of 5 mg/kg.
• The researchers used a multi-dose applicator for administering the paste but noted that they could not accurately control the dosage.
• To determine the effects of repeated use of the drug, the paste was given twice daily for a certain period of time and the reactions of the horses were observed and recorded.

Results

• The researchers found that although the paste had greater bioavailability (meaning a larger amount of the active substance was absorbed into the bloodstream), it also presented higher toxicity than the powder form.
• This was evidenced in both ponies and thoroughbreds, indicating that the type of horse did not significantly impact the results.
• Additional toxic effects that had not been previously reported were observed. These included neutropenia, a condition characterized by a low count of neutrophils, a type of white blood cell.
• In contrast, repeated intravenous administration of phenylbutazone at a dose of 3.3 mg/kg twice daily for eight days produced no adverse effects.

Conclusion

The results of this study suggest that although the paste form of phenylbutazone shows higher bioavailability, it also exhibits increased toxicity compared to the powder form. Therefore, while it may be absorbed more effectively into the bloodstream, the drawbacks in terms of possible health complications may outweigh the benefits in practical use. These findings underscore the importance of considering both efficacy and safety when developing new formulas of medicines.