Bioavailability of phenylbutazone preparations in the horse.

This research investigates the bioavailability of different formulations (paste and powder forms) of the drug phenylbutazone in horses and how it is affected by the horse’s eating habits. The results indicate that while there is a high variability among individual horses, phenylbutazone seems to be almost entirely absorbed when given as a paste before a meal or a powder mixed with a small bran mash. However, when administered after a meal or with full feed, phenylbutazone’s absorption appears to be less effective.

Study Approach

• The study was focused on comparing the absorption levels of phenylbutazone, an anti-inflammatory medication commonly used in horses, when given in different forms and under different feeding conditions.
• The experiment was carried out on six horses, which were given the drug intravenously and orally in both paste and powder forms.
• In an effort to study the potential impact of feeding on drug absorption, the paste form of the drug was given to horses before and after eating. The powder form was mixed into a small bran mash and a full feed (lucerne chaff, wheaten chaff and bran).

Key Findings

• The bioavailability of phenylbutazone administered in paste form before a meal and in powder form mixed with a small bran mash was found to be almost complete, despite considerable variability among horses.
• The study results indicate that the state of the stomach (empty or full) does have an effect on the absorption of the drug phenylbutazone. A lower peak plasma level of the drug was observed when it was administered after a meal or mixed with full feed, suggesting an inferior absorption outcome in comparison to administration on an empty or relatively empty stomach.

Implications

• The findings of this study suggest that for optimal absorption rates, phenylbutazone should ideally be given as a paste before a meal or as a powder in a small bran mash.
• Further understanding of the relationship between feeding habits and drug absorption can help in designing more effective drug administration protocols for horses, improving outcomes in disease management.