Uptake of drugs from topically applied anti-inflammatory preparations applied to racing animals.

The research investigates whether drugs in topically applied anti-inflammatory preparations could enter the bloodstream of racing animals. It found that some substances from these products did indeed appear in the urine of dogs and horses after application, with different preparations affecting the rate of absorption.

Research Methodology

• The study used dogs and horses as subjects and applied three common nonsteroidal anti-inflammatory preparations topically.
• The substances tested were dimethylsulphoxide, phenylbutazone, its metabolites, and lignocaine. These were monitored in the blood and urine of the animals.
• A gas chromatograph with a flame photometric detector was used to analyse the presence of dimethylsulphoxide.
• A gas chromatograph with a mass selective detector was used to analyse phenylbutazone, its metabolites, and lignocaine.

Research Findings

• Dimethylsulphoxide, phenylbutazone, and lignocaine were identified in the urine of dogs following multiple applications of the anti-inflammatory preparations.
• The amount of dimethylsulphoxide found in dog urine was proportionate to the amount present in the preparation applied.
• Phenylbutazone penetrated the skin more effectively from a cream-based preparation than from a solution or gel. This absorption wasn’t impacted by the concentration of dimethylsulphoxide.

Conclusions

• The study concluded that the superior skin penetration of phenylbutazone from cream preparations could be due to its presence as a neutral molecule in a hydrophobic medium.
• The researchers suggest that phenylbutazone penetrates the skin of dogs most effectively via a hydrophobic lipid route. This mechanism is likely distinct from the pathway used by dimethylsulphoxide to penetrate the skin.

By understanding the pathways and mechanisms of topical drug absorption, better monitoring and regulation strategies could be set up for the use of such preparations in racing animals. This could help prevent the misuse of performance-enhancing substances.