Effects of dexamethasone and hydroxyzine treatment on intradermal testing and allergen-specific IgE serum testing results in horses.

The research aims to ascertain the impact of the drugs dexamethasone or hydroxyzine on allergen-specific IgE serum testing (ASIST) and intradermal testing (IDT) results for horses.

Overview of the Research

• The research intended to see if the administration of the drugs dexamethasone or hydroxyzine had a significant impact on ASIST and IDT results.
• The experiment was carried out on five horses that did not show any signs of atopic dermatitis.
• The IDT was done using saline, eight commercial extracts, and histamine, with the results being evaluated by comparison to saline and histamine scores, and via measurements of the diameter of the wheal (the swelling created by the test).

Administration of Dexamethasone and Testing

• Following baseline testing, each horse was given 20 mg of dexamethasone daily for 7 days via intramuscular injection.
• Tests were then done 3-4 hours after the last dose, then 7 days after, then 14 days after.

Administration of Hydroxyzine and Testing

• After the dexamethasone tests, 500 mg of hydroxyzine was administered orally twice daily for 7 days.
• Tests were performed 3-4 hours, 3 days, and 7 days after the last dose.

Observations and Conclusion

• By comparing pre- and post-treatment scores, no differences were found for IDT.
• However, the wheal diameter for the extracts decreased after the final dose of both medications.
• The diameter returned to pre-treatment levels within 14 days of discontinuing dexamethasone, and 7 days after discontinuing hydroxyzine.
• There were no significant changes found in the ASIST results.
• The study concluded that administering dexamethasone or hydroxyzine for 7 days doesn’t affect the ASIST results but does temporarily reduce the IDT wheal diameters.
• As per the findings of the study, it is recommended to wait 14 days after discontinuing dexamethasone and 7 days after hydroxyzine before performing IDT.