The effect of topical lidocaine on intradermal testing in atopic dogs

Background: Intradermal testing (IDT) most often requires sedation. Topical lidocaine offers an adjunct or alternative to sedation. Hypothesis/Objectives: We hypothesized that topical lidocaine would significantly reduce reactions to intradermal injections and that atopic dogs treated with topical lidocaine would have similar results with IDT to atopic dogs tested without topical lidocaine. Animals: Fifteen client-owned atopic dogs. Methods: In Part I, a 5% lidocaine patch, 5% lidocaine cream and a control with no active ingredients were compared. The lowest pain score during intradermal injection was established in six atopic dogs. Fifteen atopic dogs were enrolled in Part II, and lidocaine cream (found to be most effective in Part 1) was applied randomly to a single side of the thorax. An IDT was performed on each side of the chest. Subjective and objective scores of the control and lidocaine treatment sides were compared 15 and 30 min post-injection. Results: The 5% lidocaine cream had the greatest reduction in pain score associated with intradermal injection. There were no significant differences in mean wheal diameter for any evaluated allergen at any time point between the control and lidocaine-treated sides. There was high agreement between the two groups when assessing the subjective score for all but one allergen. Conclusions and clinical importance: Topical lidocaine may be used as adjunctive analgesia during IDT with caution in interpretation of subjective house dust scoring. Lidocaine cream appeared to reduce pain score and may allow reduction in concurrent sedation.