Clinical effects and pharmacokinetics of nebulized lidocaine in healthy horses.
Authors: Minuto Jillian, Bedenice Daniela, Ceresia Michelle, Zaghloul Iman, Böhlke Mark, Mazan Melissa R
Journal: Frontiers in veterinary science
Summary
# Clinical Effects and Pharmacokinetics of Nebulised Lidocaine in Healthy Horses Nebulised lidocaine holds potential as a corticosteroid-sparing treatment for equine asthma, yet its safety profile and pharmacokinetic behaviour remained uncharacterised until this 2022 study. Using six healthy horses, researchers administered 1 mg/kg of 4% preservative-free lidocaine via nebuliser (Flexineb®) and assessed upper airway sensitivity, lung mechanics, cellular airway response, and systemic absorption through endoscopy, bronchoalveolar lavage, pulmonary function testing, and blood/urine sampling at multiple timepoints. The drug achieved a mean epithelial lining fluid concentration of 9.63 ± 5.05 µg/mL with 29.7% bioavailability, concentrating preferentially in the lower airway (CELF:Cmax plasma ratio of 64.4) and remaining detectable systemically for 24 hours and in urine for 48 hours; whilst upper airway reflexes remained intact and inflammatory markers unchanged, two additional horses showed hyperresponsiveness to histamine bronchoprovocation post-nebulisation despite absent clinical signs. For practitioners considering nebulised lidocaine as an adjunctive therapy, these findings provide reassurance regarding upper airway safety and demonstrate effective lower airway drug delivery, though the unexpected increase in airway reactivity—particularly in asthmatic populations—warrants cautious interpretation and necessitates further efficacy trials before widespread clinical adoption.
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Practical Takeaways
- •Nebulized lidocaine shows promise as a potential corticosteroid-sparing option for equine asthma with good local airway penetration and no observed safety concerns in healthy horses
- •Clinicians should be aware that while well-tolerated, some horses may develop increased airway reactivity to provocative stimuli post-nebulization, warranting further safety evaluation in asthmatic populations
- •Current evidence is limited to healthy horses; efficacy and safety must be confirmed in clinically affected asthmatic horses before clinical adoption
Key Findings
- •Nebulized lidocaine (1 mg/kg) achieved mean epithelial lining fluid concentration of 9.63 μg/mL with 29.7% bioavailability and remained detectable in serum for 24 hours and urine for 48 hours
- •Lidocaine concentrations were 64.4-fold higher in epithelial lining fluid than plasma (CELF:Cmax ratio), supporting local airway delivery
- •No adverse effects on upper airway sensitivity, laryngospasm, or BAL cytology were observed, but increased airway reactivity to histamine occurred in 2 additional horses post-nebulization
- •Baseline lung mechanics remained normal following nebulization, though lung resistance decreased post-treatment in the absence of clinical signs