Efficacy of Inhaled Levalbuterol Compared to Albuterol in Horses with Recurrent Airway Obstruction.

BACKGROUND: The (R)-enantiomer of racemic albuterol (levalbuterol) has bronchodilatory properties whereas the (S)-enantiomer causes adverse effects in human airways, animal models, and isolated equine bronchi. Levalbuterol is commercially available and improves pulmonary function of asthmatic patients with a longer duration of effect than albuterol. OBJECTIVE: To determine the dose at which inhaled levalbuterol produces maximal bronchodilatory effect (EDmax) and determine its duration of action in recurrent airway obstruction (RAO)-affected horses in comparison to racemic albuterol. ANIMALS: Nine horses with inducible and reversible RAO. METHODS: Randomized, crossover trial. Horses were challenged with moldy hay to induce airway obstruction. Horses were treated with nebulized albuterol or levalbuterol chosen randomly. Pulmonary function testing (PFT) was measured before and for up to 3 hours after bronchodilatation challenge. Maximum change in transpulmonary pressure (DPmax ) was measured to assess the dose effect and duration of action of each drug. After a 24 hours washout period, the bronchodilatation challenge was repeated with the second bronchodilator. RESULTS: The duration of effect was 60 minutes for albuterol and 120 minutes for levalbuterol. The dose of bronchodilator EDmax was not significantly different between albuterol and levalbuterol (EDmax = 125.0 [125-125 µg] and EDmax = 188 [125-188 µg] respectively; P = .068). The magnitude of bronchodilatation was not significantly different between the 2 treatments (61.1 and 59.9% decrease in DPmax for albuterol and levalbuterol respectively; P = .86). CONCLUSIONS AND CLINICAL IMPORTANCE: Levalbuterol is as effective a bronchodilator as albuterol; although levalbuterol lasts twice as long as albuterol, its duration of action is still too short to make it practical for RAO treatment.

Omega-3 fatty acid supplementation provides an additional benefit to a low-dust diet in the management of horses with chronic lower airway inflammatory disease.

BACKGROUND: Omega-3 polyunsaturated fatty acid (PUFA) may benefit humans and animals with chronic inflammatory diseases. HYPOTHESIS: Omega-3 PUFA supplementation improves clinical signs, lung function, and airway inflammation in horses with recurrent airway obstruction (RAO) and inflammatory airway disease (IAD). ANIMALS: Eight research horses and 35 client-owned horses. METHODS: A pilot study examined the dose of PUFA that can alter plasma PUFA composition. Then, a randomized, controlled clinical trial was performed in horses with RAO and IAD. Horses were fed a complete pelleted diet with no hay and randomly assigned to 1 of 3 daily treatments for 2 months: 30 or 60 g of the supplement or 30 g of placebo. Clinical signs, lung function, plasma PUFA composition, and bronchoalveolar lavage fluid (BALF) cytology were evaluated. Data were expressed as median (25-75th percentiles). P < .05 was considered significant. RESULTS: Polyunsaturated fatty acid supplementation resulted in increased plasma docosahexaenoic acid (DHA) that peaked at 4 weeks. Clinical improvement was noted in all horses involved in the clinical trial, but the group that received PUFA had greater improvement in clinical signs (cough score improved 60%), lung function (respiratory effort decreased 48%), and BALF (neutrophils decreased from 23 to 9%) when compared to placebo (cough score improved 33%, respiratory effort decreased 27%, BALF neutrophils increased from 11 to 17%; P < .05). CONCLUSIONS AND CLINICAL IMPORTANCE: Feeding horses with RAO and IAD a PUFA supplement containing 1.5-3 g DHA for 2 months provides an additional benefit to low-dust diet.

Effects of N-butylscopolammonium bromide on lung function in horses with recurrent airway obstruction.

BACKGROUND: Equine recurrent airway obstruction (RAO) is characterized by airway inflammation, bronchoconstriction, and increased mucus production in the airways. Anticholinergic drugs like atropine induce bronchodilatation and rapid improvement in lung function. N-butylscopolammonium bromide (NBB) is an anticholinergic drug used to relieve spasmodic colic in horses, but its effect on airway smooth muscle is unknown. OBJECTIVE: To evaluate the effect of NBB on clinical signs and lung function of RAO-affected horses. ANIMALS: Nine horses diagnosed with RAO. METHODS: Double-blind, placebo-controlled, randomized crossover trial. Horses were challenged with moldy hay until a maximum change in transpulmonary pressure (∆P(L) (max) ) > 15 cm H(2) O was achieved. NBB (0.3 mg/kg) or placebo (0.9% saline) was administered IV. Clinical scores and lung function were recorded at baseline and then periodically after treatment administration. Horses were allowed a 6-week washout before administration of opposite treatments. RESULTS: Clinical score at 10 and 30 minutes (8.7 ± 2.8 and 8.7 ± 3.2, respectively) after NBB administration was significantly lower than baseline (10.8 ± 2.4). NBB administration resulted in a significant decrease in ∆P(L) (max) (baseline: 35.1 ± 6.9 cm H(2) O) starting 2 minutes after administration (16.3 ± 6.6 cmH(2) O) with a maximum decline observed at 10 minutes (13.5 ± 7.1 cm H(2) O). ∆P(L) (max) values between 60 and 120 minutes after NBB administration were not different from placebo. CONCLUSION AND CLINICAL IMPORTANCE: N-butylscopolammonium bromide is a potent bronchodilator, reaching maximum effect 10 minutes after intravenous administration. This effect dissipates within 1 hour of drug administration.

Evaluation of the field efficacy of an avirulent live Lawsonia intracellularis vaccine in foals.

Equine proliferative enteropathy caused by Lawsonia intracellularis is an emerging disease with as yet unaddressed preventative measures. The hypothesis of this study was that vaccination will prevent clinical and sub-clinical disease. Weanling Thoroughbreds (n=202) from Central Kentucky were randomly assigned into two groups (vaccinated and non-vaccinated). Vaccinated foals received 30 mL of an avirulent, live L. intracellularis vaccine intra-rectally twice, 30 days apart. Foals were monitored for clinical disease, total solids and average weight gain until yearling age. There was an overall decreased disease incidence on the farms involved in the study that did not differ significantly between the groups. This decreased disease prevalence in the study population may be associated with the ongoing vaccine trial on these farms, as disease prevalence in Central Kentucky did not change in 2009 compared to 2008.