Severe equine asthma (recurrent airway obstruction) in exacerbation: inhaled corticosteroids vs systemic dexamethasone — MAYBE (weak evidence)

In horses with severe equine asthma (recurrent airway obstruction) in exacerbation, how do inhaled corticosteroids compare with systemic dexamethasone for improving lung function?

Shelf #365 · gate-verified and approved by the developer

MAYBE (weak evidence): In tiny crossover experiments (6 and 7 horses with hay-induced exacerbation), inhaled corticosteroids improved lung function, but the two carded trials disagree on how inhaled therapy compares with systemic dexamethasone: Rush 1998 found the response to aerosolized beclomethasone generally less marked than the response to parenterally administered dexamethasone, while Couëtil 2006 found low-dose inhaled beclomethasone significantly better than placebo and than a single intramuscular injection of dexamethasone 21-isonicotinate — a much weaker systemic comparator than a dexamethasone course. The larger randomised trial of inhaled fluticasone against oral prednisone and environmental management (Couëtil 2005) could not be carded in this build because its PubMed record could not be fetched and verified at drafting, so it contributes nothing to this stamp. Gaps: no carded field trial in client-owned horses, no comparison with oral prednisolone (the systemic corticosteroid most used in practice), lung-function endpoints only rather than clinical outcomes, and total carded numbers of 13 horses. Drafted Nov 10, 2026 (VetMed build, topic #365); all figures from abstracts fetched and verified at drafting.

Rush 1998: inhaled beclomethasone improved lung function, but the response was generally less marked than with parenteral dexamethasone (6 horses)

Randomized Controlled Trial and Clinical Trial (publication types); crossover and double-blind per the record's MeSH indexing (Cross-Over Studies, Double-Blind Method) — the abstract itself states only that horses were 'assigned to treatment groups'

Who: Horses: 6 horses with inducible and reversible recurrent airway obstruction (heaves) in an experimental setting (Kansas State University); episodes were induced by exposure (challenge) to moldy hay and straw for 7 days, and the horses were assigned across the treatment groups — aerosolized beclomethasone dipropionate, parenterally administered dexamethasone, and aerosolized propellant (control) — with maximal change in pleural pressure (ΔPplmax), pulmonary resistance (RL) and dynamic compliance (Cdyn) determined on days 0, 7, 10, 14 and 21.

Result: The RL and ΔPplmax were increased, and Cdyn was decreased, in all horses in response to natural challenge. Beclomethasone reduced RL on day 10, reduced ΔPplmax on days 14 and 21 and increased Cdyn on day 14. Dexamethasone reduced RL and ΔPplmax on days 10, 14, and 21 and increased Cdyn on days 10 and 14. Respiratory effort (subjective assessment) improved after 2 and 3 days of beclomethasone and dexamethasone administration respectively but rebounded to pretreatment values 1 and 3 days after discontinuation of the drugs. The authors concluded that the magnitude of response to aerosolized beclomethasone generally was less marked than the response to parenterally administered dexamethasone.

Watch out: Only 6 horses, in an induced-exacerbation experimental model, not field cases. The abstract does not state the drug doses or the dexamethasone route beyond 'parenteral', and does not itself use the words randomised, blinded or crossover — those design features rest on the record's publication types (Randomized Controlled Trial) and MeSH indexing (Cross-Over Studies, Double-Blind Method).

Rush BR, Raub ES, Rhoads WS, Flaminio MJ, Matson CJ, Hakala JE, Gillespie JR. Pulmonary function in horses with recurrent airway obstruction after aerosol and parenteral administration of beclomethasone dipropionate and dexamethasone, respectively. American Journal of Veterinary Research. 1998;59(8):1039-43. PMID: 9706210. Registry ID: none in the record. MeSH: Administration, Inhalation · Aerosols · Airway Obstruction/drug therapy · Airway Obstruction/physiopathology · Airway Obstruction/veterinary · Animal Feed · Animals · Anti-Inflammatory Agents/administration & dosage · Anti-Inflammatory Agents/therapeutic use · Beclomethasone/administration & dosage · Beclomethasone/therapeutic use · Cross-Over Studies · Dexamethasone/administration & dosage · Dexamethasone/therapeutic use · Double-Blind Method · Female · Food Microbiology · Horse Diseases/drug therapy · Horse Diseases/etiology · Horse Diseases/physiopathology · Horses · Injections, Intravenous · Male · Recurrence · Respiration/drug effects · Respiration/physiology · Respiratory Function Tests/veterinary

Couëtil 2006: low-dose inhaled beclomethasone improved lung function more than a single IM injection of dexamethasone isonicotinate or placebo (7 horses)

Randomized Controlled Trial (publication type); crossover design stated in the abstract — blinding is not stated in the record

Who: Horses: 7 horses with recurrent airway obstruction in an experimental setting (University of Liège); the horses were exposed to moldy hay until they developed airway obstruction on 3 separate occasions, and in a crossover design they were then treated with a placebo (injection on day 1), inhaled beclomethasone dipropionate (500 µg q12h for 10 days), or dexamethasone 21-isonicotinate (0.06 mg/kg, IM on day 1) and monitored for 10 days, with pulmonary function, bronchoalveolar lavage fluid cytology and transcription-factor activity measured before (day 1) and after treatment (day 10).

Result: Treatment with beclomethasone resulted in significantly improved pulmonary function of RAO-affected horses compared with placebo and dexamethasone treatments. However, none of the treatments had an effect on bronchoalveolar lavage fluid cytology or NF-kappaB and AP-1 activity in bronchial brushing cells: the benefits of low-dose inhaled beclomethasone on pulmonary function were not accompanied by a decrease in airway inflammatory cells or a suppression of transcription factors NF-kappaB and AP-1 DNA-binding activity.

Watch out: Only 7 horses. The systemic comparator is a single intramuscular injection of the long-acting ester dexamethasone 21-isonicotinate — not a course of dexamethasone — so this trial does not test inhaled therapy against standard repeated systemic dexamethasone. Blinding is not stated in the record and is not claimed here.

Couëtil LL, Art T, de Moffarts B, Becker M, Mélotte D, Jaspar F, Bureau F, Lekeux P. Effect of beclomethasone dipropionate and dexamethasone isonicotinate on lung function, bronchoalveolar lavage fluid cytology, and transcription factor expression in airways of horses with recurrent airway obstruction. Journal of Veterinary Internal Medicine. 2006;20(2):399-406. PMID: 16594601. Registry ID: none in the record. MeSH: Animals · Anti-Inflammatory Agents/therapeutic use · Beclomethasone/pharmacology · Beclomethasone/therapeutic use · Bronchoalveolar Lavage Fluid/cytology · Cross-Over Studies · Dexamethasone Isonicotinate/pharmacology · Dexamethasone Isonicotinate/therapeutic use · Female · Gene Expression Regulation/drug effects · Horse Diseases/drug therapy · Horses · Lung/drug effects · Lung/physiopathology · Lung Diseases, Obstructive/drug therapy · Lung Diseases, Obstructive/veterinary · Male · Respiratory Therapy · Transcription Factors/metabolism

Synthesis: inhaled corticosteroids improve lung function in exacerbation, but the two carded trials point in opposite directions against systemic dexamethasone

Synthesis

Who: Synthesis of the cards above: Rush 1998 (6 horses, crossover per record indexing, induced exacerbation, aerosolized beclomethasone vs parenteral dexamethasone vs aerosolized propellant control) and Couëtil 2006 (7 horses, crossover, induced obstruction, inhaled beclomethasone 500 µg q12h for 10 days vs single IM dexamethasone 21-isonicotinate vs placebo injection) — both small experimental studies.

Result: (1) Both trials found that an inhaled corticosteroid improved pulmonary function during induced exacerbation. (2) They point in opposite directions on the head-to-head question: against parenteral dexamethasone given over days, the inhaled drug's response was generally less marked (Rush); against a single injection of a long-acting dexamethasone ester, low-dose inhaled beclomethasone was significantly better than both placebo and the injection (Couëtil). (3) In Couëtil 2006 the lung-function gain came with no change in bronchoalveolar lavage cytology, so improved mechanics did not mean resolved airway inflammation.

Watch out: The two systemic comparators are not the same treatment: repeated parenteral dexamethasone (Rush) versus one injection of dexamethasone 21-isonicotinate (Couëtil). No carded trial compares inhaled corticosteroids with oral prednisolone, and none is a field trial in client-owned horses, so these results should not be silently transported to practice cases.

Synthesis of Rush BR et al. PMID: 9706210; Couëtil LL et al. PMID: 16594601. Registry IDs as on the individual cards.

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