Theophylline does not potentiate the effects of a low dose of dexamethasone in horses with recurrent airway obstruction.
BACKGROUND
Theophylline has been shown to have corticosteroid-sparing effects for the treatment of human asthma. A similar effect, if present in horses, would allow diminishing the dose of corticosteroids administered to equine patients with inflammatory airway diseases.


OBJECTIVE
To evaluate whether theophylline potentiates the effects of a low dose of dexamethasone when treating horses with recurrent airway obstruction (RAO).


OBJECTIVE
Theophylline has steroid-sparing effects in horses with RAO.


METHODS
Ten mature mixed breed horses in clinical exacerbation of RAO were studied. Using an incomplete crossover design and 3 experimental periods of 7 days duration, horses were distributed randomly in 5 treatment groups; and administered dexamethasone s.i.d., at either 0.05 mg/kg bwt i.v. or per os, or 0.02 mg/kg bwt alone or combined with theophylline at 5 mg/kg bwt per os b.i.d. A fifth group was treated with theophylline alone at the above dosage. Lung function was evaluated prior to drug administration and then 3 and 7 days later.


RESULTS
Oral administration of dexamethasone alone or combined with theophylline failed to improve lung function significantly in RAO affected horses. Theophylline alone also failed to improve lung function in all treated horses. Conversely, dexamethasone administration at 0.05 mg/kg bwt i.v. resulted in a significant improvement in lung function starting on Day 3.


CONCLUSIONS
Oral theophylline for 7 days did not improve the effects of a low dose of dexamethasone for the treatment of horses with RAO.
Cesarini
C
C
Département des Sciences Cliniques, Faculté de Médecine Vétérinaire, Université de Montréal, CP 5000, Saint-Hyacinthe, Québec J2S7C6, Canada.
Hamilton
E
E
Picandet
V
V
Lavoie
J P
JP
D000284:Administration, Oral; D000818:Animals; D001993:Bronchodilator Agents / Q000627:therapeutic use*; D018592:Cross-Over Studies; D003907:Dexamethasone / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D005260:Female; D005938:Glucocorticoids / Q000627:therapeutic use*; D006734:Horse Diseases / Q000188:drug therapy*; D006736:Horses; D007275:Injections, Intravenous / Q000662:veterinary; D008173:Lung Diseases, Obstructive / Q000188:drug therapy / Q000662:veterinary*; D008297:Male; D012008:Recurrence; D013806:Theophylline / Q000627:therapeutic use*; D013997:Time Factors; D016896:Treatment Outcome
D001993:Bronchodilator Agents; D005938:Glucocorticoids; D003907:Dexamethasone; D013806:Theophylline