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Bioavailability and tolerability of nebulised dexamethasone sodium phosphate in adult horses
Author(s) -
Haspel A. D.,
Giguère S.,
Hart K. A.,
Berghaus L. J.,
Davis J. L.
Publication year - 2018
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/evj.12724
Subject(s) - tolerability , bioavailability , dexamethasone sodium phosphate , dexamethasone , pharmacology , phosphate , sodium , horse , medicine , chemistry , endocrinology , adverse effect , biology , biochemistry , paleontology , organic chemistry
Summary Background Nebulisation of the injectable dexamethasone sodium phosphate ( DSP ) would offer an inexpensive way of delivering a potent corticosteroid directly to the lungs of horses with asthma. However, this approach would be advantageous only if systemic absorption is minimal and if the preservatives present in the formulation do not induce airway inflammation. Objective To investigate the bioavailability of nebulised DSP and determine whether it induces airway inflammation or hypothalamic‐pituitary‐adrenal ( HPA ) axis suppression in healthy adult horses. Study design Randomised crossover experiment. Methods Dexamethasone sodium phosphate was administered to six healthy adult horses at a dose of 5 mg q. 24 h for 5 days via nebulised, or intravenous (i.v.) routes. Plasma dexamethasone concentrations were measured by UPLC / MS ‐ MS to calculate bioavailability. Cytological examination of bronchoalveolar fluid was performed at baseline and after the last dose of DSP . A validated chemiluminescent immunoassay was used to measure basal serum cortisol concentrations. Results After nebulisation to adult horses, dexamethasone had a mean (±s.d.) maximum plasma concentration of 0.774 ± 0.215 ng/mL and systemic bioavailability of 4.3 ± 1.2%. Regardless of route of administration, there was a significant decrease in the percentage of neutrophils in bronchoalveolar lavage fluid over time. During i.v. administration, basal serum cortisol concentration decreased significantly from baseline to Day 3 and remained low on Day 5. In contrast, basal serum cortisol concentration did not change significantly during administration via nebulisation. Main limitations Small sample size and short period of drug administration. Conclusions Dexamethasone sodium phosphate administered via nebulisation had minimal systemic bioavailability and did not induce lower airway inflammation or HPA axis suppression in healthy horses.