Effects of inhaled beclomethasone dipropionate on respiratory function in horses with chronic obstructive pulmonary disease (COPD)

Inhalative Nanoparticulate CpG Immunotherapy in Severe Equine Asthma: An Innovative Therapeutic Concept and Potential Animal Model for Human Asthma Treatment

Simple Summary

Severe equine asthma is the most common globally widespread non-infectious equine respiratory disease (together with its mild and moderate form), which is associated with exposure to hay dust and mold spores, has certain similarities to human asthma, and continues to represent a therapeutic problem. Immunomodulatory DNA sequences (CpG) bound to nanoparticles were successfully administered by inhalation to severe asthmatic horses in several studies. It was possible to demonstrate a significant, sustained, one-to-eight-week improvement in important clinical parameters: partial oxygen pressure in the blood, quantity and viscosity of tracheal mucus secretion in the airways, and the amount of inflammatory cells in the respiratory tracts of severe asthmatic horses. The immunotherapy with CpG is performed independent of specific allergens. At an immunological level, the treatment leads to decreases in allergic and inflammatory parameters. This innovative therapeutic concept thus opens new perspectives in severe equine asthma treatment and possibly also in human asthma treatment.

Abstract

Severe equine asthma is the most common globally widespread non-infectious equine respiratory disease (together with its mild and moderate form), which is associated with exposure to hay dust and mold spores, has certain similarities to human asthma, and continues to represent a therapeutic problem. Immunomodulatory CpG-ODN, bound to gelatin nanoparticles as a drug delivery system, were successfully administered by inhalation to severe equine asthmatic patients in several studies. It was possible to demonstrate a significant, sustained, and allergen-independent one-to-eight-week improvement in key clinical parameters: the arterial partial pressure of oxygen, the quantity and viscosity of tracheal mucus, and neutrophilic inflammatory cells in the respiratory tracts of the severe equine asthmatic subjects. At the immunological level, an upregulation of the regulatory antiallergic and anti-inflammatory cytokine IL-10 as well as a downregulation of the proallergic IL-4 and proinflammatory IFN-γ in the respiratory tracts of the severe equine asthmatic patients were identified in the treatment groups. CD4⁺ T lymphocytes in the respiratory tracts of the asthmatic horses were demonstrated to downregulate the mRNA expression of Tbet and IL-8. Concentrations of matrix metalloproteinase-2 and -9 and tissue inhibitors of metalloproteinase-2 were significantly decreased directly after the treatment as well as six weeks post-treatment. This innovative therapeutic concept thus opens new perspectives in the treatment of severe equine asthma and possibly also that of human asthma.

[Remodeling in equine asthma - Effects of antigen avoidance and pharmacological therapy]

The term remodeling describes the process resulting in a tissue that is structurally and architecturally altered compared to its healthy counterpart. At least in severe equine asthma, this occurs mainly, but not exclusively, as a consequence of neutrophilic airway inflammation and is characterized by hypertrophy of the smooth muscle layers in airway and arterial walls as well as fibrosis of the bronchial walls and pulmonary interstitial tissue. To date, much less is known for mild to moderate equine asthma. For a long time it was assumed that these processes are irreversible, and at least for the remodeling of airway smooth muscle this is valid until today. In contrast, remodeling of the extracellular matrix disappears almost completely following long-term remission in consequence to strict antigen avoidance and environmental improvement as well as after glucocorticoid therapy. The remodeling of the arterial vasculature is also reversible following at least 12 months of antigen avoidance and bronchodilatory therapy, but not by inhaled glucocorticoids alone. Although not proven to date, the mild to moderate forms with a good prognosis for complete recovery may be a progenitor for severe equine asthma, in which lung function is restricted even during disease remission despite the absence of obvious clinical signs. Early diagnosis and therapy are, therefore, essential for the management of equine asthma prior to the development of irreversible remodeling, in particular of the bronchial smooth muscle. Antigen avoidance is of highest importance, and should be supported by glucocorticoids and bronchodilators.

Glucocorticoid treatment in horses with asthma: A narrative review

Despite substantial research efforts to improve the treatment and outcome of horses with asthma, glucocorticoids (GC) remain the cornerstone of drug treatment of this prevalent disease. The high efficacy of GC to relieve airway obstruction explains their extensive use despite potential deleterious effects. However, much is yet to be uncovered concerning GC use in horses with asthma, including the comparative efficacy of the different drugs, the determination of minimal effective doses and the mechanisms underlying their variable modulation of airway inflammation. The objectives of this structured review were to report and compare the plethora of effects of the various GC used in asthmatic horses with a focus on impact on lung function, airway inflammation, and bronchial remodeling. Adverse effects are also briefly described, with an emphasis on those that have been specifically reported in horses with asthma. Ultimately, we aimed to highlight gaps in the literature and to identify future research areas.

Effect of different doses of inhaled ciclesonide on lung function, clinical signs related to airflow limitation and serum cortisol levels in horses with experimentally induced mild to severe airway obstruction

Background

Inhaled corticosteroids are effective for the treatment of equine asthma but they induce cortisol suppression with potential side effects.

Objectives

To study the efficacy of ciclesonide, an inhaled corticosteroid with an improved safety profile, on lung function, clinical signs related to airway obstruction, and serum cortisol levels in asthmatic horses exposed to a mouldy hay challenge.

Study design

Cross‐over placebo controlled, blinded, randomised experiment.

Methods

Sixteen horses were enrolled in three subsequent dose‐titration studies (8 horses/study) to investigate the effects of inhaled ciclesonide administered for 2 weeks at doses ranging from 450 to 2700 μg twice daily or 3712.5 μg once daily. Systemic dexamethasone (0.066 mg/kg per os) was our positive control. A placebo group was also studied. Lung function and clinical scores were blindly performed before and after 7 and 14 days of treatment. Serum cortisol was measured before and after 3, 5, 7, 10, 14 days of treatment as well as 3 and 7 days post treatment.

Results

After 7 days, dexamethasone induced a significant reduction in pulmonary resistance (from 2.5 ± 0.6 at day 0 to 1.1 ± 0.7 cm H₂O/L/s), pulmonary elastance (5.0 ± 2.6 to 1.2 ± 1.0 cm H₂O/L), and of the weighted clinical score (14.8 ± 4.7 to 8.0 ± 4.4). Similarly, ciclesonide 1687.5 μg twice daily significantly improved pulmonary resistance (2.7 ± 1.1 to 1.6 ± 0.8 cm H₂O/L/s), pulmonary elastance (5.2 ± 3.1 to 2.2 ± 1.3 cm H₂O/L), and weighted clinical score (13 ± 2.9 to 10.8 ± 4.2). Serum cortisol suppression (<50 nmol/L) systematically occurred with dexamethasone from day 3 of treatment up to day 3 post treatment, but not with ciclesonide at any tested doses. Placebo did not exert any significant beneficial effect.

Main limitations

Experimentally induced asthma exacerbations in horses might respond differently to treatment than naturally occurring exacerbations.

Conclusions

Inhaled ciclesonide is an effective treatment for horses with equine asthma. Serum cortisol was unaffected by treatment.

Efficacy of inhaled budesonide for the treatment of severe equine asthma

Background

Corticosteroids are the most potent drugs for the control of severe equine asthma, but adverse effects limit their chronic systemic administration. Inhaled medications allow for drug delivery directly into the airways, reducing the harmful effects of these drugs.

Objectives

To evaluate the efficacy of inhaled budesonide specifically formulated for the equine use and administered by a novel inhalation device in horses with severe asthma.

Study design

Experimental studies in horses with naturally occurring asthma with cross‐over, randomised, blinded experimental designs.

Methods

In Study 1, budesonide (1800 μg twice daily) administered using a novel Respimat^® based inhaler was compared to i.v. dexamethasone (0.04 mg/kg). In Study 2, 3 doses of budesonide (450, 900, and 1800 μg) were compared to oral dexamethasone (0.066 mg/kg). Lung function, bronchoalveolar fluid cytology (Study 1), CBC, serum chemistry, and serum cortisol and adrenocorticotropic hormone (ACTH) values were evaluated.

Results

In Study 1, there was a marked and significant improvement in the lung function of all horses treated with budesonide and dexamethasone. Neutrophil percentages in bronchoalveolar fluid decreased in all horses treated with dexamethasone and in four of six horses treated with budesonide. Serum cortisol and blood ACTH concentrations decreased with both treatments. In Study 2, there was a significant improvement in the lung function with all dosages of budesonide, and the effects of higher dosages were comparable to those of dexamethasone. Dexamethasone and budesonide at the two higher dosages induced a significant decrease of cortisol concentrations.

Main limitations

The Respimat^® based inhaler is not currently commercially available.

Conclusions

Administration of budesonide with the Respimat^® based inhaler provided dose‐dependent relief of airway obstruction in horses with severe asthma, but also a suppression of serum cortisol.

Bioavailability and tolerability of nebulised dexamethasone sodium phosphate in adult horses

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.

Inhalation Therapy in Horses

This article discusses the benefits and limitations of inhalation therapy in horses. Inhalation drug therapy delivers the drug directly to the airways, thereby achieving maximal drug concentrations at the target site. Inhalation therapy has the additional advantage of decreasing systemic side effects. Inhalation therapy in horses is delivered by the use of nebulizers or pressured metered dose inhalers. It also requires the use of a muzzle or nasal mask in horses. Drugs most commonly delivered through inhalation drug therapy in horses include bronchodilators, antiinflammatories, and antimicrobials.

Pharmacological treatments in asthma-affected horses: A pair-wise and network meta-analysis

BACKGROUND

Equine asthma is a disease characterised by reversible airflow obstruction, bronchial hyper-responsiveness and airway inflammation following exposure of susceptible horses to specific airborne agents. Although clinical remission can be achieved in a low-airborne dust environment, repeated exacerbations may lead to irreversible airway remodelling. The available data on the pharmacotherapy of equine asthma result from several small studies, and no head-to-head clinical trials have been conducted among the available medications.

OBJECTIVES

To assess the impact of the pharmacological interventions in equine asthma and compare the effect of different classes of drugs on lung function.

STUDY DESIGN

Pair-wise and network meta-analysis.

METHODS

Literature searches for clinical trials on the pharmacotherapy of equine asthma were performed. The risk of publication bias was assessed by funnel plots and Egger's test. Changes in maximum transpulmonary or pleural pressure, pulmonary resistance and dynamic lung compliance vs. control were analysed via random-effects models and Bayesian networks.

RESULTS

The results obtained from 319 equine asthma-affected horses were extracted from 32 studies. Bronchodilators, corticosteroids and chromones improved maximum transpulmonary or pleural pressure (range: -8.0 to -21.4 cmH₂ O; P<0.001). Bronchodilators, corticosteroids and furosemide reduced pulmonary resistance (range: -1.2 to -1.9 cmH₂ O/L/s; P<0.001), and weakly increased dynamic lung compliance. Inhaled β₂ -adrenoreceptor (β₂ -AR) agonists and inhaled corticosteroids had the highest probability of being the best therapies. Long-term treatments were more effective than short-term treatments.

MAIN LIMITATIONS

Weak publication bias was detected.

CONCLUSIONS

This study demonstrates that long-term treatments with inhaled corticosteroids and long-acting β₂ -AR agonists may represent the first choice for treating equine asthma. Further high quality clinical trials are needed to clarify whether inhaled bronchodilators should be preferred to inhaled corticosteroids or vice versa, and to investigate the potential superiority of combination therapy in equine asthma.

Inflammatory Airway Disease of Horses--Revised Consensus Statement

The purpose of this manuscript is to revise and update the previous consensus statement on inflammatory airway disease (IAD) in horses. Since 2007, a large number of scientific articles have been published on the topic and these new findings have led to a significant evolution of our understanding of IAD.

Recurrent airway obstruction: a review

Recurrent airway obstruction is a widely recognised airway disorder, characterised by hypersensitivity-mediated neutrophilic airway inflammation and lower airway obstruction in a subpopulation of horses when exposed to suboptimal environments high in airborne organic dust. Over the past decade, numerous studies have further advanced our understanding of different aspects of the disease. These include clarification of the important inhaled airborne agents responsible for disease induction, improving our understanding of the underlying genetic basis of disease susceptibility and unveiling the fundamental immunological mechanisms leading to establishment of the classic disease phenotype. This review, as well as giving a clinical overview of recurrent airway obstruction, summarises much of the work in these areas that have culminated in a more thorough understanding of this debilitating disease.

Non-genomic action of beclomethasone dipropionate on bronchoconstriction caused by leukotriene C4 in precision cut lung slices in the horse

BACKGROUND

Glucocorticoids have been proven to be effective in the therapy of recurrent airway obstruction (RAO) in horses via systemic as well as local (inhalative) administration. Elective analysis of the effects of this drug on bronchoconstriction in viable lung tissue offers an insight into the mechanism of action of the inflammatory cascade occurring during RAO which is still unclear. The mechanism of action of steroids in treatment of RAO is thought to be induced through classical genomic pathways. We aimed at electively studying the effects of the glucocorticoid beclomethasone dipropionate on equine precision-cut lung slices (PCLS).PCLS were used to analyze ex-vivo effects of beclomethasone on inhibiting bronchoconstriction in the horse. The inhibiting effect was measured through instillation of a known mediator of inflammation and bronchoconstriction, leukotriene C4. For this, the accessory lobes of 13 horses subjected to euthanasia for reasons unrelated to the respiratory apparatus were used to obtain viable lung slices.

RESULTS

After 30 minutes of PCLS incubation, beclomethasone showed to significantly inhibit the contraction of the bronchioles after instillation with leukotriene C4. The EC50 values of the two contraction curves (LTC4 with and without BDP) differed significantly from each other (p = 0.002). The possibility of a non-genomic rapid mechanism of action seems likely since transcriptional activities require a longer lag period.

CONCLUSIONS

In human neuroendocrinology, high levels of glucocorticoids have been proven to function via a non-genomic mechanism of membrane receptors. The concentration of beclomethasone used on the lung slices in our study can be considered as high. This allows speculation about similar rapid non-genomic mechanisms of high-dosage inhaled glucocorticoids in the lower airways of horses. However, further assessment on a molecular basis is needed to confirm this.

Heaves, an asthma-like disease of horses

Animal models have been developed to investigate specific components of asthmatic airway inflammation, hyper-responsiveness or remodelling. However, all of these aspects are rarely observed in the same animal. Heaves is a naturally occurring disease of horses that combines these features. It is characterized by stable dust-induced inflammation, bronchospasm and remodelling. The evaluation of horses during well-controlled natural antigen exposure and avoidance in experimental settings allows the study of disease mechanisms in the asymptomatic and symptomatic stages, an approach rarely feasible in humans. Also, the disease can be followed over several years to observe the cumulative effect of repeated episodes of clinical exacerbation or to evaluate long-term treatment, contrasting most murine asthma models. This model has shown complex gene and environment interactions, the involvement of both innate and adaptive responses to inflammation, and the contribution of bronchospasm and tissue remodelling to airway obstruction, all occurring in a natural setting. Similarities with the human asthmatic airways are well described and the model is currently being used to evaluate airway remodelling and its reversibility in ways that are not possible in people for ethical reasons. Tools including antibodies, recombinant proteins or gene arrays, as well as methods for sampling tissues and assessing lung function in the horse are constantly evolving to facilitate the study of this animal model. Research perspectives that can be relevant to asthma include the role of neutrophils in airway inflammation and their response to corticosteroids, systemic response to pulmonary inflammation, and maintaining athletic capacities with early intervention.

Effect of long-term fluticasone treatment on immune function in horses with heaves

BACKGROUND

Corticosteroids currently are the most effective pharmacological treatment available to control heaves in horses. Systemically administered corticosteroids have been shown to alter immune response in horses, humans, and other species. Aerosolized administration theoretically minimizes systemic adverse effects, but the effect of inhaled corticosteroids on immune function has not been evaluated in horses.

OBJECTIVES

To evaluate the effects of prolonged administration of inhaled fluticasone on the immune system of heaves-affected horses.

ANIMALS

Heaves-affected horses were treated with inhaled fluticasone (n = 5) for 11 months or received environmental modifications only (n = 5).

METHODS

Prospective analysis. Clinical parameters and CBC, lymphocyte subpopulations and function, and circulating neutrophil gene expression were sequentially measured. Primary and anamnestic immune responses also were evaluated by measuring antigen-specific antibodies in response to vaccination with bovine viral antigen and tetanus toxoid, respectively.

RESULTS

No clinical adverse effects were observed and no differences in immune function were detected between treated and untreated horses.

CONCLUSIONS AND CLINICAL IMPORTANCE

The treatment of heaves-affected horses with inhaled fluticasone at therapeutic dosages for 11 months has no significant detectable effect on innate and adaptive (both humoral and cell-mediated) immune parameters studied. These results suggest that prolonged administration of fluticasone would not compromise the systemic immune response to pathogens nor vaccination in adult horses.

Physiology of equine performance and associated tests of function

This review addresses the physiology of performance horses in the context of functional tests aimed at assisting clinicians in the search for explanations of the individual's limitations, actual or perceived as below expectation. The intention is to assist clinicians who are faced frequently by owners or trainers seeking explanations for poor performance; and for research workers as a basis on which to proceed in their search for new methodologies, particularly those that can be applied in the field as for treadmill exercise. The review sets out fundamental physiological pathways, the entailment of which may represent a limiting factor to performance, while taking into account the individual's status, including anamnesis and the possibility of actual disease being present. Tests that assess the possible roles of several body systems, as causes of limited performance, are discussed. These systems include pulmonary, cardiovascular and neuromuscular systems. The evaluation of anaerobic and aerobic energy pathways is also discussed. Emphasis is given to the assessment of pulmonary ventilation by techniques such as spirometry and ergospirometry. These techniques are considered to be of particular potential for further development.

Evidence-based respiratory medicine in horses

It is clear from a review of the current scientific literature that an evidence-based approach to medical treatment of equine respiratory disease can be applied, at least in the instance of common lower respiratory diseases. In particular, there is clear evidence for efficacious treatments for recurrent airway obstruction and exercise-induced pulmonary hemorrhage, and with the recognition of this evidence, these treatments should be the first to be considered by a practitioner when treating these conditions. The purpose of this article is not only to identify the existence of relevant high-quality studies for incorporation into an evidence-based veterinary medicine approach to patient care, but to highlight the features of those studies that should be considered when evaluating their value in individual situations.

Randomized, controlled study of inhaled fluticasone propionate, oral administration of prednisone, and environmental management of horses with recurrent airway obstruction

OBJECTIVE

To determine whether administration of glucocorticoids provides additional benefits to environmental management of horses with recurrent airway obstruction (RAO).

ANIMALS

28 horses with RAO.

PROCEDURE

Horses were classified as having mild, moderate, or severe RAO. Within each category, horses were randomly assigned to receive inhaled fluticasone propionate, inhaled control substance, or oral administration of prednisone. During the 4-week study, horses were maintained outdoors and fed a pelleted feed. Clinical scores, pulmonary function, results of cytologic examination of bronchoalveolar lavage fluid (BALF), and adrenal gland function were determined before and 2 and 4 weeks after initiation of treatment.

RESULTS

Clinical score and pulmonary function of all RAO-affected horses improved during the treatment period. After 4 weeks, clinical scores and pulmonary function of horses treated with a glucocorticoid were not different from those for the control treatment. In horses with severe RAO, treatment with fluticasone for 2 weeks resulted in significantly greater improvement in pulmonary function, compared with pulmonary function after treatment with prednisone or the control substance. Treatment with a glucocorticoid for 4 weeks and a low-dust environment did not have any effect on cellular content of BALF Treatment with prednisone for 2 weeks resulted in a significant decrease in serum cortisol concentration, compared with concentrations after administration of fluticasone or the control substance.

CONCLUSIONS AND CLINICAL RELEVANCE

Environmental management is the most important factor in the treatment of horses with RAO. Early treatment with inhaled fluticasone can help accelerate recovery of horses with severe RAO.

Biological availability of inhaled fluticasone propionate in horses

Healthy horses received aerosolised, intranasal or oral doses of 3 mg of fluticasone propionate evenly divided over morning and evening treatments for seven days. The bioavailability of the drug was determined in terms of the suppression of the endogenous cortisol concentrations in the horses during the period of treatment. The horses which received the aerosolised drug had significantly lower concentrations of endogenous cortisol on days 5 and 8 than the horses which received aerosolised placebo. The horses which received nasal and oral doses of fluticasone propionate showed no significant changes in their endogenous cortisol concentrations.

Efficacy of oral and intravenous dexamethasone in horses with recurrent airway obstruction

REASONS FOR PERFORMING STUDY

Although the efficacy of dexamethasone for the treatment of recurrent airway obstruction (RAO) has been documented, the speed of onset of effect and duration of action are unknown, as is the efficacy of orally administered dexamethasone with or without fasting.

OBJECTIVES

To document the time of onset of effect and duration of action of a dexamethasone solution i.v. or orally with and without fasting.

METHODS

Protocol 1 used 8 RAO-affected horses with airway obstruction in a crossover design experiment that compared the effect of i.v. saline and dexamethasone (0.1 mg/kg bwt) on pulmonary function over 4 h. Protocol 2 used 6 similar horses to compare, in a crossover design, the effects of dexamethasone i.v. (0.1 mg/kg bwt), dexamethasone per os (0.164 mg/kg bwt) with and without prior fasting, and dexamethasone per os (0.082 mg/kg) with fasting.

RESULTS

Dexamethasone i.v. caused significant improvement in lung function within 2 h with a peak effect at 4-6 h. Dexamethasone per os was effective within 6 h with peak effect at 24 h at a dose of 0.164 mg/kg bwt prior to feeding. The duration of effect was, for all dexamethasone treatments, statistically significant for 30 h when compared to saline and tended to have a longer duration of effect when used orally. Dexamethasone per os at a dose of 0.164 mg/kg bwt to fed horses had mean effects comparable to dexamethasone at a dose of 0.082 mg/kg bwt per os given to fasted horses, indicating that feeding decreases bioavailability.

CONCLUSIONS

Dexamethasone administered i.v. has a rapid onset of action in RAO-affected horses. Oral administration of a bioequivalent dose of the same solution to fasted horses is as effective as i.v. administration and tends to have longer duration of action. Fasting horses before oral administration of dexamethasone improves the efficacy of treatment.

POTENTIAL RELEVANCE

Oral administration to fasted horses of a dexamethasone solution intended for i.v. use provides an effective treatment for RAO-affected animals.

Sensitive liquid chromatographic/tandem mass spectrometric method for the determination of beclomethasone dipropionate and its metabolites in equine plasma and urine

Beclomethasone dipropionate (BDP) is a potent pro-drug to beclomethasone (BOH) and is used in the treatment of chronic and acute respiratory disorders in the horse. The therapeutic dose of BDP (325 microg per horse) by inhalation results in very low plasma and urinary concentrations of BDP and its metabolites that pose a challenge to detection and confirmation by equine forensic laboratories. To solve this problem, a method involving the use of a liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) was developed for the detection, confirmation and quantification of the analytes in equine samples. Ammonium formate or acetate buffer added to LC mobile phase favored the formation of [M + H](+) ions from BDP and its metabolites, whereas formic acid led to the formation of sodium and potassium adduct ions ([M + Na](+), [M + K](+)) together with [M + H](+) ions. Acetonitrile, on the other hand, favored the formation of abundant solvent adduct ions [M + H + CH(3)CN](+) with the analytes under electrospray ionization (ESI) and atmospheric pressure chemical ionization conditions. In contrast, methanol formed much less solvent adduct ions than acetonitrile. The solvent adduct ions were thermally stable and could not be completely desolvated under the experimental conditions, but they were very fragile to collision-induced dissociation (CID). Interestingly, these solvent adduct ions were observed on a triple-quadrupole mass spectrometry but not on an ion trap instrument where helium used as a damping gas in the ion trap might cause the solvent adduct ions desolvated by collision. By CID studies on the [M + H](+) ions of BDP and its metabolites, their fragmentation paths were proposed. In equine plasma at ambient temperature over 2 h, BDP and B21P were hydrolyzed in part to B17P and BOH, respectively, but B17P was not hydrolyzed. Sodium fluoride added to equine plasma inhibited the hydrolysis of BDP and B21P. The matrix effect in ESI was evaluated in equine plasma and urine samples. The method involved the extraction of BDP and its metabolites from equine plasma and urine samples by methyl tert-butyl ether, resolution on a C(8) column with a mobile phase gradient consisting of methanol and ammonium formate (2 mmol l(-1), pH 3.4) and multiple reaction monitoring for the analytes on a triple-quadrupole mass spectrometer. The detection limit was 13 pg ml(-1) for BDP and B17P, 25 pg ml(-1) for BOH and 50 pg ml(-1) for B21P in plasma and 25 pg ml(-1) for BOH in urine. The method was successfully applied to the analysis of equine plasma and urine samples for the analytes following administration of BDP to horses by inhalation. B17P, the major and active metabolite of BDP, was detected and quantified in equine plasma up to 4 h post-administration by inhalation of a very low therapeutic dose (325 microg per horse) of BDP.

Recurrent airway obstruction--heaves

Heaves, or recurrent airway obstruction (RAO), is a chronic respiratory disease featuring lower airway inflammation, bronchoconstriction, and mucus accumulation. Inhaled organic dusts and T helper 2 type immunologic reactions are involved in the complex pathophysiology of RAO. Clinical signs vary and alternate with remission periods. The diagnosis is often based on history and clinical examination in severe cases, but bronchoalveolar lavage may be useful for the detection of early cases. The most important aspect of treatment is to avoid exposure to allergens. Corticosteroids may be administered systemically or by inhalation in combination with bronchodilators and environmental control.

Equine recurrent airway obstruction: pathogenesis, diagnosis, and patient management

Recurrent airway obstruction is a condition that affects some older horses maintained in confinement. Clinical signs range from exercise intolerance with occasional cough to dyspnea at rest. Bronchoalveolar lavage cytology is characterized by neutrophilic leukocytosis (15%-85%) and is recommended for making the diagnosis in horses with mild to moderate disease. Environmental management combined with periodic bronchodilator and antiinflammatory corticosteroid therapy yields the best prognosis for disease remission.

Effects of inhaled ipratropium bromide on breathing mechanics and gas exchange in exercising horses with chronic obstructive pulmonary disease

Six Warmblood horses suffering an acute exacerbation of COPD were tested to investigate whether inhalation of ipratropium bromide (IB) dry powder (2,400 microg) 30 min preexercise would improve their exercise capacity. A cross-over protocol with an inert powder placebo (P) was used. Mechanics of breathing and arterial blood gases were determined before treatment, after treatment but pre-exercise, and during an incremental exercise test. Oxygen consumption (VO2) was also measured before and during exercise, and the time to fatigue recorded. Inhalation of IB reduced total pulmonary resistance (RL) and maximum intrapleural pressure changes (deltaPpl(max)) and increased dynamic compliance before exercise. The onset of exercise was associated with a marked decrease in RL in P-treated horses but not those receiving IB, so that RL during exercise was not affected by treatment. Although deltaPpl(max) was lower at 8,9 and 10 m/s with IB, there were no treatment-related changes in VO2, blood gases, time to fatigue or any other measurement of breathing mechanics. Therefore, although inhalation of IB prior to exercise may have improved deltaPpl(max), it had no apparent impact on the horses' capacity for exercise.

Efficacy of three corticosteroids for the treatment of heaves

This study used a cross-over design to compare the efficacy of 3 corticosteroids for the relief of airway obstruction and inflammation in 9 heaves-affected horses. The severity of airway obstruction and inflammation was quantified by measurement of lung function and by bronchoalveolar lavage fluid (BALF) cytology, respectively. Airway obstruction was induced by stabling the horses and they remained stabled during the 10 day treatment period. Lung function was measured before treatment (baseline), at Days 3, 7, and 10 of treatment, and after 30 days at pasture. BALF cytology was investigated at baseline, Day 10, and at pasture. All 9 horses received the following 4 treatments in random order: no treatment, daily oral prednisone tablets (1 mg/kg), daily i.v. dexamethasone solution (0.1 mg/kg), and i.m. dexamethasone-21-isonicotinate (0.04 mg/kg) every 3 days. When horses received no treatment, lung function did not change significantly during stabling but improved at pasture. In all horses, daily i.v. administration of dexamethasone solution improved lung function within 3 days to levels as good as or better than those measured at pasture. Dexamethasone-21-isonicotinate was rapidly effective in 8 of 9 horses. The other horse did not respond to this drug. Prednisone tablets were without effect on Days 3 and 7 of treatment, but by Day 10, 5 of 9 horses showed some improvement in lung function. Dexamethasone i.v. solution decreased the percent neutrophils in BALF at Day 10. Other treatments had no effect on BALF cytology. These results demonstrate that dexamethasone rapidly relieved airway obstruction in heaves-affected horses. Oral prednisone had inconsistent effects but may be beneficial in some horses after more than a week of treatment.

Pulmonary function and adrenal gland suppression with incremental doses of aerosolized beclomethasone dipropionate in horses with recurrent airway obstruction

OBJECTIVE

To evaluate clinical response, pulmonary function, and adrenal gland response to incremental doses of beclomethasone dipropionate in horses with recurrent airway obstruction.

DESIGN

Crossover trial.

ANIMALS

8 horses with recurrent airway obstruction.

PROCEDURE

Horses randomly assigned to 4 groups were treated twice daily via aerosol administration of placebo or 500, 1,000, or 1,500 micrograms of beclomethasone dipropionate in a crossover design with a 10-day minimum washout period. Subjective assessment of airway obstruction, serum cortisol concentration, and maximum change in pleural pressure during tidal breathing (delta Pplmax) were determined daily prior to morning drug administration, and delta Pplmax was reevaluated 15 minutes after morning drug administration. Pulmonary resistance and dynamic compliance were determined at baseline and approximately 12 hours after the final treatment.

RESULTS

An immediate treatment effect was not identified. Within 24 hours, delta Pplmax and airway obstruction were lower in horses receiving beclomethasone. Onset and magnitude of response was similar among the 3 beclomethasone dose regimens. Pulmonary resistance was improved only after administration of all 3 doses of beclomethasone, whereas dynamic compliance was improved after administration of 1,000 micrograms and 1,500 micrograms of beclomethasone. Reduction in serum cortisol concentration occurred with all 3 beclomethasone dose regimens; however, the magnitude of adrenal gland suppression was greater in horses receiving 1,000 or 1,500 micrograms of beclomethasone.

CONCLUSIONS AND CLINICAL RELEVANCE

Low-dose (500 micrograms) beclomethasone administration caused similar, improvement in pulmonary function, compared with high-dose beclomethasone (1,000 and 1,500 micrograms), with the exception of dynamic compliance, and caused less suppression of endogenous cortisol production.