The primary aim of therapy in companion animals is to control airway inflammation. Traditional therapy has been based around the anti inflammatory effects of oral glucocorticoids such as prednisolone in combination with bronchodilators such as terbutaline (cats) or theophylline (dogs).
Glucocorticoids also promote bronchodilation by sensitizing α-2 receptors, increasing their numbers and increasing their affinity. Glucocorticoids reduce the formation of leukotrienes and prostaglandins and part of their anti-inflammatory activity is mediated in this way while this also may contribute to bronchodilation. Soluble glucocorticoids can be given intravenously for immediate effect and are valuable by this route in the treatment of acute bronchoconstriction.
Other medication have been used including leukotriene receptor antagonists such as zafirlukast, serotonin antagonists such as cyproheptadine, new generation anti-histamines such as cetirizine, anti-cholinergics such as ipratropium and T-lymphocyte modulators such as cyclosporine A. However, although some of these agents have been widely used in feline medicine, reported efficacy has been very variable and clinical use is based only on anecdotal evidence.
Although infectious agents are rarely isolated in chronic bronchitis, many veterinarians opt to give a short course of broad spectrum antibiotics such as cephalexin or doxycycline. Anthelmintics such as fenbendazole may be useful if a parasitic pneumonitis is suspected.
Environmental assessment is important and a reduction in the amount of inhaled airway irritants may be beneficial. Whilst there are unlikely to be many owners who will give up smoking to aid their pets airway irritability, it is worth pointing out to owners potential contributory causes. Recent anecdotal evidence in the USA has suggested that cats in particular may be allergic to human dander and improvements have been seen in felines which have been excluded from sleeping on the owner’s bed!
In the last few years, inhaled therapy has become increasingly popular and is now widely regarded as the treatment of choice in companion animal lower airway disease. Whilst objective data on their efficacy is currently being collated, widespread anecdotal reports support their firstline use.
In humans it has been shown that the formulation of drugs such as fluticasone proprionate leads to very little systemic absorbtion allowing much higher concentrations to be used locally, where they are needed, in the respiratory tract. The low systemic absorbtion is in marked contrast to oral glucocorticoids such as prednisolone which can have serious side effects at the doses needed to control airway inflammation. These side effects include, but are not limited to, polydypsia/polyuria, diabetes mellitus, hepatic lipidosis, immunosuppression, skin and coat changes, muscle weakness and weight gain (which in itself exacerbates the dyspnoea).
It is this proven high safety margin, ease of administration and efficacy which has lead to their wide spread adoption in human medicine. Now veterinarians can offer this same standard of care to their feline, canine and equine patients.