Update of therapies for feline asthma (Proceedings)

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Update of therapies for feline asthma (Proceedings)

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Aug 01, 2010

Feline asthma consists of an inflammatory disorder of the lower respiratory system of cats that results in bronchoconstriction and limited airflow to the lungs. Successful therapy of this condition starts with appropriate management of the animal environment and the selection of therapeutic combinations that safely address the long-term and short term needs of the animal. Over the last few years, newer products and routes of administration have allowed to increase safety and efficacy of drug management practices. This report will review some of the newer agents and management practices.

Objectives Of The Presentation

          • To review the basic pathophysiology of feline asthma.
          • To discuss environmental management issues.
          • To discuss the pharmacologic basis of medical treatment.
          • To evaluate current treatment approaches.

Key Pathophysiologic Points

The major signs of feline asthma include recurrent episodes of cough and dyspnea resulting from bronchoconstriction.

Although the pathophysiology of feline asthma is not completely understood, it is presumed to originate as a type I hypersensitivity reaction. Inhaled allergens react with immunoglobulin E (IgE) that is bound to previously sensitized mast cells. This stimulates the degranulation of mast cells and the sudden release of inflammatory mediators (histamine, serotonin, cytokines, etc) locally. These mediate the vasodilatation, vascular leakage and smooth muscle spasm that characterizes the initial response phase, as well as the vascular permeability, neutrophil and eosinophil attraction and the bronchial spasm that characterize the asthma attack.

Relevant Therapeutic Points

          • Asthma in cats is believed to have an important allergic/inflammatory component1,2. Likely allergens include dust, cigarette smoke, mildew and mold, parasitic proteins, pollen, cat litter, and possibly household chemicals. Although there is no conclusive proof of an allergic etiology in cats, some studies suggest that allergen avoidance contribute significantly to control this condition3,4. While exact determination of the causing allergen/s may be a difficult task, many can be easily eliminated. These include cigarette smoke, mildew and mold and household chemicals. Other potential allergens such as pollen or dust may require the use of air purifiers. Clay cat litter often needs to be replaced with pine or silicone, preferably unscented.
          • Although it has been suggested that dietary hypersensitivity may be related to feline asthma, there is no scientific evidence supporting such point.
          • Although the acute clinical signs (cough and dyspnea) are related to bronchial constriction, treatment with bronchodilators alone, without addressing the underlying inflammatory process, is not likely succeed in the long run.
          • Treatment directed to decrease the inflammatory component of the disease while addressing occasional flare-ups constitute the most appropriate strategy.
          • Decision to treat can be based on both frequency and severity of symptoms. Orientative guidelines have been proposed5:
          • Moderate symptoms occur less than once weekly in untreated patients:
          • Treat patients with bronchodilators to correct the acute episodes.
          • Moderate symptoms occur more than once weekly in untreated patients:
          • Treat with an oral corticosteroid, e.g. prednisolone 1-2 mg/kg q12h PO for 5-7 days.
          • If signs frequency decreases, slowly taper the dose over the next 2-3 months.
          • Treat with bronchodilators as needed for acute exacerbations.

     Alternatively:
          • Treat with an oral corticosteroid, e.g. prednisolone 1 mg/kg q12h PO for 5 days and then q24h for 5 more days.
          • Treat with one 100 μg fluticasone puff q12h
          • If after 10 days of combined oral/inhaled therapy signs improve, the cat can be weaned off the oral prednisolone.
          • Treat with bronchodilators as needed for acute exacerbations.