Chronic obstructive pulmonary disease in horses: pharmacological support and prevention

The chronic obstructive pulmonary disease in horses holds an important place in the factors affecting both sports results and health in the animals. In severe cases, respiratory tract obstruction is accompanied by the development of alveolar emphysema, which leads to a disturbance in ventilation with an increase in signs of cardiovascular and respiratory failure. The aim of the review was to analyze the efficacy and potential danger of drugs used to treat the chronic obstructive pulmonary disease. Limits in the use of corticosteroids due to their high toxicity and common adverse reactions are reported. In the treatment of horses, three groups of bronchodilators are widely used: anticholinergics, β-adrenergic agonists and methylxanthines. Anticholinergics inhibit the interaction of acetylcholine with the M1- and M3-cholinergic receptors of the bronchi. Inhaled administration of ipratropium bromide causes maximum bronchodilation after 1-2 hours with an effect lasting up to 4 hours. The drug reduces the amount of sputum, but not its viscosity. Tachyphylaxis does not develop. The anticholinergic tiоtropium bromide causes longer bronchodilation (up to 24 hours or more). Agonists of β2-adrenergic receptors along with bronchodilation increase mucociliary transportation, stimulate myocardial function, and reduce vascular resistance as well. The major disadvantage of the drugs is a decrease in the efficiency at prolonged usage due to a decrease in the number and sensitivity of β2-receptors. Tachycardia, tremors, hypokalemia, immediate hypersensitivity reaction are prominent slide effects. The safety of methylxanthines remains controversial. Most often they are used in combination with anticholinergics and β2-agonists. The combination of drugs of various mechanisms and duration of action causes pronounced and prolonged bronchodilation. The complex treatment of the chronic obstructive pulmonary disease in horses includes the use of mucolytic and expectorant drugs, and sometimes antibacterial drugs. The basic principles of disease prevention are keeping animal welfare, proper organization of the training process, as well as the processing of feed from dust and molds.