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write mode of action of antitussive drug​

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VETERINARY / ... / ANTITUSSIVE DRUGS

Antitussive Drugs

By Patricia M. Dowling, DVM, MSc, DACVIM, DACVCP, Veterinary Clinical Pharmacology, Western College of Veterinary Medicine, University of Saskatchewan

Last full review/revision Oct 2014 | Content last modified Oct 2014

The cough reflex

The cough reflex

COURTESY OF DR. PATRICIA DOWLING.

A cough is a sudden, explosive exhalation of air that functions to clear material from the airways. Coughing is one way in which the lungs and airways are protected from inhaled particles. Coughing sometimes brings up sputum (also called phlegm), a mixture of mucus, debris, and cells expelled from the lungs. The cough reflex has both sensory (afferent) and motor (efferent) pathways. The internal laryngeal nerve carries the sensory information away from the area above the glottis in the trachea to the cough center located in the medulla oblongata via the vagus nerve. Stimulation of this area by dust or foreign particles produces a cough to remove the foreign material from the respiratory tract before it reaches the lungs. Mucus production in the bronchi is an airway defense mechanism, and it increases with inflammation and infection. In dogs and cats, coughing occurs because of a primary disease process, such as Bordetella bronchiseptica infection ("kennel cough") or chronic bronchitis in dogs, or feline asthma or heartworm-associated respiratory disease in cats. In most cases, addressing the primary disease will resolve the cough. Antitussive therapy is symptomatic and is primarily for the comfort of the animal and the owner. Most antitussive drugs are opiates or opioids that directly suppress the cough center in the medulla oblongata (see Table: Antitussive Drugs). The antitussive effect does not appear to be related to the binding of traditional opiate receptors (mu and kappa). For example, dextromethorphan is an opioid derivative with good antitussive activity, but it does not have activity at opiate receptors and is not analgesic or addictive.