Pharmacology of the Respiratory Tract in Animals

Drugs that make respiratory secretions more fluid, helping them to be cleared by natural mechanisms like coughing and sneezing.

Acetylcysteine, a common mucolytic, works by breaking down disulfide bonds in mucus molecules, reducing its thickness.

Drugs that aim to decrease the thickness of bronchial secretions. Their effectiveness is debated.

Potassium iodide, an oral expectorant, can irritate the stomach and indirectly increase bronchial secretions. Its use is controversial.

Drugs that reduce inflammation and congestion in the nasal passages, allowing air to flow more freely.

Antihistamines, while used in humans, have questionable effectiveness in animals for decongestion.

Sympathomimetics, acting as α receptor agonists, can be administered orally or as nasal sprays. However, nasal sprays are poorly tolerated by animals.

Oral administration of sympathomimetics for decongestion avoids their systemic effects on the body.

A group of medications that work by reducing inflammation in the respiratory system. They are particularly useful in treating chronic respiratory conditions like asthma and bronchitis in animals.

A type of anti-inflammatory medication frequently used for respiratory issues in animals. They are effective in reducing airway inflammation, mucus production, and constricted airways.

A group of medications that reduce inflammation by blocking the action of specific inflammatory chemicals called leukotrienes, which are known to cause airway constriction and inflammation.

A class of anti-inflammatory medications that are effective in treating inflammatory respiratory problems in animals. Examples include flunixin meglumine, aspirin, and others.

A type of medication used to alleviate nasal congestion and edema in horses. It works by constricting blood vessels in the nasal mucosa.

A group of medications used to treat bacterial infections in the respiratory tract. They work by killing or inhibiting the growth of bacteria.

A type of medication used to open up the airways by relaxing the muscles that surround them.

A type of medication used to treat a specific form of respiratory distress in horses called 'Recurrent Airway Obstruction (RAO)' or 'Heaves'.

Drugs like morphine, codeine, and hydrocodone that work by reducing the sensitivity of the cough center in the brain, ultimately suppressing the cough reflex.

Drugs that work outside the brain by reducing the irritation or inflammation that triggers the cough reflex.

A type of bronchodilator that works by blocking the action of acetylcholine, a neurotransmitter that causes the airways to constrict.

A type of bronchodilator that works by stimulating the sympathetic nervous system, which causes the airways to relax.

A type of bronchodilator that works by inhibiting the breakdown of cAMP, which helps keep the airways relaxed.

A neurotransmitter that plays a key role in constricting the airways.

A parasympatholytic drug that is administered injectably. It is used to treat bradycardia, reduce salivation during surgery, and reverse the effects of cholinesterase inhibitors.

A parasympatholytic drug that is administered injectably and is used to reduce secretions during anesthesia. It acts by blocking acetylcholine at the muscarinic receptors of the parasympathetic nervous system.

A medication that stimulates the sympathetic nervous system, specifically the 'beta-2' receptors within the respiratory tract. This leads to bronchial relaxation and bronchodilation.

These drugs can cause an increase in heart rate (tachycardia), excitement, and sweating, especially in horses.

They are not completely specific and can activate the 'beta-1' receptors, which are found in the heart.

Beta-2 agonists can decrease the release of inflammatory mediators from mast cells, which are involved in allergic reactions.

A medication that stimulates breathing. It can increase respiratory rate and tidal volume, helping with lung function. It's often used in situations like sedation or respiratory difficulties.

In horses, this medication can cause nervousness, excitability, tremors, rapid heartbeat, and poor coordination. It's prohibited in horse racing due to its potential to affect performance.

It's a phosphodiesterase type V inhibitor. It works by relaxing blood vessels in the lungs, reducing pressure and improving blood flow.

A condition where the pressure in the arteries of the lungs is abnormally high, often caused by factors like heartworm disease, leading to difficulty breathing.

When used in animals, it can improve breathing in newborn animals experiencing respiratory distress. However, it's not a replacement for a breathing tube or mechanical ventilation.

This drug can be used to improve the visual assessment of laryngeal paralysis in lightly anesthetized dogs. The medication enhances laryngeal movement, making it easier to observe abnormalities.

These medications can help reduce nasal congestion by shrinking swollen tissues. However, nasal sprays can be poorly tolerated by animals.

This medication is used to manage pulmonary hypertension. It's commonly employed in patients with heart failure or fluid buildup in the lungs where stimulants are not advisable.

Sympathomimetics, or β-adrenergic agonists, are beneficial for short-term relief of bronchospasm. However, prolonged administration of these drugs can lead to downregulation (reduced receptors) and desensitization of the targeted β receptors, diminishing their effectiveness.

Non-selective sympathomimetics stimulate all α, β1, and β2 receptors. They are used for acute and emergency treatment of bronchoconstriction in animals. Examples include epinephrine, ephedrine, and isoproterenol.

Selective sympathomimetics specifically target β2 receptors, minimizing side effects. They're preferred for long-term use due to their improved safety profile. Examples include terbutaline, albuterol, and clembuterol.

Terbutaline, a selective β2 agonist, is administered orally or parenterally for severe bronchoconstriction in cats. Albuterol, another selective β2 agonist, is used in horses and small animals via aerosolization.

Clembuterol is a partial β2 agonist. It has a less potent effect on bronchodilation but offers additional benefits like inhibiting pro-inflammatory cytokines release. However, it can cause muscle tremors, sweating, and other side effects.

Methylxanthine derivatives, such as theophylline, function by inhibiting phosphodiesterase, an enzyme responsible for breaking down cyclic AMP. This results in bronchodilation by promoting smooth muscle relaxation. They also block adenosine receptors, which can cause bronchoconstriction.

Theophylline, a common methylxanthine derivative, is well absorbed orally and used to induce bronchodilation in horses with RAO (recurrent airway obstruction).

Methylxanthines have an anti-inflammatory effect at low concentrations. They reduce histamine response and suppress the activity of inflammatory cells, especially eosinophils. However, even at low concentrations, they can still act as CNS stimulants.