Respiratory System Pharmacology

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

The respiratory system is a highly dynamic and complex collection of organs. This lesson serves to introduce some basic concepts related to disorders affecting this system and potential therapeutic measures thereof.

The Respiratory System

Inhaling, exhaling, coughing, and sneezing. They all have to do with our respiratory system, a group of organs, tissues, and structures whose main function is to transfer oxygen from the environment and into the blood and transfer carbon dioxide from the body and into the environment. This system includes things you are well aware of, like the nose, trachea (windpipe), as well as the lungs. All of these, and other structures of the respiratory system, can be afflicted with a wide variety of maladies.

What you'll learn in this lesson is a bit about some of these disorders as well as some of the drugs that may treat them and the basics of how they work.

Asthma & Cough

One of the most famous respiratory system disorders is asthma, a chronic (long-term) inflammatory disorder that affects the airways. In asthma, a person's airways (bronchi) constrict. This results in everything from difficulty breathing to coughing to chest tightness. In people with asthma, the goal of pharmacological therapy is to minimize not only the frequency of asthma symptoms but also their intensity.

One of the ways this can be accomplished is through the use of medications called beta-2 adrenergic agonists. Specifically, inhaled beta-2 agonists. Beta-2 adrenergic agonists work by directly causing the smooth muscles of the airways to chill out, or relax. In other words, it is the smooth muscles of the airways that constrict the bronchi, like a clenched fist around a straw. Beta-2 adrenergic agonists tell the fist to unclench, so to speak, and the straw opens up to allow for air to pass. Names of well-known beta-2 agonists include albuterol and levalbuterol.

As you just learned, one of the potential signs of asthma is a cough. A cough, of course, can have plenty of other causes, like a viral infection as per the flu. The cough itself is an important respiratory system defense mechanism, as it helps to expel irritants. In some cases, a doctor will not want to suppress a cough. In fact, it's always better to treat the underlying cause of the cough than to suppress the cough itself. However, in some instances and conditions, the cough becomes so excessive and even irritating and painful that it may be advisable to use a medication to stop it.

One medication that can help suppress this is codeine, an opiate. Opiates are drugs derived from the opium poppy plant and are generally used to minimize moderate to severe pain. However, opiates also help suppress coughing by dulling the sensitivity of cough centers in the brain to stimulation coming from the respiratory system. But powerful opiates that can do this, such as codeine, also carry the potential for some bad side-effects as well as addiction. That's why safer drugs, such as dextromethorphan, a synthetic derivative of another powerful opiate called morphine, may be used instead.

Allergic Rhinitis & Pneumonia

Cough is also a part of rhinitis, the inflammation of the mucous membranes lining the nose. 'Rhino-' in rhinitis means nose. Remember that by thinking of rhinoceros and the horn on its nose. Rhinitis causes coughing, sneezing, itchy nose and eyes, and nasal congestion among other things. Rhinits can be caused by something like an allergen. Allergens can be dust, animal dander, as well as pollen.

Most of these signs are caused by, in big part, a molecule called histamine that is released from immune system cells called mast cells. So, we use antihistamines, such as the H1 receptor blockers, in order to try and prevent these signs and symptoms. Note that antihistamines are better at preventing allergic rhinitis. They're not as good at treating it once the snot hits the fan. Instead, drugs called corticosteroids are better at treating the allergic rhinitis. Corticosteroids help suppress many cells and molecules related to allergic rhinitis. Names of these corticosteroid drugs include beclomethasone and fluticasone.

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