Respiratory System

Difficulty in breathing can arise in many ways including partial blockage of an airway by a physical object, damage to the alveoli (emphysema), and the destruction of lung tissue by tuberculosis or other diseases. The most common problems, however, occur because of allergic reactions (usually in the nasal passages), spasmodic contractions of the bronchi (asthma), or an infection. Most infections, usually viral or bacterial in nature, lead to inflammation of various parts of the airways, with consequent fever, irritation, coughing, and phlegm, a gooey combination of mucus and pus. Such inflammations carry the names of their location: rhinitis (nose), pharyngitis (throat), tonsillitis (tonsils), laryngitis (larynx), bronchitis (bronchial tubes) and pneumonia (lungs).

The respiratory system is also damaged by long-term exposure to tobacco smoke and other airborne impurities.

Bronchodilators

When air enters the lungs it passes through narrow tubes called bronchioles. In certain conditions the bronchioles become narrower, either as a result of contraction of the muscles in their walls, inflammation, or as a result of mucous congestion. This tightening of the bronchioles obstructs the flow of air into and out of the lungs and causes breathlessness.

Bronchodilators are prescribed to widen the bronchioles and improve breathing. There are three main groups of bronchodilators: sympathomimetic medicaments, anticholinergics, and xanthine medicaments, which are related to caffeine.

Bronchodilator medicaments act by relaxing the muscles surrounding the bronchioles. Sympathomimetic and anticholinergic medicaments achieve this by interfering with nerve signals passed to the muscles through the autonomic nervous system. Xanthine medicaments are thought to relax the muscles in the bronchioles by a direct effect on the muscle fibers, but their precise action is not known. Corticosteroids decrease inflammation in the lining of the lung.

When taken for the immediate relief of breathlessness, bronchodilators usually improve breathing within a few minutes. Taken to prevent attacks, anti-inflammatories usually start to increase one's capacity for exercise within a few days, and most people find that the frequency of breathless attacks is reduced.

Bronchodilators can produce minor side effects, especially if taken too frequently or in too large a dose. Sympathomimetic medicaments may sometimes cause palpitations and trembling. Typical side effects of anticholinergic medicaments include dry mouth and blurred vision. Xanthine medicaments may cause headaches and palpitations. Inhaled steroids may cause a sore, dry throat or oral thrush.

Since bronchodilators are not often taken by mouth but inhaled, they do not commonly cause serious side effects. However, because of their possible effect on heart rate, sympathomimetic and xanthine medicaments are prescribed with caution for those with heart problems, high blood pressure, or an overactive thyroid gland. Anticholinergic medicaments may not be suitable for people with urinary retention or who have glaucoma.

Decongestants

The usual cause of a blocked nose is swelling of the delicate mucous membrane that lines the nasal passages and excessive production of mucus as a result of inflammation. This may be caused by an infection (usually a common cold) or it may be caused by an allergy -for example, to pollen -a condition known as allergic rhinitis or hay fever. Congestion can also occur in the sinuses (the air spaces in the skull), resulting in sinusitis. Decongestants are medicaments that reduce swelling of the mucous membrane and suppress the production of mucus, therefore helping to clear blocked nasal passages and sinuses.

When the mucous membrane lining the nose is irritated by infection or allergy, the blood vessels supplying the membrane become enlarged. This leads to fluid accumulation in the surrounding tissue and encourages the production of larger-than-normal amounts of mucus.

Most decongestants belong to the sympathomimetic group of medicaments which stimulate the sympathetic part of the autonomic nervous system. One effect of this action is to constrict the blood vessels, so reducing swelling of the lining of the nose and sinuses.

When applied topically in drops or by sprays, these medicaments start to relieve congestion within a few minutes. Decongestants by mouth take a little longer to act, but their effect may last longer.

Topical decongestants used in moderation have few adverse effects because they are not absorbed by the body in large amounts. Decongestants taken by mouth are more likely to cause symptoms related to their action on the sympathetic nervous system, including increased heart rate and trembling. For these reasons they should be used with caution by those with heart problems, high blood pressure, or an overactive thyroid gland.

Used for too long or in excess, decongestants can, after giving initial relief, do more harm than good, causing a "rebound congestion". This can be avoided by taking the minimum effective dose and by using decongestant preparations only when absolutely necessary for a very short period of time.

Medicaments to treat coughs

Coughing is a natural response to irritation of the lungs and air passages, designed to expel harmful substances from the respiratory tract. Common causes of coughing include infection of the respiratory tract (for example, bronchitis or pneumonia), inflammation of the airways caused by asthma, or exposure to certain irritant substances such as smoke or chemical fumes. Depending on their cause, coughs may be productive -that is, phlegm producing -or they may be dry.

In most cases coughing is a helpful reaction that assists the body to get rid of excess phlegm or irritant substances; suppressing the cough may actually delay recovery. However, repeated bouts of coughing can be distressing, sometimes increasing irritation of the air passages. In such cases, medication to ease the cough may be recommended.

There are two main groups of cough remedies, according to whether the cough is productive or dry.

Productive coughs
Mucolytics and expectorants are the groups of medicaments most commonly recommended for productive coughs when simple home remedies such as steam inhalation have failed to "loosen" the cough and make it easier to cough up phlegm. Mucolytics alter the consistency of the phlegm, making it less sticky and easier to cough up. These are often given by inhalation. Expectorants are medicaments that are frequently included in over-the-counter cough and cold remedies. These are said to encourage the production of phlegm, but the overall benefits of such medicaments are doubtful.

Dry coughs
In dry coughs there is no advantage to be gained from promoting the expulsion of phlegm. Medicaments used for dry coughs are given to suppress the coughing mechanism by calming the part of the brain that governs the coughing reflex. Antihistamines are often given for mild coughs, particularly in children. For persistent coughs, mild narcotic medicaments such as codeine are prescribed. All cough suppressants have a generally sedating effect on the brain and nervous system and commonly cause drowsiness and other side effects.

There is a bewildering variety of over-the-counter medications available for treating coughs. Most consist of a syrupy base to which active ingredients and flavorings are added. Many contain a number of different active ingredients, sometimes with contradictory effects: it is not uncommon to find an expectorant (for a productive cough) and a cough suppressant (for a dry cough) included in the same preparation.

It is important to select the correct type of medication for your cough to avoid the risk that you may make your condition worse. For example, using a cough suppressant for a productive cough may prevent you from getting rid of excess phlegm and may thereby delay your recovery. It is best to choose a preparation with a single active ingredient that is appropriate for your type of cough. Diabetics may need to select a sugar-free product. If you are in any doubt ask your physician or pharmacist for advice. Because there is a danger that use of over-the-counter cough remedies to alleviate symptoms may delay the diagnosis of a more serious underlying disorder, it is important to seek medical advice for any cough that persists for longer than two days or if a cough is accompanied by additional symptoms such as fever or blood in the phlegm.

Allergy
Brain and Nervous System
Eyes and Ears
Gastrointestinal Tract
Heart and Circulation
Hormones and Endocrine System
Infections and Infestations
Malignant and Immune Disease
Muscles, and Joints
Reproductive and Urinary Tracts
Skin