Pharmacology and Nutrition

LEARNING OUTCOMES

1.       Explain common drug use in respiratory system

2.       Explain nursing consideration when administering medication involved respiratory system

 

ANTIHISTAMINES

Histamine is a naturally occurring substance in the body released in response to tissue damage and the presence of microorganisms and allergens invading body tissue. Histamine dilates arterioles to allow increasing blood supply to capillaries and the tissues supplied by capillaries. As a result of this flooding of tissues, they become red and large amounts of fluids leak into interstitial tissues.

The swelling is designed to prevent the microorganisms from traveling to other tissues and organs. This inflammatory response allows for leukocytes (white blood cells) to rush to the area to deactivate and absorb the microorganisms. Many of the discomforts associated with upper respiratory congestion and infections is a result of this swelling from the histamine release, including increased mucus production.

Another manifestation of histamine is itching common at the site of insect bites or other sources of contact inflammation (poison ivy, poison oak, etc.) Antihistamines do not affect the release of histamine, but act primarily to block the action of histamine at the H1 histamine receptor sites. They are, therefore, most useful in the treatment of allergic rhinitis. Their usefulness in the treatment of the common cold is controversial, because of the minimal contribution of histamine to the pathological state of the common cold. The action of antihistamines in the treatment of the common cold, however limited, is believed to be the result of the ability of these agents to exert a feeble anticholinergic action that reduces the amount of mucus secretion.

Antihistamines are capable of causing a wide variety of adverse effects. Many of these agents will produce varying degrees of sedation, particularly when used in combination with other depressant drugs or alcoholic beverages. Because of their chemical similarity to anticholinergic drugs, many antihistamines will cause dry mouth, constipation, blurred vision, and urinary retention. The effects are most prominent and troublesome in the elderly, particularly those with glaucoma or prostatic hypertrophy, as these conditions may be worsened by direct drug action.

The drying effect of antihistamines on the respiratory tract may thicken respiratory tract secretions and increase breathing difficulty in persons with respiratory disorders, such as asthma or emphysema. Antihistamine use is contraindicated in nursing mothers because they may inhibit lactation. Also, they can be secreted in breast milk and endanger a nursing infant. Young children may exhibit signs of hypersensitivity or over dosage to antihistamines 

Note: These agents must be used with caution in clients with bronchial asthma, increased intraocular pressure, prostatic hypertrophy, and in the elderly. Their use with other CNS depressants (e.g., alcoholic beverages) may cause drowsiness and affect alertness. They may be administered with food or milk to reduce GI upset. Their administration should be discontinued at least 4 days prior to allergy skin testing since they may reduce the accuracy of the test.

 

DECONGESTANTS

Nasal decongestants are agents that constrict dilated blood vessels in the nasal mucosa by stimulating alpha1-adrenergic nerve receptors in vascular smooth muscle. This reduces the flow of blood in the edematous area, slows the formation of mucus, permits better drainage, and relieves the client’s discomfort.

Nasal decongestants are administered either topically, by inhalation, or orally. Topically used decongestants are effective and act rapidly. Duration of action varies from several minutes to several hours after a single application. A common problem in the use of these agents is rebounds nasal congestion. This occurs in clients who overuse topical decongestants. Excessive use causes local ischemia and irritation of the nasal mucosa that may lead to extensive secondary vasodilation and congestion.

Rebound congestion can generally be avoided by limiting the use of these agents to several days and by not exceeding recommended doses. Although topical administration of decongestants results in only minimal absorption of drug through the nasal mucosa, adverse systemic effects, such as elevation of blood pressure and CNS stimulation may occur if the decongestant solution drains through the nasal passage and is swallowed by the client.

Note: Oral decongestant drugs are contraindicated in clients with hypertension, heart disease, diabetes mellitus, or hyperthyroidism. Topical nasal decongestants must be used precisely as directed by the physician or the package instructions. Overuse may result in rebound nasal congestion. Clients should be instructed in the appropriate technique for administration of the product to be used. In infants and young children, topical decongestants should be administered about 20 minutes before meals, so that nasal passages will be clear for breathing during sucking or eating. Monitor clients using oral or topical decongestants for development of headaches, insomnia, nervousness, or cardiac palpitations. Avoid the use of these agents in clients receiving monoamine oxidase (MAO) inhibitors

EXPECTORANTS

Expectorants are agents administered orally to stimulate the flow of secretions in the respiratory tract. In doing so, the viscosity of endobronchial secretions and accumulated phlegm is reduced and removal by coughing and ciliary action is facilitated. Greater secretory activity in the respiratory tract also aids in the hydration of dry, irritated tissue and provides a soothing coating to protect against further trauma. There is considerable controversy regarding the therapeutic efficacy of expectorants. This stems from the absence of reliable data to substantiate the reduction of sputum viscosity by expectorants as compared to a placebo.

Expectorants continue to be used, however, on the basis of subjective evidence that they have a useful therapeutic effect. Guaifenesin is the most popular expectorant in current use and is an ingredient in many commercial cough preparations. Guaifenesin is well tolerated by most clients and can be formulated into a palatable syrup. It may cause stomach upset or nausea on rare occasions, because of its stimulatory effect on the production of gastric secretions.

Note: Clients taking expectorants should be taught to cough effectively. This includes sitting in an upright position and taking several slow, deep breaths before coughing. Secretions must be disposed of properly. Sufficient humidification must be added to the air. Encourage fluid intake to help liquefy secretions. May be used with percussion and vibration to help eliminate secretions

 

ANTITUSSIVES

A cough is a physiological mechanism useful in removing foreign material and excessive secretions from the respiratory tract. A cough may be productive or nonproductive, i.e., it may or may not result in the removal of excess respiratory secretions. Involuntary cough should not, therefore, be suppressed unless it causes respiratory discomfort or sleep disturbance, or if the cough does not facilitate removal of excess secretions from the respiratory tract. Both narcotic and nonnarcotic cough suppressants are available. The narcotic agents particularly codeine and hydrocodone, are considered to be the most effective and are reasonably safe to use for most clients. They act in suppressing the cough reflex by a direct depressant effect on the cough center in the medulla of the brain.

Note: Teach client to cough effectively. This includes sitting in an upright position and taking several slow deep breaths before coughing. Secretions must be disposed of properly. Encourage fluid intake. Do not give water after administration of cough syrups. Cough should not be suppressed, when it is productive or beneficial; for example, after surgery (with support). Assess the frequency and nature of cough, as well as the nature of secretions produced. May be used with percussion and vibration to help eliminate secretions.

KEY NURSING IMPLICATIONS

Expectorants and Antitussives

1. Persons with a cough lasting more than 1 week and those with high fever, rash, or persistent headache should be referred to a physician.

2. Assess the nature, duration, frequency, and productivity of cough.

3. Cough syrups given for their local soothing effect should not be followed immediately by food or water.

4. Teach clients about environmental modifications that may decrease cough and/or aid in expectoration of respiratory secretions.

5. Productive coughs should not be suppressed. Clients should be instructed in how to cough productively.

6. Sufficient fluid intake is beneficial in aiding the expectoration of respiratory secretions.

7. Saturated solution of potassium iodide (SSKI) is measured in drops and can be mixed in fruit juices or beverages to disguise its taste. Do not administer this drug to clients allergic to iodine.

8. Teach the client about disposing of secretions properly and preventing respiratory infections.

9. As with all medications, these should be kept out of the reach of children. Syrup of ipecac and the number of the local poison control center should be available if a child accidently ingests an overdose.

 

Bronchodilation can often make the difference between comfort and discomfort or even life and death of a client with an obstructive pulmonary disease. To understand how these drugs work, it is useful to review the processes involved in bronchoconstriction and bronchodilation. When an antigen is introduced into the body of an atopic individual, the antigen combines with a mast cell to form a sensitized mast cell. When this cell is re-exposed to the antigen, it responds with the formation and release of a number of chemical substances, including histamine and leukotrienes. Such chemical substances act either directly to cause bronchoconstriction or indirectly to stimulate the release of acetylcholine, which may cause smooth muscle contraction.

Sympathomimetic Agents Within the mast cell are specialized adrenergic receptors—known as beta2 receptors—which control bronchial smooth muscle tone. When these are stimulated by certain sympathomimetic agents, such as albuterol, bitolterol, epinephrine, ethylnorepinephrine, ephedrine, isoetharine, isoproterenol, metaproterenol, pirbuterol, salmeterol or terbutaline, there is an increase in the formation of cyclic adenosine monophosphate (AMP). This is associated with smooth muscle relaxation and bronchodilation. When these receptors are blocked by a drug such as propranolol (Inderal), bronchoconstriction takes place. This is why beta-adrenergic blocking agents such as propranolol are contraindicated in clients with COPD. Because some of the drugs that stimulate beta2 receptors also stimulate beta1 receptors located in the heart, many of these drugs may be dangerous to use in a client with COPD who also suffers from heart disease. Some of the newer drugs that have been introduced (e.g., albuterol, bitolterol, isoetharine, metaproterenol, pirbuterol, salmeterol, and terbutaline) exert a more selective action on beta2 receptors and do not pose as significant a threat to a client with heart disease.

Note: Client education is very important and must include instruction in ways to decrease environmental irritants, improve humidification of air, and use medication properly, including inhalers. Multiple inhalation medications should not be used, unless ordered by the physician. The client is advised to use the inhaler at the first sign of distress or tightness of the chest and to routinely wash, dry, and replace the mouthpiece. Monitor changes in cardiac function and blood pressure, especially in the elderly.

MUCOLYTICS

Mucolytics reduce the thickness and the stickiness of pulmonary secretions, so that removal by ciliary action and cough is facilitated and pulmonary ventilation can be improved. They are used in the treatment of obstructive pulmonary diseases, such as chronic bronchitis and emphysema, as well as in other diseases, such as cystic fibrosis and pneumonia, in which purulent or non-purulent respiratory blockage may be present. The most commonly used mucolytic agent is acetylcysteine (Mucomyst). The action of this drug is attributed to its ability to break chemical bonds responsible for the high viscosity of mucus.

KEY NURSING IMPLICATIONS

Bronchodilators and Other Respiratory Drugs

1. Assessment focuses on signs and symptoms of respiratory distress, adequacy of gas exchange, and activity tolerance.

2. Clients should be instructed in medication administration procedures (use of an oral inhaler, extender device, and Medi-Mist device) and care of equipment.

3. Mucolytic agents usually have an unpleasant taste, and mouth care should be provided frequently.

4. Bronchodilators may cause tachycardia, cardiac arrhythmias, and gastrointestinal symptoms. Monitor the client carefully.

5. Bronchodilators with central nervous system stimulating effects may cause insomnia. Provide appropriate comfort measures.

6. Bronchodilators such as theophylline, which are irritating to the gastrointestinal tract, should be given with food or milk.

7. Teach clients with COPD to control breathing, to avoid respiratory infections, and to modify their environment to decrease bronchial irritants.

8. Do not wear perfume or colognes when working with clients, especially those with respiratory conditions.

9. Do not use talc or bath powder around these clients.

Self Check 1.5
1.  Explain common drug use in respiratory system
2. Explain the nursing responsibility when administering the drug related.