Allergy and Respiratory Medications
Objectives
1. Identify major antihistamines used to treat breathing problems caused by allergies.
2. Describe the action of antitussive medications.
3. List medications used to treat and prevent asthma attacks.
4. Describe the major actions and adverse reactions of the two main categories of bronchodilators.
5. Identify at least six medications commonly used as decongestants.
6. Describe the mechanism of action for expectorants.
7. List the major contraindications to the use of nasal steroids.
Key Terms
antihistamines (ăn-tĭ-HĭS-tă-mēnz, p. 138)
antitussives (ăn-tĭ-TŬS-ĭvz, p. 142)
bronchodilators (brŏn-kō-DĪ-lā-tŏrz, p. 145)
bronchospasm (BRŎN-kō-spăzm, p. 144)
contraindications (kōn-tră-ĭn-dĭ-KĀ-shŭns, p. 139)
expectorants (ěk-SPĔK-tŏr-ănts, p. 155)
histamine (HĬS-tă-mēn, p. 138)
leukotriene receptor inhibitors (lū-kō-TRĭ-ēn, p. 150)
ototoxic (ŏ-tō-TŎK-sĭk, p. 139)
perennial allergic rhinitis (PAR) (ă-LĔR-jĭk rī-NĪ-tĭs, p. 138)
perennial nonallergic rhinitis (PNAR) (NŎN-ă-lěr-jĭk, p. 138)
precautions (prē-CĂW-shuns, p. 139)
prophylaxis (prŏ-fĭl-ĂK-sĭs, p. 144)
rebound effect (p. 140)
rebound vasodilation (vā-sō-dĭ-LĀ-shŭn, p. 152)
refractoriness (rē-FRĂK-tŏ-rĭ-něs, p. 147)
seasonal allergic rhinitis (SAR) (ă-LŬR-jǐk, p. 138)
sympathomimetics (SĬM-păth-ō-mĭ-MĔT-ĭks, p. 145)
wheezing (p. 144)
xanthines (ZĂN-thēnz, p. 145)
Overview
http://evolve.elsevier.com/Edmunds/LPN/
This chapter looks at medications that affect the respiratory system. The first section, Antihistamines, describes medications used to treat breathing problems caused by allergies. The second section discusses antitussives, or medications used to control coughing. The third section describes the several different categories of medications used for the prophylaxis (prevention) and treatment of asthma and chronic obstructive pulmonary disease (COPD). The fourth and fifth sections cover decongestants and expectorants. The final section discusses nasal steroids used to treat respiratory problems.
Respiratory System
The respiratory system is made up of the lungs and the respiratory passages (Figure 11-1). The upper respiratory system—the oral and nasal cavity, sinuses, pharynx, larynx, and trachea—provides the passages for air to move into the bronchi and lungs (the lower respiratory system). The lungs are divided into lobes. The respiratory system acts to exchange gases (oxygen and carbon dioxide) between the blood and the air and regulates blood pH.
When you take a deep breath (inspiration), the diaphragm drops down; at the same time, the intercostal muscles contract, raising the ribs, increasing the size of the chest, and creating a negative pressure. The negative pressure causes air to rush into the lungs through the respiratory passages. When you breathe out (exhalation), the muscles relax, the pressure increases in the chest, and air is passively forced out of the lungs. Thus, the chest works when breathing in and rests when breathing out.
Any part of the respiratory passages or structures and the lungs themselves may be abnormal. Common problems requiring medication are strictures (narrowed openings) or obstructions (blockage) caused by infection or mucus, collapse of the bronchioles caused by asthma, or infectious masses or tumors. The upper airways are often the site of allergic reactions and bacterial and viral infections.
Antihistamines
Overview
Histamine is a chemical the body produces that causes the inflammatory response. Mast cells found near capillaries and white blood cell basophils contain large amounts of histamine. When the body is injured, histamine is released, and it causes the smooth muscle and vascular system to increase blood flow by opening up the capillaries. This also makes the skin turn red. Fluid then escapes from the capillaries into the tissues, causing swelling. The amount of histamine released after an injury or an allergic reaction varies. Antihistamines relieve the effects of histamine on body organs and structures.
Action
There are two types of antihistamines. Histamine H1— receptor antagonists do not prevent the release of histamine, but rather compete with free histamine for binding at H1-receptor sites on the “effector structures” (e.g., vascular and nonvascular smooth muscles, salivary glands, and respiratory mucosal glands). This blocking action limits the vasodilation (opening) and bronchoconstriction, and increased capillary permeability and reduces the edema (swelling) caused by histamine. Antihistamines also limit the release of acetylcholine, producing an anticholinergic (drying) effect, particularly in the bronchioles and gastrointestinal (GI) system. Antihistamines also have a sedative effect on the central nervous system (CNS). Histamine H2 antagonists compete with histamine at the H2 receptor sites also, but only at the H2 receptors located in the GI tract and so will be discussed later in the text.
Uses
Antihistamine H1 receptor antagonists are used to treat seasonal allergic rhinitis (SAR) and perennial allergic rhinitis (PAR). Allergic rhinitis is a condition in which the patient has a reaction to either outdoor allergens (SAR) or indoor allergens (PAR). Histamine plays a central role in producing most of the typical eye and nasal signs and symptoms such as sneezing, nasal stuffiness, and postnasal drip. These signs and symptoms are also found in patients with perennial nonallergic rhinitis (PNAR), which involves inflammation of the mucous membranes of the nose caused by problems other than allergies. Antihistamines are also used to treat nausea and vomiting, vertigo, insomnia, and to prevent motion sickness, and relieve symptoms of other allergic disorders (particularly urticaria [hives], angioneurotic edema, serum sickness, and prophylactically or to treat reactions to blood or plasma) and as an adjunctive (additional) therapy in anaphylactic (shock) reactions. Antihistamines are used in combination cold-remedy capsules to decrease mucus secretion. First-generation drugs may also be used at bedtime for sedation so people can sleep. Some antihistamines are powerful enough to help treat allergic bronchoconstriction that interferes with breathing.
Antihistamines are classed as either first-generation drugs or second-generation drugs. First-generation drugs are usually those products available over-the-counter (OTC) that patients use before they see a health care provider. Most of these products cross the blood-brain barrier and cause sedation (sleepiness) and are used in particular for helping older adult patients sleep. These products are very effective in helping remove some symptoms of sneezing, itching, and watery rhinorrhea when used for a short time. Because of the high incidence of overdosage of some of these drugs in combination products in children’s cough and cold medications, the FDA has issued a recommendation that OTC cough and cold products not be used in infants and children less than 2 years old. Some products should not be used in children younger than 6 years.
Second-generation antihistamines are newer, more effective, and usually have a more rapid onset of relief of sneezing, pruritus (itching), and watery rhinorrhea. These drugs do not cross the blood-brain barrier and so do not cause significant sedation. These products lack the antimetic effect so their use is limited to allergies. Some are available only by prescription and some OTC. In general, they are less effective against nasal congestion. As newer drugs, they may also be more expensive. Several second generation drugs have been removed from the market because they cause lethal arrhythmias of the heart.
It is important to understand what symptoms the patient is having so that the correct medicine can be taken. This is sometimes a challenge the way OTC products are marketed.
These two generations are further divided into six main groups of antihistamines, depending on their various characteristics and actions. These groups and some specific drugs within each group are listed in Box 11-1.
Adverse Reactions
The most common adverse reactions are due to the anticholinergic activity of the drugs: constipation, blurred vision, dry mouth, urinary retention, and dried thickened secretions due to mucosal drying. Patients may also develop hypertension (high blood pressure), hypotension (low blood pressure), tachycardia (rapid heartbeat), confusion, dizziness, drowsiness, excitation, insomnia (inability to sleep), paradoxic excitation (when a patient shows stimulation rather than the usual sedation), restlessness, sedation, tinnitus (ringing in the ears), anorexia (lack of appetite), diarrhea, nausea, vomiting, difficult or painful urination, impotence, urinary frequency, photosensitivity (abnormal response to exposure to sunlight), rash, urticaria (itching), and nasal congestion.
Antihistamine overdosage is potentially fatal, particularly in children. Any of these products should be used with caution in children and care taken to follow recommended dosages. The symptoms of overdosage occur when the CNS is being stimulated and depressed at the same time.
Drug Dosages
The dosage and delivery system for these medications should be determined based on the weight of the patient, the presence of other medical conditions, and the product. The dose will be carefully determined, based on many factors. Consult a drug handbook for common dosage recommendations.
Drug Interactions
The sedative effect commonly seen with antihistamines is increased when other CNS depressants (such as hypnotics, sedatives, tranquilizers, depressant analgesics, and alcohol) are used along with the antihistamine. The sedative effect of antihistamines also adds to the effect of anticholinergic drugs, and they can strengthen the anticholinergic side effects of monoamine oxidase (MAO) inhibitors, as well as tricyclic antidepressants. When antihistamines are used along with ototoxic drugs (drugs that may damage hearing, such as large doses of aspirin or other salicylates, or streptomycin), the ototoxic effects on the ear may be masked. Antihistamines can decrease the effect of corticosteroids and many hormones. They may also interfere with the effects of anticholinesterase drugs.
Nursing Implications and Patient Teaching
n Assessment
Learn as much as possible about the health history of the patient, including the presence of drug allergy, other drug use, and the presence of asthma, glaucoma, peptic ulcer, prostatic hypertrophy, bladder neck obstruction, respiratory or cardiac disease, and the possibility of pregnancy. Assess the patients work and activities to see if drowsiness might be a problem. A patient with thyroid disease or migraine headaches may be unable to take antihistamines because of the tachycardia (rapid heartbeat) produced. These conditions are either contraindications (factors that rule out the use of a drug) or precautions (factors that indicate a drug should be used with great care) for the use of antihistamines.
As you listen to the patient describe respiratory symptoms, think about whether the problem might be SAR, PAR, or PNAR. The patient may have a history of allergic reactions with allergic nasal congestion (usually seasonal in onset), runny nose, or cough related to a cold or allergy. You may observe symptoms of rhinitis: sneezing, nasal discharge, and inflamed nasal mucosa. The patient may also have edema, dermatographism (wheals, or a raised surface of the skin where it has been scratched), conjunctivitis (inflammation of the inner eyelid and eye), eczema (a chronic condition producing irritation of the skin), insect bites, or contact dermatitis. The nasal mucosa may be swollen, boggy (soft), and pale, and there may be nasal plugging or a clear, watery discharge. Increased sinus pressure may be found when pushing on or palpating the frontal or maxillary sinuses.
These drugs are so common that it is important to learn the drug effects of antihistamine use. In young children, antihistamines may cause hallucinations, convulsions, and even death. Older adult patients are also extremely sensitive to these drugs. Some products may cause teratogenic effects (deformities) in a fetus, although most first and second generation drugs are Category B drugs with a few Category C drugs. Antihistamines should be used with caution in children with a family history of sleep apnea or sudden infant death syndrome (SIDS), or in children with symptoms of Reye syndrome.
n Diagnosis
Through reading the patient’s chart, you will learn why the patient is taking this drug: they may have SAR, PAR, or PNAR, or whether the medication is being given for some other type of allergic reaction. The severity of the symptoms will help in making the nursing diagnosis and deciding what additional nursing actions need to be taken (for example, hydration of the patient [giving additional fluid]).
n Planning
The sedative effect is common to most first generation antihistamines like diphenhydramine (Benadryl), less so with loratadine (Claritin) which is a second-generation antihistamine. The drowsiness caused by antihistamines makes it dangerous for the person taking them to operate heavy machinery or drive.
Some antihistamines may be given parenterally to treat hypersensitivity to blood products, as adjunctive therapy to analgesia, or in treating motion sickness. Most antihistamines are administered orally. Many are available in OTC preparations, although the forms with the highest dosage are available only by prescription. Most drug companies have at least one preparation available by prescription, so that people with Medicare or Medicaid benefits are able to get these drugs with their cards. Antihistamines may be administered rectally, or topically via nasal inhalation or ophthalmic solutions also.
Products that are used when a patient is hospitalized for severe respiratory difficulty are often administered by inhalation therapy by a respiratory therapist—an individual especially trained to use respiratory equipment and to assist the patient to get the most air into and out of their lungs. Watching and working with these respiratory therapists can help nurses increase their own skills to help patients breathe better.
n Implementation
Antihistamines should be taken only when needed. The type and dosage should be chosen for the desired effect and the person being treated. For example, one of the first-generation ethanolamine derivatives makes people very sleepy, and people who do tasks that require alertness probably should not use them. Sometimes a patient is having trouble sleeping and so the doctor may want to give them a drug that will make them drowsy so they might give them a drug from the ethanolamine category. Some drugs cause less drowsiness but may not be as effective in getting rid of the symptoms.
If tolerance (increased resistance to a drug caused by repeated use) to one type of antihistamine develops, the patient might be told to switch to another type to see if it is more helpful. Medications also might be changed or rotated to keep symptoms under control.
Giving oral doses with meals or milk can limit GI side effects however, the nurse should make sure that the medication can be given with foods or milk or if they need to be taken on an empty stomach. Antihistamines given orally are usually well absorbed; parenteral administration is rarely needed. When an intramuscular (IM) preparation such as diphenhydramine is used, it should be injected deep into the muscle to prevent tissue irritation. Intravenous (IV) injection of these agents should be done slowly, with the patient lying down because of the risk of the drug causing a low blood pressure. Long-term use of topical nasal antihistamines increases the risk of sensitization, often causing a rebound effect, or an increase in the symptoms you are trying to stop.
Table 11-1 presents additional information on antihistamines.
Table 11-1
| GENERIC NAME | TRADE NAME | COMMENTS |
| FIRST GENERATION DRUGS | ||
| Alkylamines | Effective at low dosages, practical for daytime use; may cause both CNS stimulation (excitation) and depression (drowsiness); individual response varies | |
| brompheniramine | P-Tex Dimetapp |
|
| chlorpheniramine | Chlor-Trimeton | Low incidence of side effects; available OTC; sustained-release forms not for use in children younger than 6 yr |
| dexchlorpheniramine | Polaramine  |
|
| Ethanolamines | Highest incidence of drowsiness, but GI side effects are infrequent | |
| Clemastine | Tavist | |
| diphenhydramine | Benadryl Genahist Diphenhist Banophen |
Anticholinergic, antitussive, antiemetic, and sedative properties; high incidence of CNS depressant effects; drowsiness increases with use |
| Phenothiazine | Strong CNS depressant effect (drowsiness); may suppress cough reflex or mask signs of intestinal obstruction, brain tumor, or overdosage from toxic drugs (see additional information on phenothiazines in third section of this chapter). Comes as oral, parental, rectal preparations. | |
| promethazine | Phenergan | High incidence of side effects, including severe drowsiness; potent drug with prolonged action; use cautiously in ambulatory patients |
| Piperazine | ||
| hydroxyzine | Vistaril | For pruritus, sedation, adjunct to analgesia, antiemetic |
| Miscellaneous | ||
| azelastine | Astelin nasal spray | For SAR; avoid spraying in eyes |
| SECOND-GENERATION DRUGS | ||
| Piperidines | ||
| azatadine | Optimine | For SAR and PNAR. Comes as a spray |
| cetirizine | Zyrtec | For SAR and PAR; safe for patients with hypersensitivity to hydroxyzine |
| May be taken with or without food | ||
| Patients with renal or hepatic dysfunction require smaller doses | ||
| cyproheptadine | Periactin | For SAR, PAR, and hypersensitivity reactions |
| fexofenadine | Allegra | For SAR; analogue of terfenadine (Seldane) but not associated with cardiac dysrhythmias |
| Allegra D | Patients with renal dysfunction require special dosing | |
| Watch for problems common to decongestants. | ||
| loratadine | Claritin | Place rapidly disintegrating tablets under the tongue |
| Claritin D | Patients with renal or hepatic dysfunction require special dosing every other day. Watch for problems common to decongestants. | |
n Evaluation
The therapeutic effects of antihistamines should decrease the allergy symptoms. Watch for any adverse reactions, which are common but usually mild. Antihistamine use in children and infants is discussed in the Lifespan Considerations box.
Lifespan Considerations
Pediatric
Antihistamines
Modified from McKenry LM, Tessier E, Hogan MA: Mosby’s pharmacology in nursing, ed 22, St Louis, 2005, Mosby.
Older adult patients are more likely to develop side effects such as dizziness, syncope (light-headedness and fainting), confusion, dyskinesia (difficulty in movements of the body), and tremor. These are called extrapyramidal reactions. Considerations for antihistamine use in older adults are discussed in the Lifespan Considerations box.
Lifespan Considerations
Older Adults
Antihistamines
Older adults often have pronounced anticholinergic side or adverse effects, especially constipation, dry mouth, and urinary retention (especially in males).
From McKenry LM, Tessier E, Hogan MA: Mosby’s pharmacology in nursing, ed 22, St Louis, 2005, Mosby.
The respiratory tract may become dry and mucus may thicken when using an antihistamine. Unless there is some reason for a fluid restriction, the patient should be encouraged to drink large amounts of water to thin secretions and keep the mucous membranes moist.
If any skin reactions occur, the patient should stop taking the drug at once and notify the health care provider. The CNS depressant effects of antihistamines may be increased if the patient takes more than the recommended dosage or drinks alcohol while using the product. This could be dangerous.
n Patient and Family Teaching
Antitussives
Overview
Drugs used to relieve coughing are called antitussives. These drugs may either: (1) act centrally on the cough center in the brain, (2) act peripherally by anesthetizing stretch receptors in the respiratory tract, or (3) act locally, primarily by soothing irritated areas in the throat. Products vary in their effectiveness. Antitussives are commonly com-bined with other drugs and are usually sold as OTC drugs. Antitussives containing controlled substances and usually require a prescription, although some states may allow codeine combination products to be sold OTC if the patient signs for them.
Action
The main action of an antitussive depends on whether an opioid antagonist is included. Narcotic or opioid antitussives suppress the cough reflex by acting directly on the cough center in the medulla of the brain. Nonopioid antitussives reduce the cough reflex at its source by anesthetizing stretch receptors in respiratory passages, lungs, and pleura, and by decreasing their activity.
Uses
Antitussives are used for the relief of overactive or nonproductive coughs.
Adverse Reactions
Adverse reactions to antitussives include constipation, drowsiness, dry mouth, nausea, and postural hypotension (low blood pressure resulting in dizziness when a person suddenly stands up).
Drug Interactions
Opioid antitussives have an additive effect with other CNS depressants, so the dosage should be reduced. Most antitussives increase the analgesic effect of aspirin, which may be helpful.
Nursing Implications and Patient Teaching
n Assessment
Learn as much as possible about the health history of the patient, including allergy to antitussives, presence of COPD that may influence the patient’s response to an opioid, possibility of pregnancy, and the use of other drugs or alcohol that may cause drug interactions. These conditions may be contraindications or precautions to the use of antitussives.
Ask about a history of a nonproductive cough or a prolonged and productive cough, which may keep the patient awake at night or cause muscular pain.
n Diagnosis
Take care to learn why the patient has a productive cough. Signs of infection, allergy, or other problems might suggest the source of the cough.
n Planning
Patients with hypersensitivity (allergy) to these drugs or patients with COPD who have problems with breathing are not usually given opioid antitussives. Opioid antitussives may cause drug dependence. Some of the antitussives are Schedule II controlled substances.
These preparations may cause drowsiness, so the patient should be cautioned to avoid tasks requiring alertness after taking the medication.
n Implementation
Antitussives come only in oral forms. They should be used only for short periods. Short therapy decreases the risk of rebound symptoms from prolonged use or the possibility of addiction to opioid products.
Table 11-2 provides additional information on antitussives.
Table 11-2
| GENERIC NAME | TRADE NAME | COMMENTS |
| Opioid Antitussives | ||
codeine  |
NOT FOR USE IN CHILDREN YOUNGER THAN 12 YEARS | |
| codeine phosphate | ||
| codeine sulfate | ||
| hydrocodone | Hycodan | |
| Nonopioid Antitussives | ||
| benzonatate | Tessalon Perles (capsules) | Anesthetizes stretch receptors; drug should not be chewed—local anesthesia of the mouth will develop |
| dextromethorphan | Benylin DM | Centrally depresses cough center |
| Robitussin DM | ||
| Vicks Formula 44 | ||
diphenhydramine  |
Tusstat | Potent antihistamine; safe and effective antitussive |
Indicates “Must-Know Drugs,” or the 35 drugs most prescribers use.
n Evaluation
Watch for therapeutic effects: the cough stops or there is a decrease in frequency and duration of coughing spells, and the patient is able to sleep better at night. Also watch the patient for adverse reactions and drug tolerance.
n Patient and Family Teaching
Asthma Medications 
Overview
Asthma is a condition in which there is increased airway inflammation and mucus production, leading to bronchiolar constriction or narrowing. The patient has no trouble breathing air into the lungs, but the lumens (spaces inside the bronchial tubes) become smaller as the patient attempts to breathe out. This traps air inside the lungs. The patient feels a lack of oxygen and acts by breathing faster, trapping even more air inside the lungs. As some air is forced out through the small, mucus-lined passages during respiratory expiration, a musical respiratory sound called wheezing is heard.
The development of asthma involes the interplay between host factors, particularly genetics, deficiencies of some respiratory enzymes, and environmental exposures (reaction to an allergy, reflex response to cold, dry air, or hard exercise). For some individuals with a genetic tendency, asthma often starts in childhood. For some individuals, it becomes a chronic condition. For others, asthma may be seen only with acute illnesses or exercise.
The National Heart, Lung, and Blood Institute of the National Institutes of Health has published Guidelines for the Diagnosis and Management of Asthma. These guidelines recommend a stepwise plan for using asthma drugs that puts a heavy emphasis on the treatment based on the diagnostic classification. Asthma is grouped into classes of asthma severity. These classes are: (1) intermittent, (2) mild persistent, (3) moderate persistent, and (4) severe persistent. In each category, the severity and frequency of daytime symptoms, nighttime symptoms, and lung function are evaluated. The health care provider should work with the patient on prevention, identification of allergens, patient education regarding self-care, and effects of cultural and ethnic influences on asthma management. Because asthma is primarily a disease of inflammation, corticosteroids (both oral and inhaled) are also used in treatment. Some of the steroids used in treating respiratory problems are discussed briefly here and in greater detail in Chapter 20.
COPD is a slowly worsening, disabling disorder identified by abnormal tests of expiratory flow (air that is breathed out) that do not change very much over several months. The damage to the lungs results from gradual destruction of the alveolar walls (small airway disease), and parenchymal destruction, creating unequal areas of ventilation and perfusion. Thus circulating blood and inhaled air may not come together so that oxygen can be transferred to the blood, and waste products in the blood can be removed. COPD attacks or exacerbations are seen with increases in inflammation from pulmonary infections and in response to pollution and allergic or nonallergic triggers. Unlike patients with asthma, those with COPD are seldom symptom free, and the damage to the lungs is not totally reversible with COPD. Medications that dilate or open the bronchioles and help thin secretions are helpful in reducing symptoms of dyspnea (shortness of breath, difficulty or distress in breathing).
Asthma Prophylaxis (Prevention) Medication
Action
Many drugs treat the symptoms of asthma but few of them prevent the development of it. Cromolyn sodium is an asthma prophylaxis drug that works at the surface of the mst cell as a mast cell stabilizer to prevent the release of histamine, leukotrienes, and slow-reacting substances of anaphylaxis.
Uses
Cromolyn is used to manage bronchial asthma in some patients. How this drug should be used is clearly described in the national guidelines. This drug has no independent, antiinflammatory, or bronchodilator activity, so they are effective primarily for prophylaxis
