1. Drugs Affecting the Respiratory System

2. Drugs Affecting the Respiratory System
Antihistamines,
Decongestants,
Antitussives,
and
Expectorants

3. Understanding the Common Cold
Most caused by viral infection (rhinovirus or influenza virus—the “flu”)

4. Understanding the Cold
Virus invades tissues (mucosa) of upper respiratory tract, causing upper respiratory infection (URI).
Excessive mucus production results from the inflammatory response to this invasion.
Fluid drips down the pharynx into the esophagus and lower respiratory tract, causing cold symptoms: sore throat, coughing, upset stomach.

5. Irritation of nasal mucosa often triggers the sneeze reflex.
Mucosal irritation also causes release of several inflammatory and vasoactive substances, dilating small blood vessels in the nasal sinuses and causing nasal congestion.

6. Involves combined use of antihistamines, nasal decongestants, antitussives, and expectorants.
Treatment is SYMPTOMATIC only, not curative.
Symptomatic treatment does not eliminate the causative pathogen.

7. Upper Respiratory Tract

8. Treatment of the Common Cold
Difficult to identify whether cause is viral or bacterial.
Treatment is “empiric therapy,” treating the most likely cause.
Antivirals and antibiotics may be used, but viral or bacterial cause may not be easily identified.

9. Antihistamines
Drugs that directly compete with histamine for specific receptor sites.
Two histamine receptors:
H1 histamine
H2 histamine

10. Antihistamines: Mechanism of Action
The binding of H1 blockers to the histamine receptors prevents the adverse consequences of histamine stimulation:
Vasodilation
Increased gastrointestinal and respiratory secretions
Increased capillary permeability

11. Histamine vs. Antihistamine Effects
Smooth Muscle (on exocrine glands)
Histamine effects:
Stimulate salivary, gastric, lacrimal, and bronchial secretions
Antihistamine effects:
Prevent salivary, gastric, lacrimal, and bronchial secretions

12. Histamine vs. Antihistamine Effects
Immune System
(Release of substances commonly associated with allergic reactions)
Histamine effects:
Mast cells release histamine and other substances, resulting in allergic reactions.
Antihistamine effect:
Binds to histamine receptors, thus preventing histamine from causing a response.

13. Antihistamines: Other Effects
Skin:
Block capillary permeability, wheal-and-flare formation, itching
Anticholinergic:
Drying effect that reduces nasal, salivary, and lacrimal gland secretions (runny nose, tearing, and itching eyes)
Sedative:
Some antihistamines cause drowsiness

14. Antihistamines: Therapeutic Uses
Management of:
Nasal allergies
Seasonal or perennial allergic rhinitis (hay fever)
Allergic reactions
Motion sickness
Sleep disorders

15. Antihistamines: Side effects
Anticholinergic (drying) effects, most common:
Dry mouth
Difficulty urinating
Constipation
Changes in vision
Drowsiness
(Mild drowsiness to deep sleep)

16. Decongestants

17. Nasal Congestion Excessive nasal secretions
Inflamed and swollen nasal mucosa
Primary causes:
Allergies
Upper respiratory infections (common cold)

18. Decongestants Two main types are used: Adrenergics (largest group)
Corticosteroids

19. Decongestants Two dosage forms: Oral
Inhaled/topically applied to the nasal membranes

20. Topical Nasal Decongestants
Adrenergics:
ephedrine (Vicks) naphazoline (Privine)
oxymetazoline (Afrin) phenylephrine (Neo Synephrine)
Intranasal Steroids:
beclomethasone dipropionate (Beconase)

21. Nasal Decongestants: Therapeutic Uses
Relief of nasal congestion associated with:
Acute or chronic rhinitis
Common cold
Sinusitis
Hay fever
Other allergies

22. Antitussives

23. Cough Physiology
Respiratory secretions and foreign objects are naturally removed by the
cough reflex
Induces coughing and expectoration
Initiated by irritation of sensory receptors in the respiratory tract

24. Two Basic Types of Cough
Productive Cough
Congested, removes excessive secretions
Nonproductive Cough
Dry cough

25. Coughing Most of the time, coughing is beneficial
Removes excessive secretions
Removes potentially harmful foreign substances
In some situations, coughing can be harmful, such as after hernia repair surgery

26. Antitussives Drugs used to stop or reduce coughing
Opioid and nonopioid (narcotic and non-narcotic)
Used only for NONPRODUCTIVE coughs!

27. Antitussives: Mechanism of Action
Opioid
Suppress the cough reflex by direct action on the cough center in the medulla.
Examples: codeine ,,,hydrocodone

28. Antitussives: Mechanism of Action
Nonopioid
Suppress the cough reflex by numbing the stretch receptors in the respiratory tract and preventing the cough reflex from being stimulated.
Examples: benzonatate (Tessalon) dextromethorphan (Vicks Formula)

29. Antitussives: Therapeutic Uses
Used to stop the cough reflex when the cough is nonproductive and/or harmful

30. Antitussives: Side Effects
Dextromethorphan
Dizziness, drowsiness, nausea
Opioids
Sedation, nausea, vomiting, lightheadedness, constipation

31. Expectorants

32. Expectorants Drugs that aid in the expectoration (removal) of mucus
Reduce the viscosity of secretions
Disintegrate and thin secretions

33. Expectorants: Mechanisms of Action
Direct stimulation or
Reflex stimulation
Final result: thinner mucus that is easier to remove

34. Expectorants: Mechanism of Action
Direct stimulation:
The secretory glands are stimulated directly to increase their production of respiratory tract fluids.
Examples: iodine-containing products such as iodinated glycerol and potassium iodide (direct and indirect stimulation)

35. Expectorants: Mechanism of Action
Reflex stimulation:
Agent causes irritation of the GI tract.
Loosening and thinning of respiratory tract secretions occur in response to this irritation.
Examples: guaifenesin, syrup of ipecac

36. Expectorants: Common Side Effects
guaifenesin
Nausea, vomiting
Gastric irritation

37. Nursing Implications: Expectorants
Expectorants should be used with caution in the elderly, or those with asthma or respiratory insufficiency.
Patients taking expectorants should receive more fluids, if permitted, to help loosen and liquefy secretions.
Report a fever, cough, or other symptoms lasting longer than a week.

38. Bronchodilators

39. Bronchodilators: Xanthine Derivatives
Plant alkaloids: caffeine, theobromine, and theophylline
Only theophylline is used as a bronchodilator

40. Bronchodilators: Xanthine Derivatives Side Effects
Nausea, vomiting, anorexia
Gastroesophageal reflux during sleep
Sinus tachycardia, palpitations, ventricular dysrhythmias
Transient increased urination