Respiratory Tract drugs: Antihistamines and Antitussives - Ch. 80 Flashcards
What is a kind of cell that releases histamine (and other substances)?
Mast cells
What does histamine cause?
Symptoms of allergic reactions
What are antihistamines?
Histamine receptor antagonists
-Drugs that compete with histamine receptor site
What are the 2 histamine receptor subtypes?
H1 (histamine1)
H2 (histamine2)
What kind of histamine receptor do antihistamines bind to?
H1
-They are H1 antagonists
-Some also act as anticholinergic drugs
What percent of the general population is sensitive to various environmental allergies?
10%-20%
What are some histamine-mediated disorders?
Allergic rhinitis hay fever, mould and dust allergies)
Anaphylaxis
Angioedema
Drug fevers -usually young kids
Insect bite reactions
Urticaria (redness and itching)
What is the mechanism of action of antihistamines?
Block of H1 receptors prevents the adverse consequences of histamine receptor stimulation
What are the physiological effects of antihistamines?
Vasodilation
Increased GI and respiratory secretion
Increased capillary permeability
What is the histamine action on small blood vessels?
Dilation and increased permeability
Swelling (fluid from plasma into interstitial fluid)
What is the antihistamine effect on small blood vessels?
Reduce dilation of blood vessels
Reduce increased permeability of blood vessels
What is the histamine action on exocrine glands?
Stimulate salivary, lacrimal and bronchial secretions
What is the antihistamine effect on exocrine glands?
Reduce salivary, lacrimal and bronchial secretions
What is another use for antihistamines?
Skin
-Reduce capillary permeability
-Wheal-and-flare formation
-Itching (pruritus)
What are some palliative, not curative, treatments using antihistamines?
Nasal allergies
Seasonal or perennial allergic rhinitis (hay fever)
Allergic reactions
Motion sickness
Sleep disorders
What are the 2 main types of Antihistamines?
Traditional (1950s)
Nonsedating/peripherally acting (1980s)
What are traditional antihistamines?
older drugs
Antagonists of H1 receptors
Anticholinergic effects
Nighttime relief
What do traditional antihistamines do when they act on peripheral H1 receptors?
Reduce respiratory/eye symptoms
What do traditional antihistamines do when they act on central H1 receptors?
Cause sedation
What are some examples of traditional antihistamines?
Diphenhydramine (Benadryl)
Chlorpheniramine
Why are traditional antihistamines used as a sleep aid?
Because they cause sedation/drowsiness
What is the anticholinergic effect of traditional antihistamines?
ACh on cell cholinergic receptors
-Parasympathetic NS action (peripheral)
-CNS (central)
What does the anticholinergic effect of traditional antihistamines cause?
Drying effect that reduces nasal, lacrimal, salivary gland secretions
-runny nose, tearing, itching eyes
-Dry mouth (reduced saliva)
-Difficulty urinating
-Constipation
-Change sin vision (dilated pupils, blurred vision)
What are nonsedating/peripherally acting antihistamines?
Developed to eliminate unwanted adverse effects, mainly sedation
Work peripherally
What is the result of nonsedating/peripherally acting antihistamines working peripherally?
Fewer CNS adverse effects
What is increased/longer in nonsedating antihistamines?
Longer duration of action
increases adherance
Examples of nonsedating/peripherally acting antihistamines?
Loratadine (Claritin)
Desloratadine (Aerius)
Fexofenadine (Allegra)
Cetirizine (Reactin)
What should the nurse do if the client is taking traditional antihistamines?
Instruct clients to report excessive sedation, confusion or hypotension
Client should avoid driving or operating heavy machinery
Do not consume alcohol or other CNS depressants
What is coughing?
Respiratory secretions and foreign objects are naturally removed via cough reflex
What is the cough reflex?
Induces coughing and expectoration
Initiated by irritation of sensory receptors in the respiratory tract
What are the two basic types of coughs?
- Productive
- Nonproductive
What is a productive cough?
Congested, wet, removes excessive secretions
What is a nonproductive cough?
Dry cough
Is coughing always beneficial?
No sometimes can be harmful
e.g, after hernia repair surgery
What drugs are used to stop or reduce coughing?
Antitussives
-Opioids
-Othe ragents
What is the only kind of cough that antitussives are used to treat?
ONLY Nonproductive coughs
How are opioids antitussive?
Suppress the cough reflex
Acts in cough centre of medulla
Examples of antitussive opioids?
Codeine
Hydrocodone
What is a common over the counter (OTC) antitussive?
Dextromethorphan (Benylin)
What is Dextromethorphan (Benylin)?
Synthetic opioid-like compound
-Doesn’t produce morphine-like effects tho
What Traditional antihistamine is a non-opioid antitussive drug?
Diphenhydramine
What are antitussives used for?
Used to stop cough reflex when the cough is nonproductive and/or harmful
What adverse effects are associated with codiene as an antitussive?
Sedation, nausea, vomiting, lightheadedness, constipation
-typical opioid effects
What adverse effects are associated with dextromethorphan (antitussive)?
Dizziness, drowsiness, nausea
-Less CNS effects than codeine
What symptoms should be reported when using antitussives?
Cough lasts more than a week
persisten headache
fever
rash
