antihistamines and antitussives Flashcards
antihistamine and antitussive drug uses
- allergic rhinitis (reaction)
- cough
- cough and cold preparations
histamine effects
- released by mast cells
- cause symptoms of allergic reactions
- blood vessel dilation (redness/warmth), leaky capillaries (swelling), nerve ending stimulation (itchy)
antihistamines general info
histamine receptor antagonists
- drugs that compete with histamine for receptor site
- 2 histamine receptor types: H1, H2
H1: cause swelling and allergic rxn symptoms
H2 antagonists: reduce gastric acid in PUD
antihistamine mechanism of action
block H1 receptors and prevent consequences of histamine receptor stimulation
- vasodilation
- increased GI and respiratory secretion
- increased capillary permeability
histamine vs antihistamine effects
cardiovascular/small blood vessels:
- histamine: dilation and increased permeability (swelling)
- antihistamine: reduce dilation of blood vessels, reduce permeability of blood vessels
exocrine glands:
- histamine: stimulate salivary, lacrimal, bronchial secretions
- antihistamine: reduce salivary, lacrimal, bronchial secretions
antihistamine other uses
skin: reduce capillary permeability, wheal and flare formation, and itching (pruritus)
antihistamine indications
palliative treatment (not a cure, make comfortable)
- nasal allergies
- allergic reactions
- seasonal or perennial allergic rhinitis (hay fever)
- motion sickness
- sleep disorders
main types of antihistamines
- traditional
- nonsedating/peripherally acting
traditional antihistamines
- antagonists of H1 receptors
- peripherally: reduce respiratory/eye symptoms
- centrally: cause sedation - CNS
- have anticholinergic effects
- used in nighttime relief (causes drowsiness)
traditional antihistamine example
diphenhydramine
traditional antihistamines other effects
anticholinergic effect
- act on cholinergic receptors
- drying effect that reduces nasal, lacrimal gland and salivary secretions (runny nose, tearing)
traditional antihistamines adverse effects
anticholinergic effects:
- dry mouth (reduce salivary secretions)
- difficulty urinating
- constipation
- changes in vision (dilated pupils, blurred vision - PNS affects lens shape for focus)
- high HR
nonsedating/peripherally acting antihistamines
developed to eliminate unwanted adverse effects (sedation)
- work peripherally (fewer CNS adverse effects)
- longer duration of action (longer half life)
nonsedating/peripherally acting antihistamines examples
- loratadine
- desloratadine
- fexofenadine
- cetirizine
antihistamines nursing implications
traditional:
- report excessive sedation, confusion, hypotension
- avoid driving or operating heavy machinery
- do not consume alcohol or other CNS depressants
antitussives
drugs to reduce cough
- opioids
- other agents
- used only for non productive coughs
cough
respiratory secretions and foreign objects are naturally removed from by the cough reflex
cough reflex:
- induces coughing and expectoration
- initiated by irritation of sensory receptors in the respiratory tract
- reflex happens in the brain when info from the resp tract is sent to CNS then reflex sent back to body to cough
- controlled by medulla oblongata below the level of consciousness
two basic types of cough
1) productive cough (congested, removes excessive secretions)
2) nonproductive cough (dry cough)
- can be harmful in situations like after hernia surgery
do not suppress productive cough (can be beneficial to remove excess secretions and harmful foreign substances)
antitussives mechanism of action
opioids (lower dose than for analgesia):
- suppress cough reflex
- act in cough centre of medulla
ex: codeine, hydrocodone
common OTC antitussive (nonopioid)
dextromethorphan (synthetic opioid like compound)
diphenhydramine (antihistamine)
antitussives indications
used to stop cough reflex when the cough is unproductive and/or harmful
antitussives adverse effects
codeine: sedation, nausea, vomiting, lightheadedness, constipation (typical opioid effects)
dextromethorphan: dizziness, drowsiness, nausea (less CNS effects)
antitussive nursing implications
report:
- cough lasting over a week
- persistent headache
- fever
- rash
only use for nonproductive coughs
