Cough Suppression, Decongestants Flashcards
Describe the physiological process of coughing
Cough is a 3-phase expulsive motor act characterized by
an inspiratory effort (inspiratory phase), followed by a forced expiratory effort against a closed glottis
(compressive phase), followed by opening of the glottis and rapid expiratory airflow (expulsive phase).
Neural pathways for cough
Cough receptors at the airway bifurcations in the larynx and at the distal esophagus (innervated by sensory nerve endings), link to cough afferents through the vagus and superior laryngeal nerves to the cough center and
cerebral cortex.
How does cough occur?
Laryngeal and pulmonary receptors, RARs, C-fibers, and SARs, provide input to the brainstem medullary central cough generator through the intermediate relay neurons in the nucleus tractus solitaires (NTS). The cough generator then coordinates output to the muscles that cause cough via the phrenic nerves, etc (via release of Ach).
How are afferents relayed?
via TRPV-1 channels (sensitive to temp, capcasin, irritants)
C-fibers are sensitive to what?
TRPM-8 (melastatin-8) channels sensitive to cold or menthol (and pain)
TRPa-1 is sensitive to what?
wasabi, garlic, onion (noxious stimuli)
What is an acute cough?
lasting less than 3 weeks
What is a subacute cough?
lasting 3-8 weeks (chronic 8+)
A productive cough with clear sputum suggests what? Malodorous?
Clear- bronchitis
Malodorous- anaerobic infection
A productive cough with purulent sputum suggests what? Yellow?
Purulent- bronchial infection
yellow-inflammation
What things can cause a non-productive cough?
- viral infection
- bronchospasm/allergies/asthma
- GERD
- airway obstruction
What are some systemic antitussives?
- Dextromethorphan
- Diphenhydramine
- Codeine
- Benzonatate (Tessalon Perles)
What are some topical antitussives?
Camphor and Menthol
What does Guaifenesin do?
it is DOC for productive cough with thick secretions to dilute them
Dextromethorphan is the active ingredient in what drugs?
- NyQuil
- Muxinex DM
- Robitussin
- Vicks
How does Dextromethorphan work?
suppresses the cough reflex by a direct action on the cough center in the medulla (non-opioid)
not THAT effective
How is Dextromethorphan metabolized?
CYP2D6 (into active dextrorphan)
Large doses of Dextromethorphan can cause what?
dissociative hallucinogenic effect (via antagonizing the NMDA receptor)
What are the AEs of Dextromethorphan?
- dizziness, drowsiness, N/V
- constipation
- tachycardia
ICNREASE SEROTONIN LEVELS
Contraindications of Dextromethorphan
- those taking MAO and serotonin uptake inhibitors
- advanced respiratory insufficiency or hepatic disease
What can Dextromethorphan do to children?
can release histamine and cause allergic reaction
What is serotonin syndrome?
causes seizures, aggitation, tachycardia, etc.
What does Diphenhydramine do?
antihistamine H1-receptor antagonist that suppresses the cough reflex by a direct action on the cough center (anticholingeric)
What is Diphenhydramine indicated for?
2nd line for nonproductive cough caused by irritation
What are the other uses of Diphenhydramine (Benadryl)?
cold, allergic rhinitis, urticaria, motion sickness, insomnia, parkinsonism
AEs of Diphenhydramine?
- Drowsiness
- respiratory depression
- dry mouth
- blurred vision
- urinary retention/constipation
Contraindications of Diphenhydramine?
- BPH
- urinary obstruction
- asthma/COPD
- peptic ulcer (via H2 receptor blocking- they produce gastric secretions)
- MAOIs
T or F. The concurrent use of Diphenhydramine with other serotonin increasing drugs is contraindicated
T.
How does codeine work?
it is an opiod analgesic and antitussive that acts on mu receptors and depresses the cough reflex by direct action
Onset of codeine? DOA?
10-30 minutes and acts 4-6 hrs
AEs of codeine?
constipation, sedation
- histamine release
- orthostatic hypotensions
Contraindications of codeine?
- hypersensitivity
- labor of premature birth
- BPH
- asthma/COPD/respiratory failure