Pathophysiology of Cough and Cold

Pathophysiology of Cough and Cold

• Goblet cells produce mucus in the epithelial lining of the trachea and bronchi.
• Cilia transport mucus out of the lungs.

Symptoms of a Cold

• Initial symptoms (1-3 days): sore throat and clear, thin, watery secretions and low grade fever.
• Progression (2-3 days): nasal symptoms and thicker secretions that may be yellow or green.
• Later stage (4-5 days): cough (30% occurrence) and thicker yellow or green secretions.

Types of Cough

• Acute cough lasts less than 3 weeks.
• Sub-acute is between 3-8 weeks.
• Chronic cough persists for more than 8 weeks.

Productive Cough

• Expels secretions from the lower respiratory tract.
• Deemed effective if secretions are occurring and easy to expel.
• Secretions are not a clear diagnostic indicator.

Non-Productive Cough

• A dry or hacking cough.
• Not serving a normal physiological purpose.
• May indicate a viral or bacterial infection.

Treatments for Cough

• Antitussives suppress cough.
• Protussives enhance cough effectiveness to promote clearance of mucus by changing mucus consistency and increasing the volume of exported mucus.

Nasal Decongestants

• Oxymetazoline (Afrin): Administer 2-3 sprays of the 0.05% solution in each nostril every 12 hours.
• Phenylephrine (Neo-synephrine): Administer 2-3 drops/sprays of the 0.25%, 0.5%, or 1% solution in each nostril no more than every 4 hours.
• Onset for both: within 10 minutes.
• Duration for both: Use for no more than 3-5 days.
• Common ADR for both: Dryness/irritation of nasal mucosa and rebound congestion, sneezing.
• Use with caution in patients with HTN, diabetes, thyroid disease, or BPH

Systemic Decongestants

• Phenylephrine and pseudoephedrine are systemic decongestants.
• Direct-Acting: Phenylephrine; this binds directly to alpha-adrenergic receptors.
• Indirect-Acting: Ephedrine; this displaces NE from nerve terminals.
• Mixed: Pseudoephedrine; has both direct and indirect effects.
• Phenylephrine Instructions: Take 10 mg every 4 hours (max 60mg/day).
• Pseudoephedrine Instructions: Take 60 mg every 4-6 hours (max 240 mg/day) or ER 120 mg twice daily.
• Onset: 30 min-1 hour; Duration: no longer than 7 days
• ADRs: Headache, insomnia, restlessness, increased BP and HR, dry mouth, fatigue, urticaria.
• Use with caution in patients with renal insufficiency, HTN, ischemic heart disease, glaucoma, BPH, seizures, or hyperthyroidism.
• Do not use systemic decongestants even if hypertension is controlled, or diabetes.
• Pseudoephedrine is preferred.
• Only sell 3.6g/day and 7.5g/year

Systemic Analgesics

• Includes acetaminophen, Cox inhibitors (aspirin, ibuprofen, naproxen).
• MOA: inhibits synthesis of prostaglandins and inhibits cyclooxygenase.
• ADRs: Reye's syndrome (for aspirin in children), increased bleed risk, stomach pain.

Oral Antitussives: Antihistamines

• Diphenhydramine (1st gen sedative): Is an antihistamine and antagonist on H1 receptor blocking the release of histamine and used for cough and cold.
• Cetirizine (2nd gen non-sedative).
• ADR: causes sedation (less with 2nd gen), QT interval prolongation, and has anticholinergic effects (can't eat, pee, or poop).

Oral Antitussives: Cough

• Dextromorphan (Delsym, Robitussin): Activates sigma opioid receptors on the cough center and treats non-productive coughs, instructions: 10-20mg.
• ADRs: causes drowsiness, nausea, vomiting.
• Potential drug of misuse and "Robo-tripping".

Oral Antitussives: Suppressants

• Suppress cough reflex in the CNS medulla.
• Could be related to codeine, but are a non-opioid version.

Oral Antitussives: Codeine

• A schedule V narcotic, is a Mu receptor agonist.
• Can't contain more than 200mg per 100 mL
• Increases the cough threshold and reduces coughing, for non-productive cough.
• Dosage: 10-20 mg every 4-6 hours as needed (max 120 mg/day)
• Onset: 30 min-1 hr
• ADRs: causes nausea, vomiting, sedation, dizziness, constipation.
• Has potential for abuse or "lean."
• AVOID IN CHILDREN! as it causes codeine to convert to morphine in the body and can harm a child's breathing.

Protussives: Expectorants

• Guaifenesin (Mucinex): Loosens and thins lower respiratory mucus, promoting excretion of fluid to dilate mucosa, prescribed for chronic cough.
• Take 200-400 mg every 4-6 hours as needed (max 2.4 g/day) or ER 600-1200 mg every 12 hours prn (ax 2.4 g/day).
• Onset: 15-30 min and Duration: no more than 7 days.
• URT infection: will resolve in 2 weeks, Post-viral in 3 weeks, Other in 3-4 weeks
• Generally well tolerated but can cause nausea, vomiting, dizziness, headache, rash, diarrhea, drowsiness, stomach pain.
• Encouraged to take with plenty of non-caffeinated liquids.
• Data supporting efficacy is limited and is not recommended by the ACCP cough guidelines.

Topical Antitussives

• Chlophedianol hydrochloride; centrally acting in the medullary cough center, increases cough threshold and reduces cough for non-productive coughs

• 1st gen alkylamine antihistamine has Anticholinergic effects.

• Menthol. Camphor (Vicks VapoRub); stimulates sensory nerve endings within the nose and mucosa, sensitivity is suppressed

• Should not be used in children < 2 years old, may use the bay rub

• Should not be used on nostrils, mouth or damaged skin

• Phenylephrine is an effective nasal decongestant not a systemic one; this is due to its low bioavailability.