Management of Dry Cough

Step 1 — Classify by Duration

Step 2 — Red Flags (Investigate Beyond Routine Causes)

• Hemoptysis
• New cough in an active smoker > 45 years
• Change in an existing cough or voice character
• Cough in a 55–80 year old with ≥ 30 pack-year smoking history
• Associated: significant dyspnea at rest/night, hoarseness, fever, weight loss, dysphagia, recurrent pneumonia, or any abnormality on exam/imaging

Step 3 — Treat the Underlying Cause (Primary Strategy)

The medical history alone correctly identifies the cause of chronic cough in approximately 70% of patients. — Murray & Nadel's Textbook of Respiratory Medicine

Step 4 — Symptomatic Antitussive Therapy

A. Non-pharmacologic

• First-line symptomatic approach for chronic dry cough
• Comprises: breathing exercises, cough suppression techniques, vocal hygiene training, psychoeducational counseling
• Shown to improve cough symptom scores, cough counts, and quality of life
• Particularly effective in patients with concurrent muscle tension dysphonia or vocal cord dysfunction

B. Pharmacologic — Antitussives

1. Central (Opioid) Antitussives

• Codeine — methylether of morphine; decreases sensitivity of cough centres in the CNS at sub-analgesic doses; adverse effects: constipation, dysphoria, fatigue, dependence risk; limited use in children
• Dextromethorphan — synthetic morphine derivative; equally effective as codeine; blocks medullary cough centre + NMDA receptors; better adverse-effect profile; caution with MAOIs (risk of serotonin syndrome); avoid in children
• Slow-release morphine — reserved for severe chronic/refractory cough; partially effective for idiopathic chronic cough; also addresses anxiety and pain; used palliatively in terminal cancer

2. Peripheral Antitussives

• Benzonatate — chemically related to tetracaine/benzocaine; anesthetizes stretch receptors in respiratory passages, lungs, and pleura; adverse effects: dizziness, oral/throat numbness (worse if capsule is chewed — swallow whole with water)
• Levodropropizine — peripheral inhibitor of sensory cough receptors; favorable benefit/risk profile vs. dextromethorphan

3. Neuromodulators (For Chronic/Refractory Cough)

• Gabapentin — RCT evidence supports reduction in cough frequency, visual analogue scores, and improved Leicester Cough Quality of Life; dose up to 1800 mg/day; acts on voltage-gated ion channels and GABA neurotransmission
• Pregabalin — related to gabapentin; combination with SLT (speech pathology therapy) shown superior to SLT alone for cough severity and frequency (300 mg/day)
• Amitriptyline — low-dose tricyclic; prospective RCT showed complete response in chronic post-infectious cough vs. codeine/guaifenesin (where none had complete response); modulates presynaptic NMDA receptors
• Paroxetine, carbamazepine — used in refractory/neuropathic chronic cough
• Extended-release morphine 5 mg — highest evidence for refractory chronic cough (per KJ Lee's Essential Otolaryngology)

The effectiveness of neuromodulators suggests that chronic cough can be a neuropathic condition in some patients. — Murray & Nadel

C. Expectorants/Mucolytics (For Dry → Productive Conversion)

• Guaifenesin — reduces mucus viscosity, converts dry to productive cough facilitating clearance; widely available OTC
• Acetylcysteine — splits disulfide bonds in mucoproteins; oral form for COPD; note: inhaled form no longer recommended (risk of reflex bronchospasm)
• Aromatic agents (eucalyptus, menthol) — decongestant effects; menthol inhibits capsaicin-induced cough via TRPM8 receptors; useful for short-term relief
• Demulcents — thick preparations coat the mucosa; form the basis of many OTC cough syrups

Step 5 — Novel/Investigational Agents

• P2X3 receptor antagonists (e.g., gefapixant) — reduce cough hypersensitivity via vagal afferent blockade; in clinical development/approval pipeline
• TRP channel antagonists (TRPV1, TRPA1) — investigated but have failed in clinical trials for chronic refractory cough so far

Practical Algorithm Summary

Dry Cough
    ↓
Duration + Red Flags Assessment
    ↓
Acute (<3 wks): Symptomatic; avoid antibiotics unless bacterial cause proven
    ↓
Subacute/Chronic: Identify & treat cause:
    • ACE inhibitor → Stop/Switch
    • GERD → PPI
    • Asthma → ICS + LABA
    • Postnasal drip → Nasal steroids + 1st-gen antihistamine
    ↓
Persistent/Refractory dry cough despite cause-treatment:
    1. Speech & language therapy (first-line non-pharm)
    2. Dextromethorphan or benzonatate (mild-moderate)
    3. Gabapentin/pregabalin (neuromodulator, chronic neuropathic cough)
    4. Amitriptyline (post-infectious chronic cough)
    5. Slow-release morphine (severe/refractory/palliative)

Sources

• Murray & Nadel's Textbook of Respiratory Medicine — Chapters 37 & block 9
• Textbook of Family Medicine (9e) — Chapter: Cough
• Lippincott Illustrated Reviews: Pharmacology — Drugs used to treat cough
• Goldman-Cecil Medicine (International Ed.) — Chapter: Cough
• Recent systematic reviews: PMID 39192278 (cough burden in ILD, 2024) | PMID 40402261 (superior laryngeal nerve block for neuropathic cough, 2025)