Approach to acute cough

Overview ㅡ Differential is broad; focus on ruling out serious illness (ex: cancer). Avoid antibiotics for viral upper respiratory infection (URI) and bronchitis. Acute cough means a cough lasting less than 3 weeks..

Assessment

DIFFERENTIAL DIAGNOSIS ㅡ Viral respiratory syndromes or environmental irritants cause most acute cough, although the differential is very broad and overlaps with chronic cough etiologies. The focus is on ruling out serious illness, particularly pneumonia (table 1).

Table (1). Differential diagnosis of acute cough
Life threatening	Non life threatening diagnosis
Pneumonia	Infectious Upper respiratory tract infection Lower respiratory tract infection
Severe exacerbation of asthma or COPD	Exacerbation of pre-existing condition Asthma Bronchiectasis COPD
Heart failure	ــــــــ

HISTORY ㅡ Elicit duration, frequency, sputum production, and associated symptoms (fever, cough, wheezing, rhinorrhea, sore throat, shortness of breath [SOB], dyspnea on exertion , paroxysmal nocturnal dyspnea [PND], orthopnea, postnasal drip, reflux, chest pain/pleuritic pain). Assess comorbidities (age > 65, asthma, COPD, CHF, immunosuppression), medications, and tobacco/drug use.

PHYSICAL EXAM ㅡ Vital signs including O2 sat, facial tenderness, sinus drainage, erythematous oropharynx, murmur, S3, JVD, LE edema, wheezing, crackles, rhonchi, fremitus, egophony.

Labs/tests ㅡ Consider chest X ray (CXR) if abnormal vitals (T > 38, HR > 100, RR > 24, O2 sat < 94%) OR focal lung findings (consistent with consolidation or effusion). Patients > 65 years, immunocompromised, or with pulmonary and cardiac comorbidities may present atypically with pneumonia and evaluation should be individualized. Consider other common causes such as second-hand smoke, bronchial hyperreactivity, ACE inhibitors, or recent URI with postnasal drip.

Management

Be judicious with antibiotic use, as most studies show no benefit. (likely viral; antibiotic side effects are common). If normal VS and normal exam, or normal CXR, consider symptomatic treatment for acute bronchitis with cough suppressant, bronchodilator (see Table 2), expectorant, increase fluid intake, humidify air. Recent Cochrane systematic review of 18 RCTs comparing various OTC cough preparations with placebo found no conclusive evidence of benefit of any OTC medicine, but found preparations to be generally safe. Conflicting evidence for the effectiveness of guaifenesin and dextromethorphan, with some trials reporting benefit.

If both abnormal vitals and a focal pulmonary exam are present, consider empiric antibiotics for pneumonia even if CXR is normal. Triage patients for inpatient vs outpatient management with clinical prediction tool (e.g., CURB-65). CURB-65 (1 point each for) include Confusion, BUN > 19 mg/dL, RR > 30, SBP < 90 mmHg OR DBP < 60 mmHg, Age ≥ 65 (consider inpatient for score ≥ 2). Advise rest, regular fluids, and home remedies as adjunctive therapy (lemon, honey, others).

Table (2). Medications for acute cough
Type	Medication	Comment
Over-the-counter	Dextromethorphan	Mechanism: cough suppressant 2 of 3 recent trials show benefit (NNT 3-8 from recent study) Dose Adult: 10 to 20 mg PO every 4 hours as needed; or 30 mg PO every 6 to 8 hours as needed. Maximum 120 mg/day PO Children: 2.5 mg to 5 mg PO every 4 hours as needed; or 7.5 mg PO every 6 to 8 hours as needed. Maximum 30 mg/day PO. Use with caution Serious adverse events, including death, have been associated with the misuse of these medications.
	Guaifenesin	Mechanism: respiratory expectorant 1 of 2 trials (the larger trial) showed benefit but avoid using as monotherapy. Also formulated with dextromethorphan. Dose Adult: 200 to 400 mg PO every 4 hours as needed. Max: 6 doses/day (2400 mg/day) Children: 100 to 200 mg PO every 4 hours as needed. Max: 1200 mg/day PO
	Antihistamine/decongestant	Mechanism: vasoconstriction Conflicting evidence for cough suppression, but increased side effects. ACCP guidelines recommend as initial empiric therapy for common cold/URI.
Prescription	Albuterol (Salbutamol)	Mechanism: beta-agonist bronchodilator Decreases symptom duration in acute bronchitis.
	Ipratropium bromide	Mechanism: muscarinic antagonist bronchodilator May attenuate cough related to URI or post-infectious cough.
	Codeine	Mechanism: opiate cough suppressant Two trials show no difference vs placebo for cough duration. Not more effective than dextromethorphan, but more side effects, usually formulated with guaifenesin.
	Benzonatate	Mechanism: anesthetizes respiratory stretch receptors. No trial data to support its use.
	Antibiotics	Mechanism: varies Avoid if no evidence of pneumonia Macrolides (i.e., azithromycin 500 mg PO × 1, then 250 mg PO daily × 4 days) or Tetracyclines (i.e., doxycycline 100 mg PO BID × 7 days) Fluoroquinolone Levofloxacin 750 mg PO daily × 5 days; or Moxifloxacin 400 mg PO daily × 7 days in chronically ill patients or those with recent therapy (within 3 months)
	Antivirals	Oseltamivir (Tamiflu) Mechanism: inhibits flu neuraminidase Most effective when started within 36 hrs of flu symptom onset, 75 mg PO BID × 5 days While the FDA indication is within 48 hrs, the optimal cut-off in the trial was 36 hrs Zanamivir Mechanism: inhibits flu neuraminidase Most effective when started within 36 hrs of flu symptom onset, 2 puffs BID × 5 days While the FDA indication is within 48 hrs, the optimal cut-off in the trial was 36 hrs

References

• Boujaoude, Z.C. and Pratter, M.R. (2009). Clinical Approach to Acute Cough. Lung, 188(S1), pp.41–46. Available at: https://pubmed.ncbi.nlm.nih.gov/19697082

  York, E.M.A. (2019). Acute Cough—Does Anything Help? [online] www.uspharmacist.com. Available at: https://www.uspharmacist.com/article/acute-coughdoes-anything-help#:~:text=An%20acute%20cough%20is%20one

  UpToDate.com. Treatment of subacute and chronic cough in adults. Available at: https://www.uptodate.com/contents/treatment-of-subacute-and-chronic-cough-in-adults