What treatment options are available for a persistent cough in an adult with no known medical history that is not getting better?

Treatment of Persistent Cough in Adults

For a persistent cough not improving, you must first determine the duration and systematically identify the underlying cause using an anatomic diagnostic protocol, as the treatment depends entirely on whether this is postinfectious cough (3-8 weeks), chronic cough (>8 weeks), or an acute process that should have resolved. 1

Initial Assessment and Duration-Based Classification

The duration of cough fundamentally changes your diagnostic and therapeutic approach:

• Acute cough (<3 weeks): If still present after typical viral illness duration, consider acute bronchitis and treat symptomatically with dextromethorphan 60 mg (not subtherapeutic doses), first-generation antihistamine/decongestant combinations, or naproxen. 2, 3, 4

• Subacute/postinfectious cough (3-8 weeks): This represents post-viral airway inflammation with bronchial hyperresponsiveness, mucus hypersecretion, and impaired mucociliary clearance. 1

• Chronic cough (>8 weeks): Requires systematic evaluation for the three most common causes: upper airway cough syndrome (UACS, formerly postnasal drip), asthma, and gastroesophageal reflux disease (GERD). 1

Treatment Algorithm for Postinfectious Cough (3-8 Weeks Duration)

If the cough has persisted 3-8 weeks following an acute respiratory infection:

First-line therapy: Trial of inhaled ipratropium bromide, which may attenuate the cough through its anticholinergic effects on mucus hypersecretion. 1, 3

Second-line therapy: If cough adversely affects quality of life and persists despite ipratropium, add inhaled corticosteroids to address the underlying airway inflammation. 1

Third-line therapy: For severe paroxysms that are disabling, consider prednisone 30-40 mg daily for a short, finite period only after ruling out UACS, asthma, and GERD as alternative causes. 1

Last resort: Central acting antitussives such as codeine or dextromethorphan should only be considered when other measures fail. 1

Critical exclusion: Antibiotics have absolutely no role in postinfectious cough unless bacterial sinusitis or early Bordetella pertussis infection is documented. 1, 3

Treatment Algorithm for Chronic Cough (>8 Weeks Duration)

If cough has persisted beyond 8 weeks, you must abandon the postinfectious cough diagnosis and systematically evaluate for the common causes, which account for 91-98% of cases: 5, 6

Step 1: Evaluate and Treat Upper Airway Cough Syndrome (UACS)

• UACS is the most common cause of chronic cough in adults (29-56% of cases). 7, 5, 6
• Treat empirically with first-generation antihistamine/decongestant combinations (e.g., brompheniramine/pseudoephedrine), NOT second-generation antihistamines. 7, 3
• If upper airway symptoms are present, add topical nasal corticosteroids. 2
• Allow 2-3 weeks for response before moving to next step. 7

Step 2: Evaluate and Treat Asthma/Eosinophilic Bronchitis

• Asthma accounts for 14-25% of chronic cough cases and is frequently misdiagnosed. 3, 5, 6
• Perform objective testing: spirometry, methacholine challenge for bronchial hyperresponsiveness, sputum eosinophils, and exhaled nitric oxide. 7, 2
• If testing is positive or if you're doing an empiric therapeutic trial, prescribe inhaled corticosteroids. 7, 2
• Do NOT prescribe inhaled corticosteroids if objective testing is negative. 2

Step 3: Evaluate and Treat GERD

• GERD accounts for 5-10% of chronic cough and may occur without gastrointestinal symptoms. 2, 5, 6
• Consider intensive acid suppression with proton pump inhibitors for at least 3 months if GERD is suspected. 2
• Do NOT prescribe proton pump inhibitors if the workup for GERD is negative. 2

Step 4: If Cough Remains Unexplained After Proper Evaluation

Only after completing the above systematic evaluation and therapeutic trials should you diagnose unexplained chronic cough: 7

First-line for unexplained cough: Multimodality speech pathology therapy, which includes cough suppression techniques, vocal hygiene, and psychoeducational counseling. This has been shown to decrease objective cough frequency and improve quality of life. 1, 7, 2

Second-line for unexplained cough: Gabapentin, starting at 300 mg once daily and escalating by adding additional doses each day as tolerated up to a maximum of 1,800 mg daily in two divided doses. Discuss potential side effects and risk-benefit profile before initiating, and reassess at 6 months before continuing. 1, 7, 2

Palliative option for refractory cases: Low-dose opiates (e.g., slow-release morphine 5 mg twice daily) may be considered when cough has substantial impact on quality of life and all alternative treatments have failed, particularly in the palliative care setting. 1

Critical Pitfalls to Avoid

• Do not suppress cough without identifying the underlying cause first. The vast majority of chronic cough has an identifiable and treatable cause. 7, 5, 6

• Do not prescribe antibiotics for postinfectious or chronic cough unless bacterial sinusitis or pertussis is documented. 1, 3

• Do not use subtherapeutic doses of dextromethorphan (<60 mg) if using it for symptomatic relief. 2

• Do not miss ACE inhibitor-induced cough if the patient is on these medications—discontinuation is the only uniformly effective treatment. 1

• Do not overlook pertussis if cough has lasted ≥2 weeks with paroxysms, post-tussive vomiting, or inspiratory whooping sound. 1

• Do not diagnose habit or psychogenic cough until after extensive evaluation has ruled out all organic causes and specific psychiatric therapy has been attempted. 1

Red Flags Requiring Immediate Evaluation

Refer urgently or obtain chest imaging if any of the following are present:

• Hemoptysis 2
• Fever >4 days, tachycardia, tachypnea, or abnormal vital signs suggesting pneumonia 3
• New focal chest signs on examination 3
• Progressive dyspnea or breathlessness 2
• Smoking history with chronic cough (consider malignancy) 2