What is the drug of choice for an adult patient with a dry cough, considering their overall health and medical history, including conditions such as asthma or Chronic Obstructive Pulmonary Disease (COPD)?

Drug of Choice for Dry Cough

Dextromethorphan is the drug of choice for dry cough in adults, with maximum efficacy at 60 mg doses, offering superior safety compared to codeine-based alternatives. 1, 2

First-Line Approach: Non-Pharmacological

Before prescribing medications, simple home remedies should be recommended as they are equally effective for benign viral cough:

• Honey and lemon mixture is the simplest, cheapest first-line treatment with evidence of patient-reported benefit 1, 2
• Voluntary cough suppression through central modulation may be sufficient to reduce cough frequency 1

Preferred Pharmacological Agent: Dextromethorphan

When pharmacological treatment is necessary, dextromethorphan is the clear choice:

• Non-sedating opiate that centrally suppresses the cough reflex with proven efficacy in meta-analysis 1, 2
• Dose-response relationship exists: commonly prescribed doses are subtherapeutic; maximum cough suppression occurs at 60 mg and can be prolonged 1, 2
• Superior safety profile compared to codeine and other opioid antitussives 2, 3
• FDA-approved as a cough suppressant 4

Critical Dosing Consideration

• Standard over-the-counter doses are often inadequate 1
• Titrate up to 60 mg for optimal effect 1, 2
• Caution: Verify combination preparations don't contain additional ingredients like paracetamol (acetaminophen) at higher doses 1, 2

Alternative Options

For Nocturnal Cough

• First-generation sedating antihistamines (e.g., diphenhydramine, chlorpheniramine) suppress cough and aid sleep 1, 2
• Particularly useful when cough disrupts sleep 1, 3

For Acute, Short-Lived Relief

• Menthol by inhalation (menthol crystals or proprietary capsules) provides acute but short-lived cough suppression 1, 2

For URI or Chronic Bronchitis

• Ipratropium bromide (inhaled) is the only anticholinergic recommended for cough suppression in these conditions 1, 2

Agents NOT Recommended

Codeine and pholcodine should be avoided:

• No greater efficacy than dextromethorphan 1
• Significantly higher adverse side effect profile 1, 2
• Not recommended by major guidelines 1

Central cough suppressants have limited efficacy for URI-related cough:

• Grade D recommendation (no benefit) for acute viral upper respiratory infections 1

Special Considerations for Underlying Conditions

Asthma or COPD

• Do not suppress cough if it serves a protective clearance function 1
• In COPD, cough clearance is important; suppression may be contraindicated 1
• Treat the underlying disease first (bronchodilators, inhaled corticosteroids) rather than suppressing cough 1
• If cough persists despite optimal disease control, dextromethorphan may be used cautiously 1

Chronic Bronchitis

• Dextromethorphan and codeine are recommended for short-term symptomatic relief (Grade B recommendation) 1
• Ipratropium bromide is effective for cough suppression 1

Critical Pitfalls to Avoid

• Using subtherapeutic doses of dextromethorphan (less than 60 mg may be inadequate) 1, 2
• Prescribing codeine when dextromethorphan offers equal efficacy with better safety 1, 2
• Suppressing productive cough in conditions like pneumonia or bronchiectasis where clearance is essential 1
• Failing to identify underlying causes requiring specific treatment (asthma, GERD, post-nasal drip) 1, 2

Red Flags Requiring Medical Evaluation

Patients should seek immediate medical attention if they experience:

• Hemoptysis (coughing up blood) 1, 5
• Breathlessness or tachypnea 1
• Prolonged fever with malaise 1, 5
• Underlying conditions (COPD, heart disease, diabetes, asthma) 1
• Symptoms persisting beyond 3 weeks 1

Clinical Algorithm

1. Assess for red flags requiring immediate evaluation 1
2. Start with honey and lemon for benign viral cough 1, 2
3. If pharmacological treatment needed: Prescribe dextromethorphan up to 60 mg 1, 2
4. For nighttime cough: Consider first-generation antihistamine 1, 3
5. For URI/bronchitis not responding: Consider ipratropium bromide 1, 3
6. Avoid codeine-containing products entirely 1, 2