What syrup is recommended for dry cough and what for wet cough, such as Robitussin DM (dextromethorphan) and Mucinex (guaifenesin)?

Cough Syrup Selection Based on Cough Type

For dry cough, use dextromethorphan-based syrups (like Robitussin DM); for wet/productive cough, use guaifenesin-based syrups (like Mucinex) to help loosen and clear mucus. 1, 2

Dry Cough Management

First-Line Approach

• Start with simple home remedies like honey and lemon, which are often as effective as pharmacological treatments and represent the cheapest, simplest option 2, 3
• If pharmacological treatment is needed, dextromethorphan is the preferred antitussive agent due to its superior safety profile compared to codeine or other opioid alternatives 2, 3

Dextromethorphan Dosing

• Standard over-the-counter dosing (15-30 mg) is often subtherapeutic for optimal cough suppression 2, 3
• Maximum cough reflex suppression occurs at 60 mg, with effective dosing at 10-15 mg three to four times daily (maximum 120 mg/day) 3, 4
• Be cautious with combination products containing acetaminophen or other ingredients when using higher doses 2, 3

Additional Options for Dry Cough

• First-generation sedating antihistamines (like chlorpheniramine or promethazine) can suppress cough and are particularly useful for nocturnal cough due to sedative effects 2, 4
• Menthol inhalation provides acute but short-lived relief 2, 3
• Avoid codeine and pholcodine - they have no greater efficacy than dextromethorphan but significantly more adverse effects (drowsiness, nausea, constipation, physical dependence) 2, 3

Wet/Productive Cough Management

Key Principle

• Cough suppression is not logical when patients are coughing up significant quantities of sputum - the cough serves a physiological purpose to clear mucus from the bronchial tree 1

Expectorant Use

• Guaifenesin is the standard expectorant used to loosen and relieve chest congestion in productive cough 5
• Dosing: 100 mg/5 mL oral solution, typically administered as directed on product labeling 5

What NOT to Use for Wet Cough

• Do not prescribe expectorants, mucolytics, antihistamines, or bronchodilators for uncomplicated acute lower respiratory tract infections, as consistent evidence for beneficial effects is lacking 1
• Avoid dextromethorphan and other antitussives for productive cough where clearance of secretions is beneficial 3, 4

Clinical Algorithm for Cough Syrup Selection

Step 1: Characterize the Cough

• Dry, non-productive cough → Consider antitussive therapy
• Wet, productive cough with sputum → Avoid suppression; consider expectorant only if needed

Step 2: For Dry Cough

• Try honey and lemon first 2, 3
• If inadequate relief: Dextromethorphan 30-60 mg for daytime use 2, 3
• If nocturnal cough disrupts sleep: Add first-generation antihistamine 2, 4

Step 3: For Wet Cough

• Reassure patient that cough is protective 1
• If chest congestion is bothersome: Guaifenesin may be tried, though evidence for benefit is limited 1, 5
• Focus on treating underlying cause rather than suppressing cough 1

Critical Pitfalls to Avoid

• Using subtherapeutic doses of dextromethorphan (standard OTC doses may be insufficient) 2, 3
• Suppressing productive cough with antitussives when secretion clearance is needed 1, 3
• Prescribing codeine-based products which offer no advantage over dextromethorphan but have worse side effects 2, 3
• Continuing antitussive therapy beyond 3 weeks without full diagnostic workup for persistent cough 3
• Missing serious underlying conditions - assess for pneumonia (fever, tachycardia, tachypnea, abnormal chest exam), hemoptysis, or foreign body before treating symptomatically 2