Robafen (Dextromethorphan) Cough Syrup: Dosing and Usage
For adults and children 12 years and older, the standard dose of Robafen (dextromethorphan) is 10 mL every 12 hours, not exceeding 20 mL in 24 hours, though clinical evidence shows maximum cough suppression occurs at 60 mg (20 mL), which is higher than typical over-the-counter dosing. 1, 2
Standard FDA-Approved Dosing
Adults and children ≥12 years:
- 10 mL every 12 hours
- Maximum: 20 mL in 24 hours 1
Children 6 to under 12 years:
- 5 mL every 12 hours
- Maximum: 10 mL in 24 hours 1
Children 4 to under 6 years:
- 2.5 mL every 12 hours
- Maximum: 5 mL in 24 hours 1
Children under 4 years:
- Do not use 1
Clinical Considerations for Optimal Efficacy
The British Thoracic Society notes that standard over-the-counter dosing is often subtherapeutic, with a clear dose-response relationship showing maximum cough reflex suppression at 60 mg. 2, 3 This means the maximum FDA-approved daily dose (20 mL = 60 mg if using standard 30 mg/10 mL formulation) may be needed for severe cough, though this should be given as a single dose rather than divided. 2
Important Safety Warning
When using higher doses, verify that your Robafen formulation does not contain additional ingredients like acetaminophen or guaifenesin, as these could reach toxic levels at higher dextromethorphan doses. 2, 3
When to Use Dextromethorphan
Appropriate indications:
- Dry, non-productive cough from viral upper respiratory infections 4
- Short-term symptomatic relief when cough interferes with daily activities or sleep 2
- Postinfectious cough only after other measures (like inhaled ipratropium) have failed 2
Do NOT use for:
- Productive cough where secretion clearance is beneficial 3
- Cough with signs of pneumonia (fever, tachypnea, tachycardia, abnormal chest exam) 2
- Cough lasting more than 3 weeks without diagnostic workup 3
First-Line Approach Before Medication
The British Thoracic Society recommends simple home remedies like honey and lemon as first-line treatment, which may be as effective as pharmacological options for benign viral cough. 4, 2 Voluntary cough suppression through central modulation may also reduce cough frequency without medication. 2
Alternative Options
For nocturnal cough disrupting sleep:
- First-generation antihistamines (like diphenhydramine) provide both cough suppression and sedation 2, 3
For quick but temporary relief:
What NOT to Use
Codeine and pholcodine have no greater efficacy than dextromethorphan but carry significantly more adverse effects including drowsiness, nausea, constipation, and physical dependence. 4, 2, 5 The British Thoracic Society explicitly recommends against these opioid alternatives. 4, 5
When to Seek Medical Attention
Stop self-treatment and see a physician if: 4
- Coughing up blood
- Breathlessness develops
- Prolonged fever and feeling unwell
- Pre-existing conditions (COPD, heart disease, diabetes, asthma)
- Recent hospitalization
- Symptoms persist beyond 3 weeks
Duration of Treatment
Dextromethorphan should be used for short-term symptomatic relief only. 3 If cough persists beyond 3 weeks, discontinue and pursue diagnostic workup for underlying causes rather than continued antitussive therapy. 3
Common Pitfalls to Avoid
- Using subtherapeutic doses that provide inadequate relief 2, 3
- Continuing treatment beyond 3 weeks without investigating underlying causes 3
- Using dextromethorphan for productive cough where secretion clearance is needed 3
- Failing to check for additional ingredients in combination products when using higher doses 2, 3