What is the recommended dose and route of administration for dextromethorphan (cough suppressant) and Ascoril D (dextromethorphan) syrup?

Dextromethorphan Dosing and Administration

For adults with acute cough, dextromethorphan should be dosed at 30-60 mg orally three to four times daily (maximum 120 mg/24 hours), as standard over-the-counter doses of 10-15 mg are subtherapeutic and maximum cough suppression occurs at 60 mg. 1, 2

Route of Administration

• Dextromethorphan is administered orally as a syrup or liquid formulation 3
• The bottle should be shaken well before use and measured only with the provided dosing cup 3

Standard Dosing by Age

Adults and Children ≥12 Years

• 10 mL every 12 hours (per FDA labeling), not to exceed 20 mL in 24 hours 3
• However, guideline-based dosing for optimal efficacy is 10-15 mg three to four times daily, with maximum cough reflex suppression at 60 mg doses 1
• The maximum daily dose should not exceed 120 mg/day 1

Children 6 to <12 Years

• 5 mL every 12 hours, not to exceed 10 mL in 24 hours 3

Children 4 to <6 Years

• 2.5 mL every 12 hours, not to exceed 5 mL in 24 hours 3

Children <4 Years

• Do not use 3

Ascoril D Syrup Specifics

Ascoril D contains dextromethorphan as the antitussive component. The dosing follows the same principles as dextromethorphan monotherapy, but caution is required with combination preparations as they contain additional ingredients (such as paracetamol or other compounds) that may limit the ability to increase dextromethorphan to therapeutic doses without exceeding safe limits of the other components. 2

Critical Dosing Considerations

The Subtherapeutic Dosing Problem

• Standard over-the-counter dosing (15-30 mg) is often inadequate for optimal cough suppression 2, 4
• Maximum cough reflex suppression occurs at 60 mg and can be prolonged at this dose 1, 2, 4
• Studies show a dose-response relationship, with better symptom control at 0.5 mg/kg dosing 5

When to Use Dextromethorphan

• First-line agent for non-productive (dry) cough due to superior safety profile compared to opioid alternatives 2, 4
• Should NOT be used for productive cough where clearance of secretions is beneficial 2, 4
• Consider only after simple remedies like honey and lemon have been tried 2, 4

Duration of Treatment

• Limit to short-term use, typically less than 7 days 4
• If no improvement after a short course, discontinue and try another approach 1

Common Pitfalls to Avoid

• Using subtherapeutic doses: The typical 10-15 mg dose may provide minimal relief; consider 30-60 mg for adequate suppression 2, 4
• Combination product overdose: When using higher dextromethorphan doses in combination products, monitor total daily intake of other ingredients like paracetamol to avoid toxicity 2
• Using for productive cough: Dextromethorphan suppresses the cough reflex and should be avoided when secretion clearance is needed 2
• Prolonged use: If symptoms persist beyond 7 days, reassess for underlying causes rather than continuing antitussive therapy 4

Alternative Considerations

For Nocturnal Cough

• First-generation sedating antihistamines (like promethazine) can be added specifically for nighttime cough due to sedative properties 2, 4

For Refractory Cough

• Inhaled ipratropium should be tried before central antitussives for postinfectious cough 2, 4
• Short-course prednisone (30-40 mg daily) may benefit severe paroxysms of postinfectious cough 2, 4

Safety Profile

• Dextromethorphan has superior safety compared to codeine, with fewer adverse effects and no greater efficacy disadvantage 2, 6
• At directed doses, dextromethorphan is safe and effective, though abuse at very high doses (>1500 mg/day) can cause psychosis 7