What is the recommended dose of Copastin (dextromethorphan) in tablet form?

Recommended Dose of Dextromethorphan in Tablet Form

For adults and children 12 years and older, the recommended dose is 30 mg every 12 hours, not exceeding 60 mg in 24 hours, though clinical evidence suggests 60 mg provides optimal cough suppression. 1, 2

Standard FDA-Approved Dosing by Age

The FDA-approved dosing for dextromethorphan oral formulations is: 2

• Adults and children ≥12 years: 10 mL (30 mg equivalent) every 12 hours, maximum 20 mL (60 mg) in 24 hours 2
• Children 6 to <12 years: 5 mL (15 mg equivalent) every 12 hours, maximum 10 mL (30 mg) in 24 hours 2
• Children 4 to <6 years: 2.5 mL (7.5 mg equivalent) every 12 hours, maximum 5 mL (15 mg) in 24 hours 2
• Children <4 years: Do not use 2

Evidence-Based Optimal Dosing

Standard over-the-counter dosing is often subtherapeutic; maximum cough reflex suppression occurs at 60 mg and can be prolonged. 1 Clinical evidence demonstrates: 1

• 60 mg provides optimal cough suppression with superior efficacy compared to lower doses 1
• Standard 30 mg doses may provide modest reduction in cough (19-36%) but are frequently inadequate 1
• The dose-response relationship shows increasing benefit up to 60 mg 1

Weight-Based Dosing Considerations for Children

Research suggests weight-based dosing may be more appropriate than age-based dosing: 3

• Low dose: 0.35 to <0.45 mg/kg per dose 3
• Medium dose: 0.45 to <0.60 mg/kg per dose 3
• High dose: 0.60-0.94 mg/kg per dose 3

A dose of 0.5 mg/kg may balance symptomatic relief with avoidance of adverse events in pediatric patients. 3 However, adverse events occurred most frequently in the high-dose group (0.60-0.94 mg/kg). 3

Important Safety Considerations

• Caution with higher doses: Some combination preparations contain other ingredients like acetaminophen that could lead to toxicity at higher dextromethorphan doses 1
• Do not use for productive cough where clearance of secretions is beneficial 1, 4
• Toxic threshold: Blood concentrations exceeding 100 ng/mL can be toxic in young children, with a 71.4 mg/kg ingestion causing life-threatening symptoms requiring intubation 5
• Drug interactions: Use with caution in elderly patients, particularly when combined with quinidine due to increased fall risk and drug interactions 4

Clinical Algorithm for Tablet Dosing

For adults seeking cough suppression: 1

• Start with 30 mg every 12 hours (standard FDA dose) 2
• If inadequate relief, increase to 60 mg every 12 hours (maximum daily dose) 1, 2
• Do not exceed 60 mg in 24 hours 2

For children 6-11 years: 2

• Use 15 mg every 12 hours (standard dose) 2
• Maximum 30 mg in 24 hours 2
• Consider weight-based dosing of 0.5 mg/kg for better efficacy if standard dosing inadequate 3

For children 4-5 years: 2

• Use 7.5 mg every 12 hours 2
• Maximum 15 mg in 24 hours 2

Common Pitfalls to Avoid

• Using subtherapeutic doses: The standard 30 mg dose may not provide adequate relief; 60 mg is often needed for optimal effect 1
• Exceeding maximum daily doses: Do not exceed FDA-recommended maximum doses, particularly in combination products 1, 2
• Ignoring contraindications: Avoid in productive cough where secretion clearance is needed 1, 4
• Age-based dosing in children: Consider weight-based dosing (0.5 mg/kg) for more consistent therapeutic effect 3