What is the recommended dose of dextromethorphan (cough suppressant) for adults and children?

Dextromethorphan Dosing for Cough Suppression

Recommended Adult Dosing

For adults requiring cough suppression, use dextromethorphan 30-60 mg every 12 hours, as standard over-the-counter doses are typically subtherapeutic and maximum cough reflex suppression occurs at 60 mg. 1

Adult Dosing Details:

• Standard dose: 10 mL (30 mg) every 12 hours, not exceeding 20 mL (60 mg) in 24 hours 2
• Optimal therapeutic dose: 60 mg provides maximum cough reflex suppression and can provide prolonged relief 3, 1
• Typical OTC dosing range: 10-30 mg three to four times daily, with maximum daily dose of 120 mg 3
• The FDA-approved dosing is often subtherapeutic; clinical guidelines suggest higher individual doses (up to 60 mg) are more effective 1

Important Adult Considerations:

• Dextromethorphan has a superior safety profile compared to codeine-based antitussives, with fewer adverse effects 1
• Do not use for productive cough where secretion clearance is beneficial 1
• Some combination preparations contain other ingredients like acetaminophen; exercise caution with higher doses 3, 1
• A single dose of 120 mg does not impair driving performance 4

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Recommended Pediatric Dosing

For children, use age-based FDA-approved dosing: ages 6-11 years receive 5 mL (15 mg) every 12 hours; ages 4-5 years receive 2.5 mL (7.5 mg) every 12 hours; do not use in children under 4 years. 2

Pediatric Dosing by Age:

• Ages 12+ years: 10 mL (30 mg) every 12 hours, not exceeding 20 mL in 24 hours 2
• Ages 6-11 years: 5 mL (15 mg) every 12 hours, not exceeding 10 mL in 24 hours 2
• Ages 4-5 years: 2.5 mL (7.5 mg) every 12 hours, not exceeding 5 mL in 24 hours 2
• Under 4 years: Do not use 2

Weight-Based Considerations:

• FDA age-based dosing results in variable weight-adjusted doses ranging from 0.35-0.94 mg/kg 5
• Research suggests 0.5 mg/kg may optimize symptom relief while minimizing adverse events, though this is not FDA-approved 5
• Medium doses (0.45-0.60 mg/kg) and higher doses (0.60-0.94 mg/kg) showed trends toward better symptom control than lower doses (0.35-0.45 mg/kg), though differences were not statistically significant 5

Pediatric Efficacy Evidence:

• Multiple-dose dextromethorphan reduced total 24-hour cough counts by 21% and daytime cough frequency by 25.5% compared to placebo in children ages 6-11 years 6
• Effects were most pronounced during daytime hours; nighttime cough rates showed minimal treatment differences 6
• Both objective cough monitoring and subjective parent-reported assessments showed statistically significant improvements 6

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Clinical Algorithm for Use

Step 1: Consider Non-Pharmacologic Options First

• Simple home remedies like honey and lemon may be equally effective as pharmacologic treatments for benign viral cough 1
• Voluntary cough suppression techniques can reduce cough frequency in some patients 1

Step 2: Assess Cough Characteristics

• Productive cough: Do not use dextromethorphan; secretion clearance is beneficial 1
• Dry, non-productive cough: Appropriate for dextromethorphan therapy 1
• Nocturnal cough: Consider sedating first-generation antihistamines as alternative 1

Step 3: Initiate Dextromethorphan at Appropriate Dose

• Use higher end of dosing range (30-60 mg for adults, age-appropriate doses for children) rather than minimal OTC doses 1
• Administer every 12 hours as per FDA labeling 2
• For short-term symptomatic relief only 1

Step 4: Consider Alternatives if Inadequate Response

• Menthol inhalation: Provides acute but short-lived relief 1
• For postinfectious cough: Try inhaled ipratropium before central antitussives 1
• For severe paroxysms: Consider prednisone 30-40 mg daily for short period 1
• Avoid codeine: No greater efficacy than dextromethorphan but significantly more adverse effects 1

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Critical Warnings and Contraindications

Drug Interactions:

• Dextromethorphan/quinidine combination: Use with extreme caution in older adults due to increased fall risk and drug interactions 7
• This combination has limited efficacy in behavioral symptoms of dementia without pseudobulbar affect 7

Special Populations:

• Elderly patients: Standard dextromethorphan monotherapy dosing applies, but avoid combination products with quinidine 7
• Children under 4 years: Contraindicated per FDA labeling 2

Common Pitfalls to Avoid:

• Using subtherapeutic doses that provide inadequate relief 1
• Prescribing for productive cough where mucociliary clearance is needed 1
• Choosing codeine-based products which have no efficacy advantage but increased side effects (drowsiness, nausea, constipation, physical dependence) 1
• Overlooking that combination products may contain acetaminophen or other ingredients when using higher doses 3, 1