What is the recommended dosage and frequency of dextromethorphan (cough suppressant) for adults?

Recommended Dosage and Frequency of Dextromethorphan for Adults

For adults, the recommended dosage of dextromethorphan is 10-15 mg three or four times daily, with a maximum daily dose of 120 mg. 1

Standard Dosing Guidelines

• The FDA-approved dosage for adults and children 12 years and older is 10 mL every 12 hours, not to exceed 20 mL in 24 hours 2
• Clinical guidelines indicate a standard dosage of 10-15 mg three or four times daily, though some publications suggest 10-30 mg per dose 1
• The maximum recommended daily dose should not exceed 120 mg 1

Efficacy Considerations

• The generally recommended over-the-counter dosage is likely subtherapeutic according to research 1
• Maximum cough reflex suppression occurs at 60 mg and can be prolonged 1, 3
• A single 30 mg dose has shown limited efficacy in acute upper respiratory tract infection cough in some studies 4
• Dextromethorphan has been shown to reduce cough frequency at a dose of 20 mg, comparable to codeine 5

Administration Methods

• Dextromethorphan is available in many over-the-counter cough preparations 1
• When using liquid formulations, the bottle should be shaken well before use 2
• Measurement should only be done with the dosing cup provided with the medication 2

Important Precautions

• Care must be taken when using higher doses of dextromethorphan as some combined preparations contain other ingredients such as paracetamol 1, 3
• At inappropriately high doses (over 1500 mg/day), dextromethorphan can induce psychosis with PCP-like symptoms including delusions, hallucinations, and paranoia 6
• Dextromethorphan should not be used for productive cough as it may interfere with the beneficial clearing of secretions 7

Advantages Over Other Antitussives

• Dextromethorphan has no greater efficacy than codeine but has a much better side effect profile 1, 3
• It is considered non-sedating compared to other opiate antitussives 3
• Dextromethorphan has overtaken codeine as the most widely used cough suppressant due to its availability, efficacy, and safety profile at directed doses 6

Alternative Options

• For nocturnal cough, sedative antihistamines may be suitable but cause drowsiness 1
• Menthol by inhalation can provide acute but short-lived cough suppression 1, 7
• For viral acute cough, simple remedies like honey and lemon may be the most simple and economical option 3