Mucinex Fast Max DM Dosing Guide
For adults and children 12 years and older, the recommended dose is 10 mL every 12 hours, not exceeding 20 mL in 24 hours. 1
Age-Based Dosing
The FDA-approved dosing for dextromethorphan-containing products (which includes Mucinex Fast Max DM) is stratified by age:
- Adults and children ≥12 years: 10 mL every 12 hours (maximum 20 mL per 24 hours) 1
- Children 6 to under 12 years: 5 mL every 12 hours (maximum 10 mL per 24 hours) 1
- Children 4 to under 6 years: 2.5 mL every 12 hours (maximum 5 mL per 24 hours) 1
- Children under 4 years: Do not use 1
Administration Instructions
- Shake the bottle well before each use 1
- Use only the dosing cup provided with the product - do not substitute with other measuring devices 1
- Do not use the provided dosing cup with other products to avoid dosing errors 1
Important Safety Considerations
Abuse potential: Dextromethorphan is subject to abuse, particularly among adolescents who may take megadoses (5-10 times the recommended dose) to achieve intoxicating effects similar to phencyclidine (PCP) 2. The drug is easily accessible over-the-counter, making it a target for misuse 2.
Genetic variability: Approximately 5% of individuals of European ethnicity lack the ability to metabolize dextromethorphan normally, which can lead to rapid accumulation of toxic levels even at recommended doses 2.
Combination product toxicity: Mucinex Fast Max DM contains both dextromethorphan and guaifenesin, and overdose toxicity is additive when multiple active ingredients are present 2.
Clinical Context
The guaifenesin component (expectorant) has a well-established safety profile in adults and pediatric populations, with typical dosing ranges of 200-400 mg every 4 hours (up to 6 times daily for immediate-release formulations) 3. Extended-release formulations like this product provide convenience with 12-hourly dosing 3. The most common adverse events with guaifenesin are mild gastrointestinal and nervous system effects 4.