Will the Child Be Drowsy in the Morning?
Yes, the child may experience drowsiness in the morning after receiving 10 ml of Robitussin (dextromethorphan), though the evidence for dextromethorphan's efficacy is poor and it is not recommended for children with upper respiratory infections.
Important Context About This Medication
The most critical issue here is not just morning drowsiness, but that dextromethorphan should not be used in young children at all. The American Academy of Pediatrics recommends that OTC cough and cold medications generally should be avoided in all children below 6 years of age due to lack of efficacy and potential toxicity 1. Between 1969 and 2006, there were multiple fatalities associated with OTC cough and cold medications in young children, with drug overdose and toxicity being common events 1.
Drowsiness Risk Assessment
Morning drowsiness is possible but unpredictable:
- Dextromethorphan itself has been associated with insomnia more frequently than drowsiness in pediatric studies 2
- However, many Robitussin formulations contain first-generation antihistamines (like diphenhydramine or chlorpheniramine) as combination ingredients, which are strongly associated with next-day sedation 1
- First-generation antihistamines dosed only at bedtime can be associated with significant daytime drowsiness, decreased alertness, and performance impairment because these medications and their metabolites have prolonged plasma half-lives, and their end-organ effects persist longer than plasma levels of the parent compound 1
- Performance impairment can exist without subjective awareness of drowsiness—meaning the child may not appear drowsy but still have cognitive and motor impairment 1
What to Monitor
Watch for these signs in the morning:
- Excessive sleepiness or difficulty waking 1
- Decreased alertness or "foggy" behavior 1
- Paradoxical CNS stimulation (hyperactivity, irritability) can also occur with these medications, particularly in children 1
- Anticholinergic effects including dry mouth, constipation, or urinary retention 1
The Bigger Problem: Lack of Efficacy
The medication likely won't help the cough anyway:
- Multiple high-quality studies show that dextromethorphan is not superior to placebo for nocturnal cough and sleep difficulty in children with upper respiratory infections 2
- A dose-response study found no statistically significant differences in cough relief across different doses of dextromethorphan in children 3
- The American Academy of Pediatrics does not support the use of dextromethorphan for treating acute cough in children 3, 4
- Controlled trials have shown that antihistamine-decongestant combination products are not effective for symptoms of upper respiratory tract infections in young children 1
What Should Have Been Done Instead
Evidence-based supportive care for URI includes:
- Adequate hydration to thin secretions 5
- Age-appropriate antipyretics (acetaminophen or ibuprofen) for fever and comfort 5
- Gentle nasal suctioning to improve breathing 5
- Honey (for children over 1 year) has been shown to be an effective antitussive 6
- Topically applied vapor rubs may be effective 6
When to Seek Immediate Care
Call for urgent evaluation if the child develops:
- Respiratory rate >50 breaths/min 5
- Difficulty breathing, grunting, or cyanosis 5
- Oxygen saturation <92% 5
- Not feeding well or signs of dehydration 5
- Persistent high fever ≥39°C for 3+ consecutive days 5
Moving Forward
For future URIs, avoid OTC cough and cold medications in children under 6 years 1, 5. The typical course of viral URI lasts 5-7 days with symptoms peaking between days 3-6, and supportive care alone is appropriate 5, 7. Only consider antibiotics if bacterial sinusitis criteria are met (symptoms ≥10 days without improvement, worsening after initial improvement, or severe onset with high fever and purulent discharge for 3-4 consecutive days) 5, 7.