Can an overdose of DayQuil (dextromethorphan) and NyQuil (acetaminophen, dextromethorphan, doxylamine) cause altered mental status?

DayQuil and NyQuil Overdose Can Cause Significant Altered Mental Status

Yes, an overdose of DayQuil and NyQuil can cause altered mental status due to their active ingredients, particularly dextromethorphan and doxylamine, which can produce anticholinergic effects, delirium, hallucinations, and other neurological symptoms.

Active Ingredients and Mechanisms

DayQuil and NyQuil contain several active ingredients that can affect mental status when taken in excessive amounts:

1. Dextromethorphan (DXM)

   • Present in both DayQuil and NyQuil
   • At high doses, acts as an NMDA receptor antagonist
   • Can cause dissociative effects, hallucinations, and altered perception

2. Doxylamine succinate

   • Present in NyQuil
   • First-generation antihistamine with strong anticholinergic properties
   • Can cause significant central nervous system effects in overdose

3. Acetaminophen

   • Present in both products
   • While primarily hepatotoxic in overdose, severe hepatic injury can lead to encephalopathy

Clinical Manifestations of Overdose

Anticholinergic Effects (Primarily from Doxylamine)

• Confusion and disorientation
• Agitation and delirium
• Visual hallucinations
• Slurred speech 1
• Mydriasis (pupillary dilation)
• Dry mucous membranes
• Tachycardia
• Hyperthermia
• Urinary retention

The classic presentation of anticholinergic toxicity is often described as: "Hot as a hare, blind as a bat, dry as a bone, red as a beet, mad as a hatter" 2.

Dextromethorphan Toxicity

• Altered mental status ranging from mild confusion to severe agitation
• Hallucinations and perceptual distortions
• Ataxia
• Nystagmus
• Hypertension
• Tachycardia

Severe Complications

• Seizures 3
• Rhabdomyolysis 4
• Serotonin syndrome (particularly if combined with other serotonergic medications) 2
• Respiratory depression

Risk Factors for Severe Toxicity

• Concomitant use of other central nervous system depressants (especially benzodiazepines) 2
• Older age (particularly for doxylamine toxicity) 5
• Combination with serotonergic medications
• Liver or kidney dysfunction
• Intentional misuse for recreational purposes

Management of Overdose

1. Supportive Care

   • Airway management and respiratory support
   • Intravenous fluids
   • Cardiac monitoring

2. Decontamination

   • Activated charcoal may be considered if presentation is within 1 hour of ingestion

3. Specific Interventions

   • For anticholinergic toxicity: Physostigmine may be considered in severe cases 2
   • For seizures: Benzodiazepines are first-line therapy
   • For serotonin syndrome: Benzodiazepines and serotonin antagonists (e.g., cyproheptadine) 2

4. Monitoring

   • Continuous cardiac monitoring
   • Frequent neurological assessments
   • Liver function tests (for acetaminophen toxicity)
   • Creatine kinase levels (for rhabdomyolysis)

Prevention and Education

• Public education about the risks of exceeding recommended doses
• Recognition that over-the-counter medications can cause serious toxicity
• Awareness that older adults are particularly susceptible to anticholinergic effects 5
• Contact poison control center (1-800-222-1222 in the US) for guidance in cases of suspected overdose 2

Important Considerations

• The combination of DayQuil and NyQuil increases the risk of toxicity due to duplicate ingredients
• False positive urine drug screens for methadone have been reported with doxylamine overdose 3
• Rhabdomyolysis can be a delayed complication of doxylamine overdose 4
• Patients with altered mental status from these medications may require prolonged observation due to the long half-life of some components

In summary, overdose of DayQuil and NyQuil should be considered in the differential diagnosis of patients presenting with unexplained altered mental status, particularly when accompanied by anticholinergic features or signs of serotonergic excess.