Is it safe to take Nyquil (dextromethorphan and acetaminophen) and tizanidine together?

Concomitant Use of Nyquil and Tizanidine

Taking Nyquil (containing dextromethorphan and acetaminophen) together with tizanidine is not recommended due to the risk of additive central nervous system depression, which could lead to excessive sedation, dizziness, and potentially dangerous respiratory depression.

Mechanism of Interaction

The primary concern with this combination stems from the additive central nervous system (CNS) depressant effects:

• Tizanidine is an α2-adrenergic receptor agonist muscle relaxant with significant sedative properties 1
• Nyquil contains dextromethorphan (a cough suppressant) and acetaminophen (a pain reliever), along with other ingredients that can cause drowsiness
• The FDA label for tizanidine specifically warns that "sedation may be additive when tizanidine is taken in conjunction with drugs or substances that act as CNS depressants" 2

Specific Risks

CNS Depression

• Both medications can cause significant drowsiness and sedation
• Combined use increases the risk of:
  • Excessive sedation
  • Impaired coordination
  • Dizziness
  • Confusion
  • Potentially dangerous respiratory depression

Cardiovascular Effects

• Tizanidine can cause hypotension and bradycardia 2, 3
• This effect could be worsened by ingredients in some Nyquil formulations

Functional Impairment

• The combination would significantly impair ability to:
  • Drive vehicles
  • Operate machinery
  • Perform tasks requiring alertness 2

Special Considerations

High-Risk Groups

• Elderly patients are at particularly high risk due to:

  • Decreased drug clearance (tizanidine clearance is reduced four-fold in elderly) 2
  • Increased sensitivity to CNS depressant effects

• Patients with renal or hepatic impairment:

  • Tizanidine clearance is reduced by more than 50% in renal insufficiency 2
  • Both drugs may accumulate to toxic levels

Alcohol Content

• Some Nyquil formulations contain alcohol
• Alcohol increases tizanidine AUC by approximately 20% while also increasing its Cmax by approximately 15% 2
• This further increases the risk of adverse effects

Alternative Approaches

If you need relief from symptoms that Nyquil would address while taking tizanidine:

1. For pain relief: Consider acetaminophen alone (without the other Nyquil ingredients)
2. For cough: Consider non-sedating cough suppressants after consulting with your healthcare provider
3. For congestion: Consider non-sedating decongestants if not contraindicated by other medical conditions

Conclusion

The combination of Nyquil and tizanidine poses significant risks due to additive CNS depression. The potential for excessive sedation, impaired coordination, and respiratory depression makes this combination potentially dangerous. Alternative approaches for symptom management should be discussed with your healthcare provider.