Taking NyQuil With Allegra

In our latest question and answer, the pharmacist discusses whether or not NyQuil can safely be taken with the antihistamine Allegra (fexofenadine).

Question

I take Allegra every morning for my allergies. I am wondering if it is okay to take NyQuil once and a while at night to help sleep?

Asked by Michael On May 12, 2022

Answered by
Medical Content Reviewed By HelloPharmacist Staff

Published May 12, 2022
Last updated Mar 29, 2024

Key points

  • Allegra contains fexofenadine, an anhistamine. NyQuil contains doxylamine, another antihistamine.
  • A general rule of thumb is to not combine drugs that are in the same class (e.g. antihistamines in this case).
  • Combining Allegra and NyQuil could increase the risk and severity of side effects, such as sedation.
  • Even though you may experience some side effects, such as excessive drowsiness, there isn't thought the be a significant risk in combining Allegra and NyQuil once in awhile.
  • If you do plan on taking Allegra and NyQuil on the same day, it is best just not to take them at the same time (i.e. separate them by a few hours at least).

Overview

In the vast majority of individuals, it is safe to take Allegra (fexofenadine) the same day as NyQuil, even though Allegra is an antihistamine and NyQuil contains an antihistamine.

However, they generally should not be taken at the same time.

At the very least, they should be separated from one another by at least four to six hours to decrease the risk of excess sedation and drowsiness.

Allegra is essentially non-drowsy on its own, but it is a general rule of thumb to not combine two drugs in the same medication class (unless otherwise directed to do so by your doctor).

Interaction Details

Allegra (fexofenadine) is a "second generation" antihistamine and has a duration of action of around 24 hours.

Most second-generation antihistamines do not cause drowsiness or sedation, including Allegra.

While Allegra doesn't cause drowsiness on its own, it can still increase the risk of sedation when used with other sedating medications.

NyQuil is a combination ingredient cough/cold medication and contains the following active ingredients:

  • Acetaminophen (analgesic)
  • Dextromethorphan (cough suppressant)
  • Doxylamine (sedating antihistamine)

Doxylamine, like Allegra, is an antihistamine but is classified as a "first-generation" antihistamine.

First-generation antihistamines are characterized by their short duration of action (~4 to 6 hours) and their sedative effects.

While doxylamine is effective for the treatment of allergy symptoms, it is most often used in over-the-counter products as a sleep aid.

The concern with using NyQuil and Allegra at the same time is the potential for additive antihistamine side effects from each, which potentially includes:

  • Drowsiness
  • Constipation
  • Dry mouth
  • Dry eyes
  • Sedation

Final Words

Summing things up, as mentioned, Allegra should not be taken at the same time as NyQuil due to the additive sedative effects.

However, if you take Allegra in the morning for your allergy symptoms and you tolerate it well, you can certainly take NyQuil safely in the evening to help with cough/cold symptoms and for problems falling asleep.

References

About the Pharmacist

Dr. Brian Staiger, PharmD

Dr. Brian has been practicing pharmacy for over 13 years and has wide-ranging experiences in many different areas of the profession. From retail, clinical, program development, and administrative responsibilities, he's your knowledgeable and go-to source for all your pharmacy and medication-related questions! Dr. Brian Staiger also has herbalist training and educational certificates in the field of medical ethnobotany. Feel free to send him an email at [email protected]! You can also connect with Dr. Brian Staiger on LinkedIn.

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