Taking Promethazine With Codeine With NyQuil

In our latest question and answer, the pharmacist discusses whether or not it is safe to promethazine with codeine and NyQuil at the same time.


I took 5ml of promethazine w/ codeine. Can I take a dose of NyQuil with it?

Asked by Sweet A On Oct 26, 2022

Answered by
Medical Content Reviewed By HelloPharmacist Staff

Published Oct 26, 2022
Last updated Oct 26, 2022

Key points

  • Combining Promethazine with codeine and NyQuil should generally be avoided due to the risk of additive side effects.


It is generally not recommended to take promethazine with codeine and NyQuil together, for numerous reasons.

Both Drugs Contain Antihistamines

First and foremost, NyQuil contains the antihistamine doxylamine, which is similar to Benadryl in that it is classified as a sedating "first-generation" antihistamine.

Promethazine is also an antihistamine, with very similar effects to doxylamine, and may even be more sedating for some individuals.

Promethazine with doxylamine represents a double dose of sedating antihistamines and is considered a duplicate therapy. You will likely feel drowsy or more tired when taking these drugs together. In addition, you may experience other side effects including:

  • Constipation
  • Dizziness
  • Difficulty with urination
  • Dry mouth and eyes
  • Changes in vision
  • Fast heartbeat
  • Confusion

Combining Codeine With Multiple Antihistamines Increases The Risk Of Side Effects

Not only will taking two different antihistamines likely cause some of the side effects mentioned in the section above, promethazine with codeine, of course, contains codeine. Adding on the doxylamine from NyQuil will further increase the risk of serious side effects, such as respiratory depression.

Final Words

Last but not least, both promethazine and codeine and NyQuil contain alcohol. While it isn't much alcohol, you still would be combining three drugs (i.e., doxylamine, promethazine, and ethanol) that are considered CNS (central nervous system) depressants.

The drugs should be avoided with one another unless your doctor has directed you otherwise.

Although the duration of action of these drugs can vary by individual, each lasts around 4 to 6 hours and should be separated by at least that amount of time.

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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 Hello@HelloPharmacist.com! You can also connect with Dr. Brian Staiger on LinkedIn.

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