Can You Take Phentermine With NyQuil?

In our latest question and answer, the pharmacist discusses whether or not phentermine (Adipex-P) can be taken with NyQuil.


Can you take phentermine in morning and NyQuil at night?

Asked by Momof3 On Jan 31, 2018

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Jan 31, 2018

Phentermine (brand name Adipex-P) and NyQuil may be used together as there is no listed or reported interaction between the two. However, using both together could lessen the effect of both medications as discussed below.

Phentermine - NyQuil Information

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

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

Phentermine is a sympathomimetic medication, chemically similar to amphetamines and is used for the treatment of obesity.

While there is no interaction between NyQuil and phentermine, they do have conflicting effects. Phentermine can have amphetamine-like effects and is a CNS (central nervous system) stimulant. These effects include:

  • Increased concentration
  • Increased attentiveness
  • Restlessness
  • Over-stimulation

NyQuil contains doxylamine, a sedating antihistamine. Although there is no drug-drug interaction, the sedatory effects of NyQuil may be decreased due to the stimulant action of phentermine. Similarly, the stimulatory effects of phentermine may be decreased if used with NyQuil.

If you are looking to avoid the conflicting effects of both medications, try to space them as far apart as possible. The duration of action of phentermine varies, but can last anywhere from 12-16 hours. The effects of NyQuil generally last around 4 to 6 hours.

About the Pharmacist

Dr. Brian Staiger Pharm.D

Dr. Brian Staiger is a licensed pharmacist in New York State and the founder of He graduated from the University At Buffalo with a Doctor of Pharmacy degree in 2010. He has been featured in numerous publications including the Huffington Post as well as a variety of health and pharmacy-related blogs. Please feel free to reach out to him directly if you have any inquiries or want to connect! He's answered thousands of medication and pharmacy-related questions and he's ready to answer yours! Office: 716-389-3076

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