Can You Take Adipex-P (Phentermine) With Cold Medicine?
Some cold medications are safe with phentermine, but some should be used with caution or avoided altogether.
I've been taking Adipex-P for two months now and this morning I woke up with the beginning of a cold. What cough medications can I take that are safe for me? Also, are there daytime medications that I can take? Thank you.
Sep 27, 2022- Phentermine can interact with common cold medicines like dextromethorphan, pseudoephedrine, and phenylephrine, so you should ask your doctor before using them together. Safe alternatives for cold symptoms while taking phentermine include antihistamines, pain relievers like Tylenol or Advil, and expectorants like Mucinex. Always read the labels on over-the-counter cold products since they often contain ingredients that interact with phentermine.
Answer
Phentermine (Adipex-P) has several interactions with over-the-counter cough/cold medications that are important to be aware of.
Specifically, caution needs to be taken before combining phentermine with:
- Dextromethorphan (cough suppressant)
- Pseudoephedrine (nasal decongestant)
- Phenylephrine (nasal decongestant)
We discuss these in more detail below.
Cold Medications To Use Cautiously
Phentermine With Dextromethorphan
Both phentermine and dextromethorphan can increase levels of the neurotransmitter serotonin. This increases the risk of a rare but serious condition known as serotonin syndrome, which is characterized by several symptoms, including:
- Agitation
- Anxiety
- Hyperthermia
- Mental status changes
- Cognitive impairment
- Seizures
- Rigidity
- Sweating
- Nausea
- Vomiting
While the overall risk of serotonin is relatively low for most individuals, combining medications with serotonin effects increases the risk.
There is some controversy regarding how strong an effect dextromethorphan has on serotonin. Some studies show that when taken at recommended doses, it doesn't increase levels.
Other studies however have presented case reports in which serotonin syndrome occurred on usual doses. It is important to speak with your doctor before combining phentermine with dextromethorphan.
It is also important to be aware that dextromethorphan is a very common ingredient in over-the-counter cough/cold medications. For example, it is included in NyQuil, DayQuil, and Tylenol Cold & Flu. Be sure to read the labels of the over-the-counter products you plan on purchasing.
Phentermine With Pseudoephedrine Or Phenylephrine
Taking phentermine with pseudoephedrine or phenylephrine can increase blood pressure and heart rate.
Phentermine is a stimulant medication, chemically similar to amphetamines. Both pseudoephedrine and phenylephrine have mild stimulating properties. Taking phentermine with a nasal decongestant can have additive effects.
Phentermine should not be used with either drug unless specifically directed by your doctor.
What Cold Medications Are Safe?
While you should avoid any of the medications previously discussed with phentermine unless you speak with your doctor, the following are considered to have no drug interactions:
Antihistamines
Antihistamines are considered safe to take with phentermine. While not often classified as 'cold' medications, antihistamines can help many related symptoms, including:
- Runny nose
- Congestion
- Watery eyes
- Postnasal drip (which could cause a cough)
- Insomnia (with sedating antihistamines like Benadryl)
Over-the-counter antihistamines include:
- Benadryl (sedating)
- Zyrtec
- Allegra
- Claritin
Pain Relievers
Both NSAID pain relievers (e.g. Advil, Aleve) and Tylenol (acetaminophen) are considered safe with phentermine. They can provide symptomatic relief for a variety of cold symptoms, including fever and headaches.
Expectorants
Mucinex (guaifenesin) is considered safe to use with phentermine. Mucinex helps to relieve chest congestion and can be helpful for post-nasal drip.
Other
Most "natural" products for cough relief are safe to use, including ones with honey. In addition, cough drops with menthol or ones with anesthetics (e.g. benzocaine) are considered safe.
Final Words
I hope this answer provided some assistance and please reach back out again if anything comes up!
References & sources
Glossary — Terms in This Answer
- Neurotransmitter
- A chemical messenger in the brain that transmits signals between nerve cells.
- Serotonin syndrome
- A rare but serious condition caused by too much serotonin activity in the body, leading to symptoms like agitation, confusion, and muscle rigidity.
- Stimulant medication
- A drug that increases activity in the nervous system and raises alertness and energy.
- Additive effects
- When two drugs combine to produce a stronger total effect than either drug would produce alone.
- Antihistamines
- Medications that block the effects of histamine in the body to relieve allergy and cold symptoms.
- NSAID
- Non-steroidal anti-inflammatory drugs, a class of pain relievers that reduce inflammation and fever.
- Expectorant
- A medication that helps thin and loosen mucus to make it easier to cough up.
- Drug interactions
- Unwanted changes that occur when two or more medications are taken together and affect how each other works in the body.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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