Can You Take Benadryl With Nyquil?
Our pharmacist answers the latest question regarding whether or not you can take Benadryl (diphenhydramine) with Nyquil.
Can I take Benadryl (Diphenhydramine) and Nyquil together?
Aug 22, 2022- Both Benadryl and Nyquil contain sedating antihistamines that work the same way, so taking them together is not recommended as it increases the risk of excessive sedation and side effects like dry mouth, dry eyes, and constipation.
- If you need to take both medications, they can be taken on the same day as long as you separate doses by at least four to six hours since that is how long each medication lasts.
- In certain situations like an allergic reaction occurring after you've already taken Nyquil, taking Benadryl may be appropriate, but it's best to talk with your pharmacist or doctor about your specific situation.
Answer
In most cases, it is not recommended to take Benadryl (diphenhydramine) and Nyquil together since they both contain sedating antihistamines.
The sedating antihistamine in NyQuil is doxylamine, which is very closely related to diphenhydramine (the active ingredient in Benadryl). In fact, they are in the same class of medication, sedating first-generation antihistamines.
Taking two first-generation antihistamines together is considered 'duplicate therapy' and increases the risk of side effects occurring. In most cases, it would be recommended to just take one or the other.
What Is Benadryl?
Benadryl is classified as a first-generation antihistamine. The duration of action of the drug is typically 4-6 hours per dose (25 mg to 50 mg).
First-generation antihistamines are known for their sedative effects and CNS (central nervous system) depressant effects. Many individuals cannot tolerate the sedative effects of Benadryl (diphenhydramine) during the day and, therefore, only take it at bedtime to combat insomnia.
What Is NyQuil?
Nyquil is a combination cold/cough product that contains the drug doxylamine, along with a pain/fever reducer (acetaminophen) and a cough suppressant (dextromethorphan).
Doxylamine is a sedating first-generation antihistamine and is in the same class of medication as Benadryl (diphenhydramine).
Interaction Explained
As stated above, doxylamine and Benadryl (diphenhydramine) work the same way and are actually in the same class of medication.
They work by blocking the histamine-1 receptor in the body, which prevents histamine from binding to it and producing the symptoms we are all very familiar with (e.g. runny nose, watery eyes, etc...).
Since both drugs work the same way, using both at the same time is not recommended.
Combined use generally won't provide any more benefit than taking either alone. Additionally, taking them together not only increases the risk of excessive sedation, it greatly increases the risk of additional adverse effects such as:
- Dry mouth
- Dry eyes
- Constipation
- Constricted airways
Very high doses of sedating antihistamines have also been associated with excitation, agitation, and restlessness.
Is Use Together Ever Okay?
Having said that, there could be a case to take the combination together.
Benadryl (diphenhydramine) has fairly strong evidence for use in stemming allergic reactions.
Studies show that Benadryl (diphenhydramine) can effectively reduce itching and swelling from reactions to things like bee stings and poison ivy.
If you have already taken a dose of Nyquil and are having an allergic reaction to something, taking a dose of Benadryl (diphenhydramine) may help without a huge increased risk in intolerable side effects.
How Long To Separate
Even though Benadryl and NyQuil generally shouldn't be used together, they can certainly be taken the same day since both have a short duration of action.
Both Benadryl and NyQuil only last four to six hours per dose. Therefore, as long as they are separated by at least that amount of time, they shouldn't interact with one another.
Final Words
Thanks again for your question and please feel free to reach back out again!
References & sources
Glossary — Terms in This Answer
- Antihistamine
- A medication that blocks histamine, a chemical in the body that causes allergy symptoms like sneezing, itching, and runny nose.
- Diphenhydramine
- The active ingredient in Benadryl, a sedating antihistamine used to treat allergies and insomnia.
- Doxylamine
- A sedating antihistamine that is the active allergy-fighting ingredient in NyQuil.
- First-generation antihistamine
- An older class of antihistamines that commonly cause drowsiness as a side effect.
- Duplicate therapy
- Taking two medications that work the same way and have the same effect, which is generally unnecessary and increases risk of side effects.
- Histamine-1 receptor
- A protein in the body that histamine attaches to and activates to cause allergy symptoms.
- CNS depressant
- A substance that slows down brain and nervous system activity, causing drowsiness and reduced alertness.
- Adverse effects
- Unwanted or harmful side effects that a medication can cause.
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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