Both Dayquil and Nyquil are flu medications that contain similar active ingredients — namely, paracetamol (also known as acetaminophen), the same drug found in Tylenol, and diphenhydramine, better known as the antihistamine found in Benadryl.

Both drugs contain different amounts of these two active ingredients; however, it is possible to take both at the same time. When taking both of these medicines simultaneously, you should be aware of any potential interactions or side effects

When Can You Take Dayquil and Nyquil Together?

You can take both Dayquil and Nyquil together as long as you do so with care. Be cautious if you have allergies to either of these medications, or if you have certain other health conditions such as liver or kidney disease. Additionally, pregnant women should be especially careful when taking these drugs, as they are both known to be harmful to unborn children

. You should also take care when taking Dayquil and Nyquil together if you have a history of drug or alcohol abuse, as these medications can be addictive and increase the risk of overdose. If you are taking any other medications, it is important to be aware of any possible interactions.

Keep in mind that there is no benefit to taking a higher dose of Dayquil and Nyquil than is necessary to alleviate your symptoms. Doing so is likely to increase the risk of side effects.

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Why You Shouldn’t Mix Dayquil and Nyquil

It is not recommended that you mix Dayquil and Nyquil for several reasons. First, both Dayquil and Nyquil have been shown to have similar potential for cough suppression, but Nyquil is 50% more potent. This means that a higher dose of Nyquil will be necessary to achieve the same effect as a smaller dose of Dayquil.

Therefore, taking both drugs together is likely to lead to an overdose. Additionally, you should be careful when mixing Dayquil and Nyquil because the diphenhydramine found in both drugs is metabolized by the same liver enzyme. Therefore, the combination of both drugs is likely to increase the rate of metabolism.

This means that both drugs will have a shorter duration of action, and you may need to take higher doses to achieve the same results. Taking too much of either drug can lead to serious side effects.

Mixing Dayquil and Benadryl

You should avoid mixing Dayquil and Benadryl because both drugs are metabolized by the cytochrome P450 pathway in the liver. As such, taking the two drugs together is likely to lead to an increased rate of metabolism that results in a shorter duration of action. This can lead to an increased risk of overdose.

Additionally, because all drugs metabolized by the cytochrome P450 pathway have the potential to inhibit or induce the enzymes in this pathway, mixing Dayquil and Benadryl may change the metabolism of either or both drugs. This can also lead to an increased risk of overdose.

Mixing Nyquil and Benadryl

Given that both Dayquil and Nyquil are metabolized by cytochrome P450 and Benadryl is metabolized by the P450 2C9 enzyme, taking the three drugs together is likely to lead to an increased rate of metabolism. As with the combination of Dayquil and Benadryl, this can lead to an increased risk of overdose.

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Additionally, as with the combination of Dayquil and Benadryl, the metabolism of one or both of these drugs may be altered by the presence of the other drugs in the system. This can also lead to an increased risk of overdose.

How to Take Dayquil and Nyquil Together


If you are taking both Dayquil and Nyquil, it is important to consider the dosage. Because both drugs are available in different quantities, it is recommended that you take the smallest dose of each drug necessary to alleviate your symptoms. When taking both drugs together, you should keep in mind that the diphenhydramine in both Dayquil and Nyquil is metabolized by the same liver enzyme.

Therefore, it is likely that the rate of metabolism will increase if you take both drugs at the same time. This may lead to a shorter duration of action for both drugs and may require you to take a higher dose than you would normally.

Final Words

In most cases, taking two cold medications at the same time is fine. However, you should be careful to avoid mixing the two types of medications if you can. Taking Dayquil and Nyquil together is fine as long as you take the recommended dose of each drug.


David Warren
Author

David Warren is a pharmaceutical specialist that dispenses prescription medication on a daily basis. He received a Bachelor of Science degree in pharmacy from the University of Tennessee in 1991. With over 50 publications on medication-related and pharmacy topics, David has been able to share his experiences and knowledge with others. David with lots of experience and knowledge in medications that are utilized to treat a wide range of medical conditions. Before David dispenses a medication to a patient, he will go over the side effects, dosage recommendation and contraindications.