Doxycycline and nyquil are two medicines used to treat different types of bacterial infections. Taking these medications together can have negative consequences, and it is best to avoid taking them at the same time.

Read on to learn more about whether you can take nyquil with doxycycline and what the risks are if you take them at the same time. If you have further questions about the interaction of doxycycline and nyquil, speak to your doctor or pharmacist.

What is nyquil?

Nyquil is a cough syrup, and it contains dextromethorphan (DM). DM is a cough suppressant, and is also used to treat colds, flu and allergies. DM works by blocking a chemical that is released during an allergic reaction, thereby reducing inflammation and irritation in the airways.

Nyquil is also used for pain, muscle spasms, anxiety, and to treat insomnia. DM is not a muscle relaxant. It does not work by relaxing the muscles, but by increasing your general feeling of calmness by blocking the release of certain chemicals.

What is doxycycline?

Doxycycline is an antibiotic that is used to treat bacterial infections in the lungs and respiratory system, urinary tract, skin, and genitals. Doxycycline is used to treat bacterial infections such as pneumonia, anthrax, Lyme disease, chlamydia, and gonorrhea. It may also be used to prevent or slow the spread of anthrax infection.

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What happens when you take nyquil with doxycycline?

Taking nyquil with doxycycline can increase the amount of doxycycline in your blood. Increased blood levels of doxycycline can lead to more side effects, such as nausea and vomiting. If you take nyquil with doxycycline, you should have your blood tested more frequently for potential drug interactions.

This is because doxycycline is metabolized in the liver, and nyquil may increase the rate at which the drug is broken down. This could lead to lower blood levels of doxycycline and potentially cause a relapse of your bacterial infection.

Is it safe to take nyquil and doxy together?

Taking nyquil with doxycycline may result in unwanted side effects, such as an increase in the amount of doxycycline in your blood. Because of this, it is best to avoid taking nyquil and doxycycline together. However, if you are taking doxycycline for anthrax, you should not take nyquil at the same time.

The combination of these two medications can trigger a potentially fatal reaction called the “chemical warfare agent” syndrome. This syndrome occurs when anthrax spores in your body react to the combination of medications and cause severe damage to your organs.

Doxycycline and birth control

Doxycycline is often prescribed as a method of birth control. This method is not reliable because doxycycline breaks down in the body and is excreted in the urine. Therefore, your body can quickly rid itself of the drug, preventing it from having any effect on pregnancy.

Doxycycline may cause your period to come earlier than expected. The drug may also make your period heavier or last longer than usual. Doxycycline should not be used as birth control if you are taking it for anthrax or if you have a bacterial infection.

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Doxycycline and St. John’s wort

St. John’s wort is a herbal remedy that is used to treat depression. The drug interacts with doxycycline and can reduce its effect. If you suffer from depression and take doxycycline to treat it, you should avoid taking St. John’s wort at the same time.

Doxycycline and St. John’s wort should not be taken together because St. John’s wort can reduce the effectiveness of doxycycline. This can leave you more susceptible to infection, especially if you are taking doxycycline for a bacterial infection.

Final words

If you suffer from allergies and take doxycycline for this reason, you can continue to take it with nyquil. However, you should avoid taking nyquil and doxycycline together because they can have a negative effect on each other. If you suffer from a bacterial infection and take doxycycline, you should avoid taking nyquil at the same time.

Taking nyquil with doxycycline can cause unwanted side effects. When taking a drug, it’s important to be aware of potential side effects and interactions with other medications. Doxycycline and nyquil are two of the most commonly prescribed medications, and can be taken together without causing any negative interactions.


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.