Taking melatonin with NyQuil is best avoided unless a doctor or pharmacist tells you it is appropriate. One 30 mL dose of regular liquid NyQuil contains 12.5 mg of doxylamine, a sedating antihistamine. Combining it with melatonin can increase sleepiness, dizziness, poor coordination, confusion and, in some people, excessive slowing of the nervous system or breathing.
Melatonin and NyQuil: At a Glance
| Question | Practical answer |
|---|---|
| Can you take them together? | Avoid combining them without advice from a doctor or pharmacist. |
| What is the main concern? | Extra sedation and reduced alertness. |
| Does taking them hours apart guarantee safety? | No. Their effects may overlap later the same night. |
| Can you drink alcohol with them? | No. Alcohol can increase sleepiness and impairment. |
| Should you drive afterward? | No, especially if you feel sleepy, dizzy or slowed down. |
| What if you already took both? | Do not take more sedating medicine or alcohol. Watch for excessive sleepiness and seek advice if you are concerned. |
Why Can Melatonin and NyQuil Cause Problems Together?
Melatonin and some NyQuil ingredients can both make you sleepy, so their effects may add up.
Regular NyQuil Cold & Flu commonly contains:
- Doxylamine succinate, a sedating antihistamine
- Dextromethorphan, a cough suppressant
- Acetaminophen, a pain and fever reducer
The standard liquid formulation contains 12.5 mg of doxylamine and 30 mg of dextromethorphan in each 30 mL dose. The NyQuil label warns that marked drowsiness can occur and that sedatives or tranquilizers may make this worse.
Melatonin can add to the sleepiness caused by doxylamine and dextromethorphan. Drug interaction guidance also warns about increased central nervous system and breathing depression, along with reduced attention, judgment and coordination.
Which NyQuil Product Are You Taking?
NyQuil products contain different ingredients, so check the Drug Facts panel on the exact bottle or package before combining one with melatonin.
NyQuil Severe Cold & Flu adds phenylephrine, a nasal decongestant. Its listed active ingredients include acetaminophen, dextromethorphan, doxylamine and phenylephrine. It also contains a different amount of dextromethorphan from regular NyQuil.
For the melatonin interaction, the ingredient to pay closest attention to is usually doxylamine, which is listed as an antihistamine.
What Should You Do If You Already Took Both?
If you took normal doses and feel well:
- Do not take more melatonin or NyQuil, drink alcohol, or use another medicine that makes you sleepy.
- Do not drive or operate machinery.
- Stay somewhere safe and watch for unusual or worsening drowsiness.
- Contact a pharmacist or Poison Control if you took more than directed, are unsure how much you took, or use other medicines.
In the United States, Poison Control is available 24 hours a day at 1-800-222-1222.
Call 911 for trouble breathing, slow or shallow breathing, fainting, a seizure, blue lips, severe confusion or if the person cannot be awakened.
Important Safety Issue: Acetaminophen
Acetaminophen is a separate risk. Melatonin does not contain acetaminophen, but many NyQuil products do. Do not combine NyQuil with Tylenol or another acetaminophen-containing medicine unless a healthcare professional has confirmed that the total amount is safe. Too much acetaminophen can cause severe liver damage.
Ask a healthcare professional before using NyQuil or melatonin if you:
- Are older, frail or prone to falls
- Have sleep apnea, asthma or another breathing problem
- Have liver disease
- Take opioids, sleep medicines, tranquilizers, sedating antihistamines or other medicines that cause drowsiness
- Are pregnant or breastfeeding
- Are giving either medicine to a child
Bottom line: Check the exact NyQuil product and ask a pharmacist before taking it with melatonin.