Dextromethorphan is a generic, over-the-counter (OTC) drug that’s used to help relieve cough in adults and certain children. As with other drugs, dextromethorphan can cause side effects, such as drowsiness or dizziness.

Dextromethorphan is available as the brand-name drug Delsym.

Dextromethorphan comes as an oral liquid-filled capsule and an oral suspension.

Read on to learn about potential common, mild, and serious side effects of dextromethorphan. For a general overview of the drug, including details about its uses, see this article.

Dextromethorphan can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if they last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took dextromethorphan:

  • dizziness
  • vomiting
  • abdominal pain
  • drowsiness*
  • nausea*

* For more information about this side effect, see the “Dextromethorphan: Side effect specifics” section.

Mild side effects can occur with dextromethorphan use. This list doesn’t include all possible mild side effects of the drug. For more information, talk with your doctor or pharmacist.

Mild side effects that have been reported with dextromethorphan include:

  • restlessness
  • nervousness
  • dizziness
  • abdominal pain
  • vomiting
  • skin rash
  • drowsiness*
  • nausea*

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking dextromethorphan and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see the “Dextromethorphan: Side effect specifics” section.

In rare cases, dextromethorphan may cause serious side effects, including a severe allergic reaction. For more information, see the “Allergic reaction” section that follows.

If you develop serious side effects while taking dextromethorphan, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

ALLERGIC REACTION

For some people, dextromethorphan capsules or suspension can cause an allergic reaction.

In general, symptoms of allergic reaction can be mild or serious.

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to dextromethorphan, your doctor may recommend taking a different medication instead.

Dextromethorphan may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Is there a risk of misuse and dependence with dextromethorphan?

Yes. While dextromethorphan is not a controlled substance, there’s still a risk of misuse and dependence because of how the drug works in the brain. With misuse, a drug is taken in a way that’s not recommended. With dependence, your body becomes used to a drug and needs it to function as usual.

Taking too much dextromethorphan can cause a “high” feeling. Taking the drug in a way other than recommended can also lead to side effects and overdose, with symptoms that may include:

Do not take more dextromethorphan than recommended. Talk with your doctor or pharmacist if you have questions or concerns about the dosage of dextromethorphan that is safe for you.

How do side effects of dextromethorphan in children compare with side effects seen in adults?

The side effects in children are the same as those seen in adults. (For more information about side effects, see the “Mild side effects” section above.)

However, dextromethrophan may not be safe for children of all ages. Dextromethorphan oral suspension may be given to children ages 4 years and older and the oral softgels may be used in children ages 12 years and older.

Talk with your child’s doctor or pharmacist if you have questions about the side effects your child may experience while taking dextromethorphan.

Learn more about some of the side effects that dextromethorphan may cause. For more information about the side effects of dextromethorphan, talk with your doctor or pharmacist.

Drowsiness

Dextromethorphan can cause drowsiness, but this side effect isn’t common. If drowsiness does occur, it’s usually mild. Taking a higher dose of dextromethorphan may increase the risk of drowsiness.

What you can do

Avoid taking Dextromethorphan with other medications that may cause drowsiness during the day. Some over-the-counter medications that may cause drowsiness include antihistamines, such as diphenhydramine (Benadryl) or doxylamine (Unisom). Prescription medications, such as opioids, benzodiazepines, and some antidepressants, can also worsen drowsiness.

Drinking alcohol can cause drowsiness and should be avoided while taking dextromethorphan. Don’t drive, use machinery, or do anything that needs alertness until you know how your body reacts to dextromethorphan.

Talk with your doctor or pharmacist if you have drowsiness while taking dextromethorphan. They may suggest ways to help manage this side effect.

Nausea

Taking dextromethorphan can sometimes cause nausea, but it isn’t common. Typically, nausea experienced with dextromethorphan is mild.

What you can do

If you experience nausea throughout the day, taking your dose of dextromethorphan with food or milk may help ease that side effect.

Talk with your doctor or pharmacist if your symptoms are bothersome. They may recommend a different medication for your cough.

Below is important information you should consider before taking dextromethorphan.

Other precautions

Before taking dextromethorphan, discuss your health history with your doctor. Dextromethorphan may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.