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07/25/2024 | Press release | Distributed by Public on 07/25/2024 14:58

6 Dextromethorphan Side Effects You Should Know About

Key takeaways:

  • Dextromethorphan (Delsym, Robitussin) is a cough suppressant. It's usually well-tolerated. But it can cause mild side effects like nausea, dizziness, and drowsiness.

  • More serious dextromethorphan side effects include serotonin syndrome. Dextromethorphan also carries serious risks of misuse and overdose. Taking it as recommended can help minimize these risks.

  • Adults shouldn't take more than 120 mg per day of dextromethorphan. And don't take it for longer than 7 days. If your cough doesn't improve by then, talk to a healthcare professional about what to try next.

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Dextromethorphan (Delsym, Robitussin) is a cough suppressant. It works by controlling your cough reflex so that you cough less. And it's used pretty frequently, with over 100 different over-the-counter (OTC) products containing dextromethorphan. For example, it's part of Mucinex DM (guaifenesin / dextromethorphan) and with Dayquil Cold and Flu (acetaminophen / dextromethorphan / phenylephrine).

If you use a product that contains dextromethorphan (which is often indicated with the letters "DM"), knowing about its risks can help keep you safe. Though dextromethorphan side effects are usually mild, some risks are more serious.

Dextromethorphan side effects at a glance

While it's uncommon to experience dextromethorphan side effects, it's possible. But if they occur, they're usually mild.

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Mild dextromethorphan side effects include:

  • Nausea

  • Stomach discomfort

  • Dizziness

  • Drowsiness

Rare but serious dextromethorphan risks include:

  • Serotonin syndrome

  • Misuse

If dextromethorphan is misused - such as taking higher than recommended doses - overdose can occur. Symptoms may include slowed breathing, a fast heart rate, and hallucinations. In the most severe cases, coma and death may occur.

Let's take an in-depth look at six dextromethorphan side effects and what to do if you experience them.

.1. Gastrointestinal problems

Although it's not common, dextromethorphan can sometimes cause mild gastrointestinal (GI) issues, like nausea and stomach pain. Since dextromethorphan is usually taken throughout the day, it might help to take your doses with food. This may help relieve nausea.

If you experience serious GI effects - like vomiting - it may be a sign that you've taken too much dextromethorphan. The maximum safe dose of dextromethorphan for adults is 120 mg per day. If you're taking other cough and cold medications (or the prescription antidepressant Auvelity, which contains dextromethorphan and bupropion), check whether these medications also contain dextromethorphan. Your total daily dose from all sources shouldn't exceed 120 mg.

2. Dizziness

Rarely, dextromethorphan may cause dizziness at recommended doses. But it's much more likely to happen with doses that are too high.

If you're starting dextromethorphan, use caution when completing tasks that require alertness - such as driving - until you see if dextromethorphan makes you dizzy. And take your time when moving from a lying or sitting position to standing. This will help you avoid falls and potentially serious injury, especially for older adults.

It's also a good idea to avoid alcohol. Drinking alcohol, especially too much of it, can make dizziness worse. Medications such as opioids and benzodiazepines can also worsen dizziness and are best avoided with dextromethorphan.

If your dizziness with dextromethorphan is severe, reach out to your healthcare professional (HCP). They may recommend only taking dextromethorphan at night or avoiding it altogether.

3. Drowsiness

Like dizziness, drowsiness is a rare dextromethorphan side effect. But it can happen.

If you experience drowsiness, you can try only taking your dose at night. But if one dose a day doesn't help your cough symptoms, this may not be the best option.

As with dizziness, it's a good idea to avoid using other medications that can worsen drowsiness. This includes some OTC antihistamines like diphenhydramine (Benadryl, ZzzQuil) and doxylamine (Unisom SleepTabs). It also includes several prescription medications, like some antidepressants, opioids, and benzodiazepines. Talk to a HCP about whether any of your medications can worsen drowsiness, and whether you need to make any changes to your medication regimen.

4. Serotonin syndrome

Serotonin syndrome is a rare but potentially life-threatening condition. It happens when there's too much serotonin in the brain. Serotonin is a chemical that helps regulate many body functions, including your mood.

If you're only taking dextromethorphan, it's highly unlikely you'll experience serotonin syndrome. But if you take dextromethorphan with other medications that increase serotonin, the risk is higher. Examples of medications that increase serotonin include:

  • Selective serotonin reuptake inhibitors (SSRIs) like fluoxetine (Prozac) and escitalopram (Lexapro)

  • Serotonin norepinephrine reuptake inhibitors (SNRIs) like duloxetine (Cymbalta) and venlafaxine

  • Monoamine oxidase inhibitors (MAOIs) like selegiline (Zelapar, Emsam) and rasagiline (Azilect)

  • Pain medications like tramadol (Qdolo, ConZip)

  • Triptans like sumatriptan (Imitrex)

  • Antibiotics like linezolid (Zyvox)

Tell your pharmacist about all the prescription and OTC medications you take. They can check if you take other medications that increase serotonin. In some cases, combining dextromethorphan with another medication that increases serotonin should be completely avoided. For example, MAOIs and dextromethorphan shouldn't be combined, and may need to be avoided within 2 weeks of each other. But other combinations may be considered safe if you're able to monitor for symptoms of serotonin syndrome.

Symptoms may include a fast heart rate, increased sweating, and fever. If you experience agitation, confusion, or trouble controlling your movements, seek emergency care. These may be potentially serious signs of serotonin syndrome.

5. Misuse

Taking large amounts of dextromethorphan can create a "high" feeling. This is sometimes referred to as "robo-tripping" or "skittling." For some people, it may feel like drinking alcohol or taking marijuana. But it can also cause hallucinations or panic. More seriously, it can cause seizures, brain damage, and heart problems. And in some cases, it can lead to coma and death.

It's possible to get addicted to dextromethorphan. It may feel similar to other substance use disorders. A person may feel preoccupied with getting dextromethorphan, use larger amounts than what is recommended, and be unable to cut back on their use.

Teens are particularly vulnerable to dextromethorphan misuse. In many states, you have to be 18 years old to buy dextromethorphan. This rule, along with efforts to educate parents and teens about dextromethorphan, has lowered dextromethorphan misuse in recent years.

If you or someone you know struggles with substance use, help is available. Call SAMHSA's National Helpline at 1-800-662-4357 to learn about resources in your area.

6. Accidental dextromethorphan overdose

Taking too much dextromethorphan can lead to an overdose. Signs of dextromethorphan overdose include:

  • Slow breathing

  • Fast heart rate

  • Psychosis (a changed perception of reality)

  • Seizures

  • High blood pressure

  • Coma

  • Death

To avoid a dextromethorphan overdose, make sure you know exactly how much dextromethorphan you're taking. Adults shouldn't take more than 120 mg per day for a maximum of 7 days. If your cough doesn't improve by then, talk to an HCP. And avoid taking other medications or substances that can cause drowsiness, such as opioids, benzodiazepines, and alcohol.

Remember that dextromethorphan is a common ingredient in combination OTC cough and cold products. It's also one of two active ingredients in the prescription medication Auvelity. It's easy to accidentally take too much dextromethorphan if you're using a few different products that contain it. If you need help calculating how much dextromethorphan you're taking, talk to your pharmacist. They can help make sure you're not taking too much.

Frequently asked questions

1. Who should avoid dextromethorphan?
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You may need to avoid dextromethorphan if you're taking medications that increase serotonin levels, like MAOIs or SSRIs. You may also need to avoid it if you're already taking a medication that has dextromethorphan in it, like Auvelity.

It's also best to check with an HCP before taking dextromethorphan if you're pregnant or breastfeeding, though it's generally considered safe.

2. Is there an age restriction for taking dextromethorphan?
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It depends on what product we're talking about. For example, the manufacturers of liquid dextromethorphan state that adults and children older than 4 years old can use this product. But dextromethorphan caplets should be avoided in people under 12 years old.

What's more, dextromethorphan may not be effective in children. In this case, the risks may outweigh the benefits. Talk to your child's pediatrician before giving them cough medication like dextromethorphan.

3. Can dextromethorphan cause anxiety?
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Dextromethorphan isn't known to cause anxiety at recommended doses. But if you take too much it can cause psychiatric side effects, including agitation and panic. If you're feeling anxious after taking dextromethorphan, it could be a sign that you've taken too much.

The bottom line

Dextromethorphan (Delsym, Robitussin) is a cough suppressant. It's usually well-tolerated but mild side effects may include nausea, drowsiness, and dizziness. More serious dextromethorphan side effects include serotonin syndrome. Dextromethorphan misuse is also possible, and this can lead to overdose.

The maximum safe dose of dextromethorphan is 120 mg per day for adults. Taking more than this increases your risk for misuse and overdose. Don't take dextromethorphan for more than 7 days at a time. If your cough doesn't improve by then, talk to a healthcare professional.

References

Consumer Healthcare Products Association. (2021). Teen abuse of cough and cold medicines is at a historic low after largest one-year decline in 2021.

Drug Enforcement Administration. (2020). Drug fact sheet: DXM.

View All References (6)
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Edinoff, A. N., et al. (2022). Clinically relevant drug interactions with monoamine oxidase inhibitors. Health Psychology Research.

Journey, J. D., et al. (2023). Dextromethorphan toxicity. StatPearls.

Lam, S. H. F., et al. (2021). Use of antitussive medications in acute cough in young children. Journal of the American College Emergency Physicians Open.

Moon, K. T. (2008). Honey, dextromethorphan, and no treatment in children with cough. American Family Physician.

National Capital Poison Center. (n.d.). Dextromethorphan abuse.

Oh, S. R., et al. (2022). Dextromethorphan. StatPearls.

GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.

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