Cough Suppressants and MAOIs: What You Need to Know About Dextromethorphan Risks

Many people reach for over-the-counter cough syrup when they have a cold. It’s quick, easy, and usually safe-unless you’re taking an MAOI. If you’re on one of these antidepressants, that little bottle of cough medicine could be dangerous. Dextromethorphan, the main ingredient in Robitussin, Delsym, and dozens of other cold remedies, can trigger a life-threatening reaction when mixed with MAOIs like Nardil, Parnate, or selegiline. This isn’t a theoretical risk. It’s happened. And it can kill.

What Happens When Dextromethorphan Meets MAOIs?

Dextromethorphan works by calming the cough reflex in your brain. But it also has a side effect: it blocks serotonin reuptake. That means it makes more serotonin stick around in your brain. MAOIs do the same thing-except even more powerfully. They stop your body from breaking down serotonin at all. When you combine them, serotonin builds up fast. Too fast.

This isn’t just a mild side effect. It’s serotonin syndrome. Symptoms can show up within hours: high fever, muscle stiffness, confusion, rapid heartbeat, shaking, sweating, or even seizures. In severe cases, your body temperature can spike past 104°F. Your muscles lock up. Your organs start to fail. About 2% to 12% of people with severe serotonin syndrome don’t survive, even with hospital care.

The U.S. Food and Drug Administration first warned about this back in 1976. Yet, decades later, people are still getting hurt. Why? Because most don’t know. A 2019 survey found that 78% of people taking MAOIs didn’t realize common cough medicines contained dextromethorphan. That’s not ignorance-it’s a system failure.

The Science Behind the Danger

Dextromethorphan is broken down in your liver by an enzyme called CYP2D6. MAOIs don’t just affect serotonin-they also slow down this enzyme. That means dextromethorphan doesn’t get cleared from your body like it should. Studies show blood levels of dextromethorphan can jump 300% to 400% when taken with an MAOI. You’re not just getting the intended dose. You’re getting three to four times more.

And it’s not just the MAOI. If you’re also taking another drug that blocks CYP2D6-like fluoxetine, paroxetine, or even some heart medications-the risk gets even worse. That’s why some patients end up in the ER after taking just one or two doses of cough syrup. They weren’t trying to overdose. They just didn’t know what was in the bottle.

One patient on PatientsLikeMe described it this way: “I took my nighttime cold medicine while on Parnate. Four hours later, I couldn’t speak. My body was shaking. The ER doctors said I was lucky to be alive.” That story isn’t rare. Between 2010 and 2022, the FDA recorded 237 cases of serotonin syndrome linked to dextromethorphan and MAOIs. Nearly half of those patients needed hospitalization.

Who’s at Risk?

MAOIs are not the first-line antidepressant anymore. But they’re not rare, either. Around 1.2 million Americans use them each year. They’re often prescribed for treatment-resistant depression, anxiety disorders, or even Parkinson’s disease. People on these drugs are usually careful about diet-no aged cheese, no red wine. But they’re not thinking about cough medicine.

And it’s not just adults. Teens sometimes misuse dextromethorphan for its hallucinogenic effects. Parents might not realize their child is on an MAOI for depression or OCD. A teenager taking cough syrup for a cold could be in serious danger without anyone knowing why.

Even newer MAOIs aren’t always safe. While reversible ones like moclobemide carry lower risk, traditional irreversible MAOIs-still widely used-remain deadly when mixed with dextromethorphan. The European Medicines Agency now requires that every MAOI prescription come with a printed list of dangerous OTC drugs, including brand names like Delsym and Coricidin HBP Cough & Cold.

What Should You Do?

If you’re on an MAOI, here’s what you need to do:

1. Never take any cough medicine unless your doctor or pharmacist says it’s safe. Don’t assume “natural” or “non-drowsy” means safe.
2. Check the label. Look for “dextromethorphan” or “DM.” It’s in more than 120 products. Some are labeled as “cough suppressant,” others as “multi-symptom relief.”
3. Wait at least two weeks. If you’ve stopped your MAOI, wait 14 days before using dextromethorphan. The drug stays active in your system longer than you think.
4. Ask your pharmacist. A 2021 study showed pharmacist counseling reduced accidental interactions by 67%. That’s not a small number. It’s life-saving.

And if you’re a caregiver or family member of someone on an MAOI? Don’t assume they know. Help them check labels. Keep a list of safe alternatives handy.

Safe Alternatives for Cough Relief

You don’t need dextromethorphan to calm a cough. Here’s what works:

• Guaifenesin (Mucinex): This thins mucus. It doesn’t suppress coughing, but it helps your body clear the airway naturally. Just make sure it doesn’t have dextromethorphan added.
• Honey: A teaspoon of honey before bed is as effective as dextromethorphan for nighttime coughs, according to multiple studies. But be careful-some honey products contain tyramine, which can also interact with MAOIs. Stick to plain, unflavored honey.
• Steam and hydration: Warm tea, humidifiers, and drinking water help soothe irritated throats and loosen phlegm.
• Saline nasal sprays: If your cough comes from postnasal drip, clearing your nose can make a big difference.

And if you’re feeling sick? Don’t just reach for the nearest bottle. Call your doctor. Talk to your pharmacist. It’s better to be safe than sorry.

Why This Keeps Happening

The problem isn’t just patient ignorance. It’s labeling. A 2021 review found that only 38% of dextromethorphan products display the MAOI warning in a clear, noticeable way. Many labels bury the warning in tiny print on the back. Others don’t mention it at all.

The FDA proposed stronger labeling rules in 2022. The changes are expected to roll out by late 2024. But until then, you can’t rely on the bottle to protect you.

And there’s another gap: education. Only 43% of patients starting MAOI therapy get proper counseling about OTC risks. That’s not enough. If you’re prescribed an MAOI, you should walk out with a printed list of dangerous drugs-not just a prescription slip.

What to Do If You Think You’re Having a Reaction

If you or someone you know takes dextromethorphan and an MAOI and develops:

• Fever above 101°F
• Shaking or muscle rigidity
• Confusion, agitation, or hallucinations
• Rapid heartbeat or high blood pressure

-go to the ER immediately. Tell them you took cough medicine and an MAOI. Don’t wait. Don’t hope it’ll pass. Serotonin syndrome can kill faster than you think. Some patients die before the drugs leave their system.

There’s no antidote. Treatment is supportive: cooling the body, stopping the drugs, and managing symptoms. But early action saves lives.

Final Warning

Dextromethorphan is not a harmless cough suppressant. It’s a drug with serious risks-especially when combined with MAOIs. That’s why the American Psychiatric Association explicitly lists it among medications to avoid in MAOI users. This isn’t a footnote. It’s a red flag.

If you’re on an MAOI, treat every OTC cough medicine like a loaded gun. Read the label. Ask your pharmacist. Wait two weeks after stopping the MAOI. And if you’re unsure-don’t take it. Your life isn’t worth the risk.