What medications cannot be taken with Delsym? A guide to dangerous drug interactions

October 9, 2025 •

3 min read

Dextromethorphan (DXM), the active ingredient in Delsym, is a common cough suppressant found in over-the-counter cold remedies. However, combining Delsym with certain other drugs can lead to dangerous and potentially fatal interactions, making it crucial to understand what medications cannot be taken with Delsym.

Quick Summary

A guide to dangerous drug interactions involving Delsym (dextromethorphan), with a focus on why it should never be combined with MAOIs due to the risk of life-threatening serotonin syndrome. Interactions with alcohol, SSRIs, and other substances also pose serious risks.

Key Points

Avoid MAOIs: Never combine Delsym with Monoamine Oxidase Inhibitors (MAOIs) due to the risk of life-threatening serotonin syndrome; wait at least 14 days after stopping an MAOI before use.
Steer Clear of Alcohol: Avoid drinking alcohol with Delsym, as it significantly increases the risk of side effects like severe drowsiness, dizziness, and impaired coordination.
Caution with Antidepressants: Be cautious when combining Delsym with Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs) due to the risk of serotonin syndrome.
Read All Labels: Check all over-the-counter medications for dextromethorphan to prevent accidental overdose from combining multiple cough and cold products.
Consult a Professional: Always talk to a doctor or pharmacist about your complete medication list, including supplements like St. John's wort, to identify potential interactions.
Be Mindful of Grapefruit Juice: Limit or avoid grapefruit juice, as it can increase dextromethorphan levels in the body and heighten the risk of side effects.

Critical Dangers: MAOIs and Serotonin Syndrome

The most serious and potentially fatal interaction involving Delsym is with a class of antidepressants known as Monoamine Oxidase Inhibitors (MAOIs). MAOIs are prescribed for conditions like depression, anxiety, and Parkinson's disease. The combination of dextromethorphan and an MAOI can cause a life-threatening condition called serotonin syndrome.

How Serotonin Syndrome Occurs

Serotonin syndrome is caused by excessive levels of serotonin, a neurotransmitter, in the central nervous system. Both Delsym (dextromethorphan) and MAOIs affect serotonin levels, and their combined effect can lead to an overload. Symptoms of serotonin syndrome can include:

Agitation or restlessness
Confusion or hallucinations
Rapid heart rate and high blood pressure
Excessive sweating and fever
Muscle rigidity or tremors
Severe cases can lead to seizures, coma, and death

The 14-Day Rule

Because of the severity of this interaction, you must not take Delsym if you have taken an MAOI in the past 14 days. This allows enough time for the MAOI to clear from your body and prevent a dangerous reaction. It is essential to talk to your healthcare provider or pharmacist if you are unsure whether your medication is an MAOI.

Other Serotonergic Medications

Beyond MAOIs, other medications that also affect serotonin levels can increase the risk of serotonin syndrome when combined with Delsym. It is crucial to be cautious if you are taking these drugs, and to always consult a doctor before mixing them.

Common examples include:

Selective Serotonin Reuptake Inhibitors (SSRIs): Such as fluoxetine (Prozac), sertraline (Zoloft), and paroxetine (Paxil).
Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs): Such as venlafaxine (Effexor XR) and duloxetine (Cymbalta).
Tricyclic Antidepressants (TCAs): Such as amitriptyline.
Certain Pain Medications: Including tramadol.
Herbal Supplements: St. John's wort is also known to increase serotonin and should be avoided.

Central Nervous System (CNS) Depressants

Both dextromethorphan and alcohol are central nervous system depressants. When combined, their effects are amplified, leading to enhanced drowsiness, dizziness, and impaired judgment. This can significantly increase the risk of accidents and overdose.

Other CNS depressants to avoid include:

Alcohol: Avoid alcoholic beverages entirely while taking Delsym.
Opioids and Sedatives: Medications like opioids, muscle relaxers, and benzodiazepines can increase sedation and the risk of respiratory depression.

Potential Food and Drug Interactions

Several other substances and conditions require caution with Delsym. Always read the label and consult a healthcare professional before combining medications.

Key interactions to be aware of include:

Grapefruit and Grapefruit Juice: Can inhibit enzymes that metabolize dextromethorphan, leading to higher drug levels and an increased risk of side effects like dizziness and restlessness.
Other Cough and Cold Medications: Many OTC products contain dextromethorphan or other similar ingredients. Combining multiple products can lead to an overdose. Always check the active ingredients list.
CYP2D6 Inhibitors: Medications that inhibit this enzyme, such as quinidine, can increase dextromethorphan levels in the body.

Comparison of Major Delsym Interactions


Interaction Type	Primary Risk	Symptoms	Safety Precaution	Outcome if Ignored
MAOIs	Serotonin Syndrome	Confusion, agitation, rapid heart rate, fever, seizures, coma	Do not take within 14 days of an MAOI.	Potentially fatal.
Alcohol	Enhanced CNS Depression	Severe drowsiness, dizziness, impaired coordination and judgment	Avoid alcohol entirely.	Increased risk of accidents, overdose, and respiratory depression.
SSRIs/SNRIs	Serotonin Syndrome	Similar to MAOI interaction, but often less severe	Consult doctor, may require dose adjustment or monitoring.	Risk of life-threatening serotonin syndrome.
Grapefruit Juice	Increased Drug Levels	Restlessness, dizziness, nausea, vomiting.	Limit or avoid intake.	Increased risk of side effects and toxicity.

Conclusion: Prioritizing Safety with Delsym

While Delsym is an effective over-the-counter cough suppressant for many, its active ingredient, dextromethorphan, carries significant risks when combined with certain other substances. The most dangerous interaction is with MAOIs, which can lead to fatal serotonin syndrome. Interactions with alcohol, SSRIs, and other CNS depressants also pose serious threats and should be taken with extreme caution. To ensure your safety, always read the product label, inform your healthcare provider of all medications and supplements you are taking, and never exceed the recommended dosage. When in doubt, it is always best to consult a pharmacist or doctor before taking a new medication.

For more detailed information on drug interactions, consult a reliable resource like Drugs.com.

Disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice. Always consult with a healthcare professional regarding any medical concerns or before starting or stopping any medication.

Frequently Asked Questions

You should not take Delsym if you are on an MAOI antidepressant or have taken one within the last 14 days. If you are on other types of antidepressants, such as SSRIs or SNRIs, consult your doctor or pharmacist first, as combining them can increase the risk of serotonin syndrome.

Serotonin syndrome is a potentially life-threatening condition caused by too much serotonin in the body. Symptoms include confusion, agitation, rapid heart rate, high blood pressure, and tremors. It can occur when medications like Delsym and MAOIs, which both affect serotonin, are combined.

No, it is not safe to drink alcohol while taking Delsym. Both are central nervous system depressants, and combining them can lead to increased dizziness, drowsiness, impaired coordination, and a heightened risk of overdose and respiratory depression.

You should always check the active ingredients of any other cold or cough medicine you plan to take. Many contain dextromethorphan (the same active ingredient as Delsym), and combining them can lead to an overdose.

Grapefruit juice can interfere with the metabolism of dextromethorphan, causing higher levels of the drug to build up in your system. This can increase the risk of side effects such as dizziness and nausea.

Yes, the herbal supplement St. John's wort should be avoided while taking Delsym. Like some antidepressants, it can affect serotonin levels and increase the risk of serotonin syndrome.

If you experience symptoms like severe dizziness, anxiety, confusion, hallucinations, or breathing problems after taking Delsym, stop using it immediately and seek emergency medical attention or call a poison control center.