Dextromethorphan belongs to a group of medications called antitussives (cough suppressants). This medication works by suppressing dry, hacking coughs. It is usually used for a short term to control coughing associated with the flu, a cold, or due to inhaled irritants.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or pharmacist or are not sure why you are taking this medication, speak to your doctor or pharmacist. Do not stop taking this medication without consulting your doctor.

For adults, the recommended dose of dextromethorphan is 10 mg to 20 mg taken by mouth every 4 hours, or 30 mg taken by mouth every 6 to 8 hours. The maximum daily dose for adults is 120 mg.

For children 6 to 11 years of age, the recommended dose is 5 mg to 10 mg taken by mouth every 4 hours. The maximum daily dose for children is 60 mg.

This medication is not recommended for children under the age of 6 years.

Dextromethorphan may be taken with food or on an empty stomach.

There may be different strengths of dextromethorphan products available. Make sure you read the label and ask your doctor or pharmacist how much and how often you should take it. It is important that this medication be taken exactly as recommended by your doctor or pharmacist, or as indicated on the product label.

Use an oral syringe to measure each dose of the liquid, as it gives a more accurate measurement than household teaspoons.

This medication is often taken on an "as needed" basis, however if your doctor has suggested you take dextromethorphan regularly and you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Ask your doctor or pharmacist for details.

Do not take dextromethorphan if you:

• are allergic to dextromethorphan or any ingredients of the medication
• are taking MAO inhibitors (e.g., moclobemide, rasagiline, selegiline, tranylcypromine) or have taken them in the previous 2 weeks
• have respiratory depression (breathing rate below normal)

Do not give this medication to children less than 6 years old.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• confusion
• constipation
• dizziness
• drowsiness
• nausea
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• blurred vision
• excitement
• irritability
• nervousness

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of an allergic reaction (hives; difficulty breathing; swelling of the face, tongue, or throat)
• slowed or decreased breathing

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Accidental overdose: If you take more than the recommended amount of dextromethorphan, contact your doctor or a local poison control centre immediately.

Medical conditions: Talk to your doctor or pharmacist about using this product if you have serious kidney or liver disease, high blood pressure, heart or thyroid disease, diabetes, asthma, chronic lung disease or shortness of breath, persistent or chronic cough, glaucoma, difficulty urinating due to enlargement of prostate gland, chronic alcoholism, or any other medical condition or are taking medications for depression.

Persistent symptoms: If your cough gets worse, lasts more than 7 days, or tends to recur, or if you are coughing up phlegm or mucus or have a fever for more than 3 days, talk to your doctor.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you are pregnant, talk to your doctor or pharmacist before taking this medication.

Breast-feeding: It is not known if dextromethorphan passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: This medication should not be used by children under 6 years of age.

Seniors: If you are a senior, talk to your doctor or pharmacist before taking this medication.

There may be an interaction between dextromethorphan and any of the following:

• abiraterone acetate
• bupropion
• cinacalcet
• dacomitinib
• darunavir
• darifenacin
• fentanyl
• lithium
• memantine
• meperidine
• mirabegron
• mirtazapine
• monoamine oxidase inhibitors (MAOIs; e.g., safinamide, selegiline, tranylcypromine)
• peginterferon alfa-2b
• St. John's wort
• selective serotonin reuptake inhibitors (e.g., citalopram, fluoxetine, paroxetine, vortioxetine)
• serotonin/norepinephrine reuptake inhibitors (SNRIs; e.g., desvenlafaxine, duloxetine, venlafaxine)
• terbinafine
• tipranavir
• tramadol
• trazodone
• tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, imipramine)
• tryptophan
• vilazodone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.