Mucinex DM (Dextromethorphan And Guaifenesin) – Side Effects, Interactions, Uses, Dosage, Warnings

Dextromethorphan is a cough suppressant. Guaifenesin is an expectorant.

Dextromethorphan and guaifenesin is a combination medicine used to treat cough and chest congestion caused by the common cold or allergies.

Dextromethorphan will not treat a cough that is caused by smoking.

There are many brands and forms of this medication available and not all brands are listed on this leaflet.

Dextromethorphan and guaifenesin may also be used for purposes not listed in this medication guide.


What is Mucinex DM (Dextromethorphan And Guaifenesin) used for?

  • Cough


What is the most important information I should know about Mucinex DM (Dextromethorphan And Guaifenesin)?

Do not use this medicine if you have taken an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, and tranylcypromine.

Ask a doctor or pharmacist if this medicine is safe to use if you have:

  • a cough with mucus; or
  • asthma, emphysema, or chronic bronchitis.

Ask a doctor before using this medicine if you are pregnant or breast-feeding.

This medicine may contain phenylalanine. Check the medication label if you have phenylketonuria (PKU).

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Side Effects

What are the side effects of Mucinex DM (Dextromethorphan And Guaifenesin)?

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using this medicine and call your doctor at once if you have:

  • mood changes;
  • severe headache; or
  • severe dizziness or anxiety, feeling like you might pass out;.

Common side effects may include:

  • dizziness, drowsiness;
  • sleep problems (insomnia);
  • diarrhea; or
  • feeling nervous, restless, anxious, or irritable;.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Pregnancy & Breastfeeding

Can I take Mucinex DM (Dextromethorphan And Guaifenesin) if I’m pregnant or breastfeeding?

Ask a doctor before using this medicine if you are pregnant or breast-feeding.


What drugs and food should I avoid while taking Mucinex DM (Dextromethorphan And Guaifenesin)?

Avoid driving or hazardous activity until you know how this medicine will affect you. Your reactions could be impaired.

Drinking alcohol with this medicine can cause side effects.

Ask a doctor or pharmacist before using other cough or cold medicines that may contain similar ingredients.

Dosage Guidelines & Tips

How to take Mucinex DM (Dextromethorphan And Guaifenesin)?

Use Mucinex DM (Dextromethorphan And Guaifenesin) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Use exactly as directed on the label, or as prescribed by your doctor. Cold or cough medicine is only for short-term use until your symptoms clear up.

Always follow directions on the medicine label about giving cough or cold medicine to a child. Do not use the medicine only to make a child sleepy. Death can occur from the misuse of cough or cold medicines in very young children.

Measure liquid medicine carefully. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

You may need to shake the liquid before you measure a dose. Follow all directions on the label.

Swallow the extended-release tablet whole and do not crush, chew, or break it.

Sprinkle the granules directly onto your tongue and swallow right away.

Drink extra fluids to help loosen the congestion and lubricate your throat while you are taking this medicine.

Call your doctor if your symptoms do not improve after 7 days, or if you have a fever, rash, or headaches.

If you need to have any type of surgery, tell the surgeon ahead of time if you have taken this medicine within the past few days.

Store at room temperature away from moisture and heat.

What should I do if I missed a dose of Mucinex DM (Dextromethorphan And Guaifenesin)?

Since dextromethorphan and guaifenesin is used when needed, you may not be on a dosing schedule. Skip any missed dose if it's almost time for your next dose. Do not use two doses at one time.

Overdose Signs

What happens if I overdose on Mucinex DM (Dextromethorphan And Guaifenesin)?

If you think you or someone else may have overdosed on: Mucinex DM (Dextromethorphan And Guaifenesin),  call your doctor or the Poison Control center

(800) 222-1222

If someone collapses or isn't breathing after taking Mucinex DM (Dextromethorphan And Guaifenesin), call 911



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