Dextromethorphan is a cough suppressant. Guaifenesin is an expectorant.

Mucinex DM 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.

Mucinex DM may also be used for purposes not listed in this medication guide.

Do not use this medicine if you have used an MAO inhibitor in the past 14 days, such as isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, or tranylcypromine.

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.

Do not use Mucinex DM 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).

Since Mucinex DM 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.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Avoid driving or hazardous activity until you know how Mucinex DM 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.

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

Mucinex DM may cause serious side effects. Stop using Mucinex DM 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 of Mucinex DM 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.

Avoid using this medicine with other drugs that cause drowsiness or slow your breathing (such as opioid medicine, a muscle relaxer, or medicine for anxiety or seizures).

Ask a doctor or pharmacist before using this medicine if you are also using any other drugs, including prescription and over-the-counter medicines, vitamins, and herbal products. Some medicines can cause unwanted or dangerous effects when used together. Not all possible interactions are listed in this medication guide.