Carbetapentane is a cough suppressant. It affects the signals in the brain that trigger cough reflex.

Guaifenesin is an expectorant. It helps loosen mucus congestion in your chest and throat, making it easier to cough out through your mouth.

Allfen CX is a combination medicine used to treat stuffy nose, cough, and chest congestion caused by the common cold or flu.

Allfen CX will not treat a cough that is caused by smoking, asthma, or emphysema.

Allfen CX may also be used for purposes not listed in this medication guide.

Do not use Allfen CX 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. Do not use in larger or smaller amounts or for longer than recommended. Cough or cold medicine is usually taken only for a short time until your symptoms clear up.

Do not give this medication to a child younger than 4 years old. Always ask a doctor before giving a cough or cold medicine to a child. Death can occur from the misuse of cough and cold medicines in very young children.

Take Allfen CX with a full glass of water. Drink extra fluids to help loosen the congestion and lubricate your throat while you are taking this medication.

Allfen CX may be taken with food if it upsets your stomach.

Do not crush, chew, or break an extended-release tablet. Swallow it whole.

Call your doctor if your symptoms do not improve after 7 days of treatment, or if you have a fever with a headache, cough, or skin rash.

This medicine can cause unusual results with certain medical tests. Tell any doctor who treats you if you have taken a cough medicine within the past few days.

If you need surgery, tell the surgeon ahead of time if you have taken a cough medicine within the past few days.

Store at room temperature away from moisture, heat, and light. Do not allow liquid medicine to freeze.

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

You should not use this medicine if you are allergic to carbetapentane or guaifenesin.

To make sure Allfen CX is safe for you, tell your doctor if you have:

• asthma, emphysema, or other breathing problems;

• heart disease or high blood pressure;

• glaucoma;

• diabetes;

• an enlarged prostate or urination problems; or

• overactive thyroid.

It is not known whether Allfen CX will harm an unborn baby. Tell your doctor if you are pregnant.

Carbetapentane and guaifenesin can pass into breast milk and may harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

Artificially sweetened liquid cough or cold medicine may contain phenylalanine. If you have phenylketonuria (PKU), check the medication label to see if the product contains phenylalanine.

Since cough or cold medicine is taken when needed, you may not be on a dosing schedule. If you are on a schedule, use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra medicine to make up the missed dose.

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

This medication may cause blurred vision and may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert and able to see clearly.

Drinking alcohol can increase drowsiness caused by Allfen CX.

Ask a doctor or pharmacist before using any other cold, cough, or allergy medicine. Cough suppressants and expectorants are contained in many combination medicines. Taking certain products together can cause you to get too much of a certain drug. Check the label to see if a medicine contains a cough suppressant or expectorant.

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

This medication may cause serious side effects. Stop using this medication and call your doctor at once if you have:

• confusion, hallucinations, feeling restless or nervous;

• tremors; or

• extreme weakness.

Common side effects of Allfen CX may include:

• drowsiness, dizziness;

• headache;

• sleep problems (insomnia); or

• nausea.

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.

Taking Allfen CX with other drugs that make you sleepy or slow your breathing can worsen these effects. Ask your doctor before taking Allfen CX with a sleeping pill, narcotic pain medicine, muscle relaxer, or medicine for anxiety, depression, or seizures.

Other drugs may interact with carbetapentane and guaifenesin, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.