Cetirizine is an antihistamine that reduces the natural chemical histamine in the body. Histamine can produce symptoms of sneezing, itching, watery eyes, and runny nose.

Pseudoephedrine is a decongestant that shrinks blood vessels in the nasal passages. Dilated blood vessels can cause nasal congestion (stuffy nose).

Zyrtec-D is a combination medicine used to treat cold or allergy symptoms such as nasal and sinus congestion, sneezing, itching, watery eyes, or runny nose.

Zyrtec-D may also be used for purposes not listed in this medication guide.

You should not use Zyrtec-D if you have narrow-angle glaucoma, severe high blood pressure (hypertension), severe coronary artery disease, if you are unable to urinate, or if you are allergic to hydroxyzine (Atarax, Vistaril).

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, phenelzine, rasagiline, selegiline, and 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.

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

Take one tablet every 12 hours, unless your doctor tells you otherwise. You may take this medication with or without food.

Call your doctor if your symptoms do not improve, if they get worse, or if you have also have a fever.

Store at room temperature away from moisture and heat.

You should not use this medicine if you are allergic to cetirizine or pseudoephedrine, or if you have:

• narrow-angle glaucoma;

• severe high blood pressure (hypertension);

• severe coronary artery disease;

• if you are unable to urinate; or

• if you are allergic to hydroxyzine (Atarax, Vistaril).

Do not use Zyrtec-D 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.

Ask a doctor or pharmacist if it is safe for you to take this medicine if you have other medical conditions, especially:

• heart disease, coronary artery disease, high blood pressure, or heart rhythm disorder;

• diabetes;

• a thyroid disorder;

• glaucoma;

• kidney or liver disease;

• an enlarged prostate; or

• problems with urination.

FDA pregnancy category C. It is not known whether Zyrtec-D will harm an unborn baby. Do not use this medicine without a doctor's advice if you are pregnant.

Cetirizine and pseudoephedrine may pass into breast milk and may harm a nursing baby. Antihistamines and decongestants may also slow breast milk production. Do not use this medicine without a doctor's advice if you are breast-feeding a baby.

Older adults may be more likely to have side effects from Zyrtec-D.

Take the missed dose as soon as you remember. If it is almost time for your next dose, wait until then to take the medicine and skip the missed dose. Do not take extra medicine to make up the missed dose.

Seek emergency medical attention if you think you have used too much of Zyrtec-D.

This medication may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Avoid drinking alcohol. It can increase some of the side effects of cetirizine.

Ask a doctor or pharmacist before using any other cold or allergy medicine. Antihistamines and decongestants 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 an antihistamine or decongestant.

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

Zyrtec-D may cause serious side effects. Stop using Zyrtec-D and call your doctor at once if you have:

• fast, pounding, or uneven heartbeat;

• weakness, tremors (uncontrolled shaking)

• severe restless feeling, hyperactivity, extreme feeling of fear or confusion;

• problems with vision;

• little or no urinating; or

• high blood pressure (severe headache, buzzing in your ears, chest pain, shortness of breath, uneven heartbeats).

Common side effects of Zyrtec-D may include:

• dizziness, drowsiness, tired feeling;

• sleep problems (insomnia);

• dry mouth, nausea, stomach pain, constipation; or

• trouble concentrating.

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.

Ask a doctor or pharmacist before using Zyrtec-D 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.

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