Drug Uses Zyrtec is an antihistamine. Antihistamines prevent sneezing, runny nose, itching and watering of the eyes, and other allergic symptoms. Zyrtec is used to treat allergies, hives (urticaria), and other allergic inflammatory conditions. How Taken Zyrtec comes as a tablet to take it orally. It usually is taken once a day. It may be taken regularly or when allergy symptoms flare up. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take Zyrtec exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor. Warnings/Precautions Before taking this medication, tell your doctor if you have kidney or liver disease. You may need a lower dose or special monitoring during your therapy with Zyrtec. Zyrtec is in the FDA pregnancy category B. This means that it is unlikely to harm an unborn baby. Do not take Zyrtec without first talking to your doctor if you are pregnant. Zyrtec passes into breast milk and may affect a nursing baby. Do not take Zyrtec without first talking to your doctor if you are breast-feeding a baby. If you are over 60 years of age, you may be more likely to experience side effects from Zyrtec. You may require a lower dose of this medication. Missed Dose If you forget to take a dose, do not take an extra tablet to catch up for the dose you forgot. Wait and take your next tablet at the regular time. Do not take more tablets than your doctor prescribed. Possible Side Effects Stop taking Zyrtec and seek emergency medical attention if you experience an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives). Other, less serious side effects may be more likely to occur. Continue to take Zyrtec and talk to your doctor if you experience sleepiness, fatigue, or dizziness; headache; or dry mouth. Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome. Storage Store at 20-25°C (68-77°F); excursions permitted to 15-30°C (59-86°F). Overdose Seek emergency medical attention. Symptoms of a Zyrtec overdose are not well known, but extreme sleepiness, confusion, and weakness may be expected. More Information Use caution when driving, operating machinery, or performing other hazardous activities. Zyrtec may cause dizziness or drowsiness. If you experience dizziness or drowsiness, avoid these activities. Use alcohol cautiously. Alcohol may increase drowsiness and dizziness while you are taking Zyrtec.