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Cetirizine (su-TEER-a-zeen)


Cetirizine is an antihistamine used to treat allergies such as hay fever. It alleviates symptoms of runny nose, itchy, red, watery eyes, and sneezing.

Zyrtec has also been found to be helpful against hives and itching of the skin.

Cetirizine works by blocking histamines released in the body in response to allergens. When it was introduced, it was not expected to cause sedation. At effective doses, however, cetirizine may make many people feel drowsy. A closely related drug, levocetirizine (Xyzal) is available only by prescription in the US.

Side Effects and Interactions

The most common side effects of Zyrtec include drowsiness, dry mouth, fatigue, and dizziness. Constipation, nausea, headache, sore throat and cough are not unusual. Rare side effects may include tremor, increased appetite, weight gain, ringing in ears, muscle pain, skin rash, hair loss, and liver enzyme elevations. Report any symptoms to your physician promptly, but especially such potentially serious side effects as

  • Confusion, restlessness, hyperactivity
  • Fast, pounding, or uneven heartbeat
  • Sleep problems, weakness, uncontrollable shaking
  • Vision problems
  • Urinating less than usual or not at all

Be aware that it may be difficult to discontinue cetirizine if it has been taken continuously for some time. Many people experience intolerable itching for several weeks if they stop the drug abruptly.

Drug interactions are apparently uncommon, though alcohol and nervous system depressants could add to the sedative action of cetirizine.

Special Precautions

Older people and those with kidney or liver problems may not eliminate cetirizine efficiently and will likely need a lower dose.

Because this antihistamine may cause drowsiness it could make driving dangerous. This is also true for any task that requires mental alertness.

Do not drink alcohol or take other sedating drugs, as it could add to this effect.

Taking the Medicine

Food has very little impact on cetirizine absorption and consequently this medicine can be taken once a day at a time that is convenient.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.”.
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