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Claritin is the third of a new generation of allergy medicines called histamine H1 receptor antagonists. These nonsedating antihistamines are changing the way doctors control allergy symptoms.

Until these drugs became available, virtually all oral allergy medicines caused some degree of sedation. This made driving or operating machinery dangerous. Nonsedating antihistamines like Claritin now provide many people management of symptoms such as sneezing or hives without reducing alertness or coordination. And unlike other allergy medicine, Claritin does not appear to interact with sedatives.

In one popular prescription product, Claritin-D, loratadine is combined with the decongestant pseudoephedrine for quicker relief of congestion.

Side Effects and Interactions

Side effects with Claritin are not common, but people have reported headache, fatigue, drowsiness and dry mouth. Other potential reactions include weight gain, blurred vision, weakness, dizziness, nausea, anxiety, depression, impotence and menstrual changes. Report any symptoms to your doctor.

For Claritin-D, the most common side effects are headache, insomnia, and dry mouth. Indigestion and loss of appetite are reported in addition to side effects listed for Claritin alone.

Certain drugs can interact with Claritin to raise blood levels of the antihistamine. Nizoral is known to boost blood levels of Claritin, but no changes in heart rhythm or electrocardiogram (ECG) were noted as a result.

In general, it would be wise to check with your doctor or pharmacist if you must take Claritin in combination with a medicine known to interact with the similar drugs, Hismanal and Seldane. These include erythromycin (E.E.S., E-Mycin, ERYCEry-Tab, Erythrocin Stearate, etc.), Biaxin, Sporanox or Tagamet.

The pseudoephedrine component of Claritin-D can reduce the effectiveness of many blood pressure medicines and may interact with Lanoxin.

Check with your pharmacist and physician to make sure Claritin or Claritin-D is safe in combination with any other drug you take.

Special Precautions

Antihistamines should be avoided for several days before allergy skin testing, as they could interfere with the results. People with liver problems should get a reduced dose of Claritin, as they process it less efficiently.

Recent animal research suggests that Claritin and other antihistamines may promote tumor growth. We hope that further research will clarify this risk. People with cancer or at high risk of cancer should discuss this animal data with their physicians.

Claritin-D is not appropriate for people with narrow-angle glaucoma or urinary retention. It should not be taken by anyone on Eldepryl, Nardil, Parnate, or any other MAO inhibitor.

Taking the Medicine

Claritin is a long-acting antihistamine. One tablet daily will provide 24 hour coverage.

Claritin should be taken on an empty stomach, as food substantially interferes with absorption. That means at least one hour before eating or two hours after a meal. Claritin-D is also taken on an empty stomach, but two a day, 12 hours apart, are required for maximum effectiveness.

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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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