Cetirizine vs. Loratadine

Cetirizine vs. Loratadine

What is the difference between cetirizine (Zyrtec) and loratadine (Claritin)?

  • Cetirizine and loratadine are non-drowsy antihistamines used to treat symptoms of cold or allergies, including symptoms of seasonal hay fever (allergic rhinitis) such as sneezing, runny nose, and red/watery/itchy eyes.
  • Brand names for Cetirizine include  Zyrtec, Zyrtec Allergy, Children’s Zyrtec Allergy, Children’s Zyrtec Hives Relief, PediaCare Children’s 24 Hour Allergy, Aller-Tec, and Wal-Zyr. Brand names for loratadine include Claritin, Claritin RediTabs, Alavert, Claritin Hives Relief, Children’s Claritin, and others.
  • Both cetirizine and loratadine are available over-the-counter (OTC) and in generic form.
  • Side effects of cetirizine and loratadine that are similar include drowsiness, dry mouth, headache, and fatigue.
  • Side effects of cetirizine that are different from loratadine include nausea, jitteriness, and sore throat.
  • Side effects of loratadine that are different from cetirizine include nervousness and difficulty sleeping.

What are cetirizine and loratadine?

Cetirizine (Zyrtec) is a non-sedating antihistamine. It is similar to other second-generation antihistamines including loratadine (Claritin), fexofenadine (Allegra) and azelastine (Astelin).

  • Histamine is a chemical responsible for many of the signs and symptoms of allergic reactions such as swelling of the lining of the nose, sneezing, and itchy eyes.
  • Certirizine blocks one type of receptor for histamine (the H1 receptor) and prevents activation of H1 receptor-containing cells by histamine.
  • Unlike first generation antihistamines, cetirizine and other second-generation antihistamines do not readily enter the brain from the blood so they cause less drowsiness though cetirizine may cause more drowsiness than other second-generation antihistamines.

Loratadine (Claritin) is a long-acting, non-sedating antihistamine used to treat allergies.

  • Loratadine blocks one type of histamine receptor (the H1 receptor) and thus prevents activation of cells with H1 receptors by histamine.
  • Unlike some antihistamines, loratadine does not enter the brain from the blood and does not cause drowsiness when taken at recommended doses.

What are the side effects of cetirizine (Zyrtec) and loratadine (Claritin)?

Cetirizine side effects

Side effects that have been reported with cetirizine include:

Other important but rare side effects include:

Loratadine side effects

The most common adverse events with loratadine are:

Nervousness and difficulty sleeping have also been reported.

What is the dosage for cetirizine vs. loratadine?

Cetirizine dosage

The recommended dose for adults and children 6 years of age and older is 5 to 10 mg daily depending on the severity of symptoms.

Loratadine dosage

The usual dose of loratadine is 10 mg daily for adults and children older than six years of age. The dose for children 2 to 6 years of age is 5 mg daily.


Common Allergies: Symptoms and Signs See Slideshow

What drugs interact with cetirizine and loratadine?

Cetirizine drug interactions

Theophylline (Theo-Dur, Respbid, Slo-Bid, Theo-24, Theolair, Uniphyl, Slo-Phyllin)reduces the breakdown of cetirizine by 16% and can increase blood levels of cetirizine. Drugs that cause drowsiness may add to drowsiness resulting from cetirizine.

Loratadine drug interactions

Erythromycin, cimetidine (Tagamet), and ketoconazole (Nizoral) increase the blood concentration of loratadine by inhibiting the elimination of loratadine. This may result in increased adverse events from loratadine.

St. John’s wort, carbamazepine (Tegretol, Tegretol XR , Equetro, Carbatrol, Epitol, Teril), and rifampin reduce blood levels of loratadine.

Are cetirizine and loratadine safe to use while pregnant and breastfeeding?


Cetirizine has not been adequately evaluated in pregnant women. Available evidence suggests that risk to the developing fetus is low.

Cetirizine is excreted in human breast milk.


Loratadine is secreted in breast milk at levels similar to blood levels. Nursing mothers should decide whether to stop breastfeeding or discontinue loratadine.

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Medically Reviewed on 12/7/2021


FDA Prescribing Information