Difference Between Zyrtec and Claritin


Main Difference

The main difference between Zyrtec and Claritin is that Zyrtec is the brand name of cetirizine hydrochloride and Claritin is the brand name of loratadine hydrochloride.

Zyrtec vs. Claritin

Zyrtec contains cetirizine hydrochloride while Claritin contains loratadine hydrochloride. Zyrtec starts to show its therapeutic action after 59-126 minutes of dose whereas starts to show its therapeutic action after 102 minutes of dose Claritin Zyrtec has a duration of action of 12-24 hrs on the other hand Claritin has a duration of action of 24hrs. Zyrtec is available in the strength of 5-10mg, whereas Claritin is available in the strength of 10mg. Zyrtec is not metabolized by the cytochrome P450 enzyme system while Claritin is metabolized by the cytochrome P450 enzyme system. Zyrtec is piperazine antihistamine whereas Claritin is piperidine antihistamines. Zyrtec does not interact with cytochrome P450 enzyme inducers or inhibitors while Claritin interacts with cytochrome P450 enzyme inducers or inhibitors. Zyrtec does not have active metabolite, on the other hand, Claritin has active metabolite.


Comparison Chart

Zyrtec is antihistamine containing cetirizine hydrochloride as an active therapeutic agent.Claritin is antihistamine-containing loratadine hydrochloride as an active therapeutic agent.
Drug Category
Receptors at Which Drug Acts
H1 receptorsH1 receptors
Mode of Action
Block H1 receptorsBlock H1 receptors
Duration of Action
Tablets, SyrupsTablets, Suspensions, Syrups
Therapeutic Uses
Runny nose
Itching of eyes or nose
Allergic rhinitis
Hay fever
Adverse Effects
Dry mouth
Antimuscarinic effects
Minute sedation
Minute psychomotor retardation

What is Zyrtec?

Zyrtec is the antihistamine and is the brand name of cetirizine hydrochloride. Zyrtec belongs to the 2nd generation of antihistamine. Zyrtec is used to treat the symptoms of allergy, which includes the sneezing, itching in the eyes or nose, runny nose, and hives. Zyrtec blocks the pharmacological actions of the histamine, which is a natural substance and releases in response to exposure to any other type of allergen. Zyrtec does not prevent or treats a severe allergic reaction such as anaphylaxis. Cetirizine in Zyrtec is selective H1 receptor blocker. Cetirizine has 600 times more selectivity for the H1 receptors than any other type of receptors. Only a little amount of Cetirizine cross the blood-brain barrier so it causes less sedation. 10mg of Cetirizine occupies approximately 12% H1 receptors, 20mg of Cetirizine occupies approximately 25% H1 receptors, and 30mg of Cetirizine occupies approximately 67 % H1 receptors in the brain. Cetirizine also inhibits eosinophil chemotaxis. Cetirizine in Zyrtec is rapidly absorbed after oral administration having the oral bioavailability of 70%. Zyrtec starts showing its pharmacological actions after 20 minutes of dose. Cetirizine is not extensively metabolized and even not metabolized by cytochrome-P450 enzyme system, so it does not show any drug-drug interaction with drugs which are cytochrome-P450 enzyme inducers or inhibitors. Cetirizine in Zyrtec is metabolized through the oxidation and conjugation. Cetirizine in Zyrtec is excreted 70-85% in the urine and 10-13% in feces. Zyrtec is an over the counter drug. Zyrtec dosage depends upon patient age, medical condition, and the response of treatment. If the symptoms of allergy or hives persist after three-day treatment of Zyrtec have a visit of a doctor. The adverse effects of Zyrtec are dry mouth, dizziness, and tiredness. Zyrtec overdose may cause difficulty breathing. Zyrtec is not prescribed to hydroxyzine allergic patients.


What is Claritin?

Claritin is the antihistamine and is the brand name of the loratadine hydrochloride. Claritin belongs to the 2nd generation of the antihistamines. Claritin is used to treat hives and allergic rhinitis. Claritin resembles in structure to TCA and antipsychotic quetiapine. Claritin is taken orally. Loratidine in Claritin is a tricyclic antihistamine and acts as an inverse agonist at peripheral H1 receptors. Claritin is absorbed from GIT rapidly when taken orally and quickly undergoes the first pass hepatic metabolism. Claritin is metabolized by the cytochrome P450 enzyme system. 90-97% of loratadine in Claritin is plasma protein bound. Claritin when metabolized, its metabolite desloratadine 73-76% binds to plasma proteins, and desloratadine is also responsible for the effects of the antihistamine of Claritin. Peak plasma concentration of Claritin is reached in 1-2 hrs, and half-life of Claritin is round about 8hrs, and along with the half-life of desloratadine it is 27hrs. Claritin is excreted in urine and a little amount in feces. Unmetabolized Claritin is also excreted in the urine. Claritin does not prevent or treat hives or allergic reactions. Claritin tablets or capsules should not be used in children under the age of 6. Claritin chewable tablets or liquids should not be used without prescription in the children under the age of 2. Claritin is over the counter drug. Claritin can be taken with or without food; if Claritin is taken in liquid form, then its dose should be measured with measuring spoon. The dose of Claritin can be adjusted according to age and severity of the allergy; dose can also be adjusted according to the response of treatment. Claritin should not be used if the patient is allergic to the active drug loratadine or active metabolite desloratadine. Claritin in recommended doses does not cause drowsiness, but it is recommended do not operate machinery after taking it.


Key Differences

  1. Zyrtec has cetirizine hydrochloride as an active therapeutic agent while Claritin has loratadine hydrochloride as an active therapeutic agent.
  2. Zyrtec produces therapeutic effects for 12-24 hrs while Claritin produces therapeutic effects for 24 hrs
  3. Zyrtec has the onset of action of 59minutes-126 minutes, whereas Claritin has the onset of action of 102 minutes.
  4. Zyrtec does not undergo metabolism by the cytochrome P450 enzyme system whereas Claritin undergoes metabolism by the cytochrome P450 enzyme system.
  5. Zyrtec is piperazine chemically whereas Claritin is piperidine chemically.
  6. Zyrtec does not have active metabolite while Claritin has an active metabolite
  7. Zyrtec is available as tablet and syrup whereas Claritin is available as tablet, syrup, and suspension.
  8. Zyrtec available strength is 5-10mg while Claritin available strength is 10mg.


The main conclusion of the above discussion is that both Zyrtec and Claritin are used for the treatment of allergies.

Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White

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