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Key takeaways
Claritin and Zyrtec are in the same therapeutic class of antihistamine medicines, and it is not recommended that they be taken together or within the same 24-hour period.
Combining Claritin and Zyrtec is not likely to provide better relief from allergy symptoms and may increase the risk of undesirable side effects, such as drowsiness.
There are other allergy medicine combinations that may provide greater relief than an antihistamine alone, such as an antihistamine combined with a decongestant or the combination of an antihistamine with a nasal spray.
If alternating between taking Claritin and Zyrtec, it is recommended to wait 12 to 24 hours between doses (time-lapse dependent on the dosage form of Claritin).
Claritin (generic name loratadine) and Zyrtec (generic name cetirizine) are both over-the-counter (OTC) medicines commonly taken to treat allergy symptoms of hay fever, also known as seasonal allergies and hives (urticaria). They both temporarily relieve itchy and watery eyes, runny nose (allergic rhinitis), sneezing, and itching of the nose or throat. Antihistamines work by reducing the production of a natural substance in the body called histamine, which is responsible for causing allergic reactions when the body is exposed to allergens, such as pollen.
Both Claritin and Zyrtec, along with Allegra (fexofenadine) and Xyzal (cetirizine), are classified as second-generation antihistamines. Notably, these newer antihistamines cause less central nervous system (CNS) side effects, such as drowsiness and sedation, compared to allergy medications known as first-generation antihistamines, such as Benadryl (diphenhydramine).
Can you take Claritin and Zyrtec together?
Although Claritin and Zyrtec are chemically different antihistamines, they are in the same drug class and share a similar blocking action on the histamine receptors. Because of these similar mechanisms of action, it is not recommended that they be taken together other than on direct medical advice from a healthcare provider.
High doses of antihistamines beyond the recommended dose are not likely to provide better relief of allergic symptoms but may increase the risk of undesirable, particularly sedating, side effects. Other potential side effects of Claritin and Zyrtec, alone or combined, include:
- Fatigue
- Dizziness
- Dry mouth
- Headache
- Stomach pain
- Nervousness
- Diarrhea
- Constipation
- Cough
- Nausea
- Dry eyes
Serious side effects that may require immediate medical attention may include:
- Abnormal heart rate
- Palpitations
- Blood pressure disturbances
- Severe faintness
- Confusion
- Hypersensitivity (allergic) reaction to inactive or active ingredients
Although it is not recommended to take Claritin and Zyrtec together or within the same day, there are other allergy medicine combinations that can provide greater allergy relief. An antihistamine combined with a decongestant, such as pseudoephedrine (the active ingredient in Sudafed), provides additional help with nasal congestion and sinus pressure. Both Claritin and Zyrtec come in a combination form that includes pseudoephedrine under the brand names Claritin-D and Zyrtec-D. Another combination of allergy medicines to consider would be Claritin or Zyrtec with a steroid nasal spray, such as Flonase (fluticasone). This combination may be appropriate for some allergy sufferers depending on the clinical symptoms and the response to treatment.
What are the drug interactions between Claritin and Zyrtec?
It is important to note that while there have been no drug interactions reported if Claritin and Zyrtec are taken together, taking both either together or within the same 24-hour period may result in an increased likelihood of adverse events without the benefit of increased symptom relief.
How long after taking Claritin can I take Zyrtec?
Zyrtec is only available as an extended dosage form that is effective for 24 hours. Therefore, it is not recommended to take both Claritin and Zyrtec within the same 24-hour period. When switching from one allergy med to the other, wait at least 24 hours after taking Zyrtec, at least 12 hours when taking the 12-hour dosage form of Claritin, or 24 hours when taking the 24-hour dosage form of Claritin.
Because both are considered less sedating, Claritin and Zyrtec can be taken at any time of the day, including in the morning. Some may experience drowsiness with one or both products, so for those people it may be best to take their dose in the evening.
