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Zyrtec vs Claritin: What's the difference?

Zyrtec and Claritin are both antihistamines, but which one is more effective for conditions such as allergic rhinitis or postnasal drip?

Medically reviewed by Drugs.com Last updated on Oct 1, 2018.

Official Answer

by Drugs.com

The difference is Zyrtec is more likely to cause sedation than Claritin. Zyrtec also has a quicker onset of action (one hour vs up to three hours for Claritin) but both last for 24 hours. 

Zyrtec is a brand name for the drug cetirizine and Claritin is a brand name for the drug loratadine. Both cetirizine and loratadine are popular antihistamines with many similarities but there are some important differences.

Which is more sedating? Zyrtec or Claritin

Zyrtec (cetirizine) and Claritin (loratadine) are second-generation antihistamines. Second-generation antihistamines were first developed in the 1990s to provide allergy relief without the unwanted side effect of sedation common to first-generation antihistamines such as promethazine and diphenhydramine. However, it soon became apparent that not all second-generation antihistamines were equal when it came to not causing drowsiness or affecting other thought processes. Cetirizine was significantly more likely than loratadine to cause drowsiness and have a negative effect on motivation in one study of 60 patients with allergic rhinitis.

Which is more effective for Allergic rhinitis?

Trials have shown both Zyrtec and Claritin are significantly more effective than placebo (a pretend pill) for reducing symptoms associated with allergic rhinitis, hay fever, and other allergies. Trials have not consistently shown that one antihistamine is more effective than another, although one trial did report cetirizine reducing symptoms to a greater extent.

Intranasal or ophthalmic (into the eye) antihistamines have a quicker onset of action than oral antihistamines (within about 15 minutes); however, need to be administered several times daily. In people with allergic rhinoconjunctivitis and predominantly eye symptoms, ophthalmic antihistamines work much quicker (within 3 to 15 minutes) and are much more effective than any other form of treatment. Intranasal antihistamines are as effective as intranasal cromolyn, intranasal nedocromil, and leukotriene modifiers in seasonal allergic rhinitis; however, are not as effective at relieving nasal congestion and other symptoms as intranasal glucocorticoids.

Zyrtec Vs Claritin for Urticaria

All second generation antihistamines, including Zyrtec and Claritin, are effective for acute and chronic urticaria, although more trials have been conducted in people with chronic urticaria. No trial has consistently found one antihistamine to be better than another.

Zyrtec Vs Claritin for Postnasal Drip

Post nasal drip may occur for various reasons - allergies (particularly to dairy), colds or flu, various drugs (including birth control pills and high blood pressure tablets), cold temperatures, bright lights, hormonal changes and spicy foods.

Thin postnasal drip secretions caused by allergies may be treated with antihistamines. Second-generation antihistamines such as Zyrtec and Claritin may offer better relief than older-type antihistamines such as promethazine (older antihistamines tend to thicken post-nasal secretions). Intranasal antihistamines, such as azelastine, have a faster onset of action (15 minutes) and appear more effective than oral antihistamines although require more frequent administration. Other treatments include decongestants, cromolyn, and corticosteroid nasal sprays.

In the treatment of post nasal drip caused by nonallergic causes, oral second-generation antihistamines are not very effective. However, the intranasal antihistamine azelastine is effective. Azelastine improves all rhinitis symptoms including nasal congestion, postnasal drip, sneezing and sleeping difficulty. The most common side effect is a metallic after taste; however, this is more likely at higher dosages and tends to dissipate with continued use.

If thin nasal mucus secretions become thick and turn yellow or green, bacterial infection is likely and a doctor should be seen to obtain antibiotics.

Zyrtec Vs Claritin To Relieve Cold Symptoms

Second-generation antihistamines (such as Zyrtec and Claritin) have limited effectiveness at relieving symptoms of cold such as runny nose and sneezing (only 45% of adults felt better after using them compared to 35% with placebo [a pretend pill]). Effects were only noticeable if used within the first two days of a cold, use of antihistamines made no difference thereafter.

Zyrtec Vs Claritin: Administration

The antihistamine effects of Zyrtec and Claritin last for at least 24 hours, therefore, they are both given once daily. Cetirizine, the active ingredient of Zyrtec works within one hour. Claritin may not reach its peak effect for two to three hours since most of its antihistamine activity is attributable to its active metabolite desloratadine, which loratadine is metabolized to in the liver.

Zyrtec Vs Claritin: Side Effects and Interactions

Claritin is unlikely to cause CNS side effects such as sedation, or confusion when used at dosages of 10mg/day. Side effects may be more likely when used at higher dosages. Zyrtec is 3.5 times more likely than Claritin to cause sedation, particularly when used at dosages higher than 10mg/day. However, Zyrtec is still much less sedating than older antihistamines such as promethazine.

Side effects are generally mild with second-generation antihistamines and include a headache and rarely dry mouth, and nausea. All the second generation antihistamines currently on the market appear free from adverse cardiovascular effects. Few major interactions have been reported with either Zyrtec or Claritin; however, there is the possibility that side effects such as sedation, confusion, and mental alertness may be enhanced if given with other drugs with this side effect. More studies are needed to determine if there are any interactions between second generation antihistamines and herbal products or food. Always speak with your doctor of pharmacist before using any drugs in combination.

Bottom Line

Zyrtec and Claritin are both second generation antihistamines with low risk of sedation; however, Zyrtec is more likely to cause sedation than Claritin. Zyrtec also has a quicker onset of action (one hour vs up to three hours for Claritin) but both last for 24 hours. Studies have shown equal effectiveness for Zyrtec and Claritin for allergic rhinitis and urticaria. Studies have not compared the effects of Zyrtec and Claritin for conditions such as postnasal drip, but research suggests intranasal antihistamines such as azelastine are more effective.

See also: Drugs.com Compare Tool - Claritin vs Zyrtec

References

  • Salmun LM, Gates D, Scharf M, et al.Loratadine versus cetirizine: assessment of somnolence and motivation during the workday.Clin Ther. 2000 May;22(5):573-82.
  • Day JH, Briscoe M, Widlitz MD. Cetirizine, loratadine, or placebo in subjects with seasonal allergic rhinitis: effects after controlled ragweed pollen challenge in an environmental exposure unit. J Allergy Clin Immunol. 1998 May;101(5):638-45.
  • Simon FER, Simons KJ. H1 Antihistamines: Current Status and Future Directions. The World Allergy Organization Journal. 2008;1(9):145-155. doi:10.1186/1939-4551-1-9-145.
  • Day JH, Briscoe M, Rafeiro E, et al. Comparative onset of action and symptom relief with cetirizine, loratadine, or placebo in an environmental exposure unit in subjects with seasonal allergic rhinitis: confirmation of a test system.Ann Allergy Asthma Immunol. 2001 Dec;87(6):474-81.
  • Simon FER, Simons KJ. H1 Antihistamines: Current Status and Future Directions. The World Allergy Organization Journal. 2008;1(9):145-155. doi:10.1186/1939-4551-1-9-145.
  • Simon FER, Simons KJ. H1 Antihistamines: Current Status and Future Directions. The World Allergy Organization Journal. 2008;1(9):145-155. doi:10.1186/1939-4551-1-9-145.
  • Slater JW1, Zechnich AD, Haxby DG.Second-generation antihistamines: a comparative review.Drugs. 1999 Jan;57(1):31-47. http://www.ncbi.nlm.nih.gov/pubmed/9951950.
  • Post-Nasal Drip. American Academy of Otolaryngology - Head and Neck Surgery. http://www.entnet.org/content/post-nasal-drip
  • Sharma M, Bennett C, Cohen SN, Carter B. H1-antihistamines for chronic spontaneous urticaria. Cochrane Database of Systematic Reviews 2014, Issue 11. Art. No.: CD006137. DOI: 10.1002/14651858.CD006137.pub2

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