Xyzal Tablets (levocetirizine) | An antihistamine often referred to as third-generation, with fewer drawbacks

Xyzal Tablets are one of the most advanced antihistamines, often referred to as third-generation, with levocetirizine as the main ingredient. Compared with Allegra Tablets, which are also often referred to as third-generation, they have the advantage of simpler dosing instructions.¹

Compared with first-generation antihistamines, they cause less drowsiness and fewer anticholinergic adverse effects, and can be taken once daily regardless of meals.

Less drowsy than first-generation

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First-generation antihistamines, such as Peniramin Tablets and Adipam Tablets, cross the blood–brain barrier and strongly block H1 receptors in the brain. This can cause sleepiness and slower reactions.

In contrast, levocetirizine in Xyzal Tablets does not readily cross the blood–brain barrier. In a study in which eight healthy adults took a single dose with the same ingredient and dose as Xyzal Tablets, mean brain H1 receptor occupancy was 8.1%, with no significant difference from placebo.²

A pooled analysis of 48 studies (18,014 participants) also found that levocetirizine caused less sedation and less change in reaction time than first-generation antihistamines. However, it caused slightly more sedation than placebo. This means Xyzal Tablets may still cause drowsiness depending on the individual.³

Fewer anticholinergic adverse effects as well

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First-generation antihistamines act not only on H1 receptors but also on muscarinic receptors. As a result, anticholinergic adverse effects such as dry mouth, constipation, difficulty urinating, and blurred vision may occur.

In contrast, levocetirizine in Xyzal Tablets has high selectivity for H1 receptors and does not bind well to muscarinic receptors, so it has fewer anticholinergic adverse effects that are problematic with first-generation agents.⁴

For more details on differences by antihistamine generation and adverse effects, please refer to the antihistamine article.

Xyzal’s lineage and comparison with Zyrtec Tablets

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Hydroxyzine in Adipam Tablets, a first-generation agent, is metabolized in the body into cetirizine in Zyrtec Tablets, a second-generation agent. Cetirizine is a mixture of two stereoisomers that are mirror images of each other. Levocetirizine, the ingredient in Xyzal Tablets often referred to as third-generation, is made by selecting only the R-isomer, which primarily acts on H1 receptors.⁵

However, the structural difference of isolating only the R-isomer—responsible for most of the effect in Zyrtec Tablets—does not necessarily indicate clinical superiority.

In a trial in 570 patients with allergic rhinitis who received a single dose of levocetirizine 5 mg or cetirizine 10 mg, there was no significant difference in symptom improvement. Because the study assessed responses after a single pollen exposure, it cannot determine long-term outcomes, but at least in the short term it did not conclude that Xyzal is superior to Zyrtec.⁶

In a study comparing the two drugs in 29 patients with allergic rhinitis who had experienced drowsiness with cetirizine, there was also no significant difference in drowsiness.⁷ The 2026 allergic rhinitis guidelines also classify the degree of sedation for both cetirizine and levocetirizine as moderate.⁸

The most practical difference is their regulatory classification. Zyrtec Tablets are an over-the-counter medicine and can be purchased without a prescription, whereas Xyzal Tablets are a prescription medicine and require a prescription.^1,9

In addition, Xyzal is available as a syrup (Xyzal Oral Solution), which can be used in young children. However, Xyzal Oral Solution is also a prescription medicine, so a prescription is required.¹⁰

Xyzal Tablets from age 6; Xyzal Oral Solution from age 1

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Xyzal Tablets can be taken from age 6 and older. For children under 6, Xyzal Oral Solution should be used, and it can be taken from age 1. The two products contain the same ingredient, but the dose and frequency differ by age.^1,10

Product	Age	Single dose	Dosing frequency
Xyzal Tablets	Age 6 and older	1 tablet	Once daily
Xyzal Oral Solution	Age 6 and older	10 mL	Once daily
Xyzal Oral Solution	Age 2 to under 6	2.5 mL	Twice daily
Xyzal Oral Solution	Age 1 to under 2	2.5 mL	Once daily

Difference vs Allegra Tablets: simpler dosing

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Allegra Tablets, which are also often referred to as third-generation along with Xyzal Tablets, may have up to a 20% reduction in the amount absorbed by the body when taken with a high-fat meal.¹¹ Absorption may also be significantly reduced when taken with grapefruit juice, orange juice, or apple juice, or when taken with antacids containing aluminum or magnesium.^12,13,14

In contrast, Xyzal Tablets do not require complex conditions involving meals, fruit juice, or antacids. When taken with food, the absorption rate slows, but the total amount absorbed does not decrease.¹

Dosing conditions	Xyzal Tablets	Allegra Tablets
Dosing frequency	Once daily	Once or twice daily depending on strength
Meals	No restrictions	Before meals
Beverages taken with the medicine	No restrictions	Must not be taken with grapefruit juice, orange juice, or apple juice
Antacids	No restrictions	Keep about a 2-hour interval from aluminum/magnesium antacids

For more details on dosing by strength and precautions for Allegra Tablets, please refer to the Allegra Tablets article.

Kidney function and drowsiness should be checked

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Because levocetirizine in Xyzal Tablets is primarily eliminated through the kidneys, adults should extend the dosing interval if their glomerular filtration rate (GFR), an indicator of kidney function, is below 60 mL/min.^1,10

Below is dosing guidance for Xyzal Tablets based on GFR. In children, kidney function and body weight must be considered together, so it cannot be summarized as simply as in the table below.¹⁰

GFR (mL/min)	Kidney function	Dosing
60 or higher	Normal or mildly decreased	Once daily
30 to under 60	Moderately decreased	Once every 2 days
15 to under 30	Severely decreased	Once every 3 days
Under 15 or on hemodialysis	End-stage kidney disease	Do not take

Independently of kidney function, drowsiness should also be checked. If you are taking Xyzal for the first time, it is safest to avoid driving or operating machinery until you know how drowsy it makes you. Alcohol or medicines that cause drowsiness can increase drowsiness, so use caution when taking them together.¹

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References

1. Ministry of Food and Drug Safety (MFDS), approval information for Xyzal Tablets 5 mg, accessed 2026-08-24.
2. Tashiro M, Mochizuki H, Iwabuchi K, et al. Brain histamine H1 receptor occupancy measured by PET after oral administration of levocetirizine, a non-sedating antihistamine. Expert Opin Drug Saf. 2015;14(2):177-185. PMID 25466429. DOI 10.1517/14740338.2015.989831.
3. Snidvongs K, Seresirikachorn K, Khattiyawittayakun L, Chitsuthipakorn W. Sedative Effects of Levocetirizine: A Systematic Review and Meta-Analysis of Randomized Controlled Studies. Drugs. 2017;77(2):175-186. PMID 28070872.
4. Devillier P, Roche N, Faisy C. Clinical pharmacokinetics and pharmacodynamics of desloratadine, fexofenadine and levocetirizine: a comparative review. Clin Pharmacokinet. 2008;47(4):217-230. PMID 18336052.
5. Chen C. Physicochemical, pharmacological and pharmacokinetic properties of the zwitterionic antihistamines cetirizine and levocetirizine. Curr Med Chem. 2008;15(21):2173-2191. PMID 18781943.
6. UCB Clinical Study Summary A00379. NCT00544388. Report date 2007-07-20. Accessed 2026-08-25.
7. Tzanetos DB, Fahrenholz JM, Scott T, Buchholz K. Ann Allergy Asthma Immunol. 2011;107(6):517-522. PMID 22123381. DOI 10.1016/j.anai.2011.08.012.
8. Vieira RJ, Sousa-Pinto B, Bousquet J, et al. Allergic Rhinitis and Its Impact on Asthma (ARIA)-EAACI Guidelines-2024-2025 Revision: Part II-Guidelines on Oral and Ocular Treatments. Allergy. 2026;81(6):1947-1970. PMID 41877472.
9. Ministry of Food and Drug Safety (MFDS), approval information for Zyrtec Tablets, accessed 2026-08-16.
10. Xyzal Oral Solution product information, Korea Pharmaceutical Information Center (KPIC) · MFDS approval data, accessed 2026-08-25.
11. Fexofenadine hydrochloride tablets approval information, DailyMed, accessed 2026-08-22.
12. Allegra Tablets 120 mg product information, KPIC · MFDS approval data.
13. Allegra Tablets 180 mg approval information · medication guide, KPIC · MFDS approval data, accessed 2026-08-22.
14. Allegra Tablets 30 mg approval information · medication guide, KPIC · MFDS approval data, accessed 2026-08-22.