Kyle asked
I wanted to know if Xyzal works all day?
Answer
Xyzal (levocetirizine) is a "third-generation" antihistamine, similar to Zyrtec (cetirizine). In fact, Xyzal is the "R-enantiomer" of Zyrec.
Xyzal is used for the following indications:
- Seasonal allergies
- Perennial allergies
- Urticaria (hives)
Xyzal, the only "third-generation" currently available over the counter, has similar properties to "second-generation" antihistamines like Claritin and Allegra. Each dose lasts around 24 hours and while not technically classified as "non-drowsy", causes significantly less drowsiness than "first-generation" antihistamines like Benadryl.
How Long Does Xyzal Last?
Each dose of Xyzal lasts approximately 24 hours in terms of its antihistamine effects. Per the prescribing information, it should be dosed once daily, in the evening, as it may cause slight drowsiness after initially taking.
In terms of how long Xyzal lasts in the body, it is has a half-life round 8-9 hours. It generally takes 5-6 half-lives for a drug to be completely eliminated from the body. Therefore, it will take Xyzal between 40 and 54 hours, or about 2 days, to be completely metabolized.
In those with decreased kidney function, it may take longer for Xyzal to be metabolized.
Additional Information About Xyzal
After taking Xyzal tablets by mouth, peak blood concentrations of Xyzal are reached reached in about 0.9 hours. The oral solution is absorbed faster and reaches maximum concentrations in blood faster than the tablets, about 30 minutes after taking for most individuals.
Xyzal may be taken with or without food but peak blood concentrations are reduced by 36% when taken with food. This isn't thought to reduce the effectiveness of the medication however.
Summary
- The effects of Xyzal last around 24 hours and is therefore indicated to be dosed once daily.
- Based on the half-life of Xyzal, it will be completely metabolized and eliminated from the body in 40-54 hours.
