Xyzal, generic levocetirizine, is a fairly new treatment for certain types of allergy such as allergic rhinitis and hives, or chronic idiopathic urticaria. It was launched in parts of Europe in 2001 and was approved in 2007 for certain uses in the USA.
Xyzal, on a chemical level, consists entirely of the levo form of cetirizine. Zrytec, the medication that came first and stopped being on patent, consists of both the levo and dextro form. We discuss later what that actually means.
In terms of action on the body, Xyzal is an anti-histamine, which means it stops the action of histamine, a chemical messenger which is highly involved in causing inflammation and allergies.
Xyzal can also work to treat inflammation and allergic symptoms in other ways, such as directly changing the behavior of certain cells like eosinophils.
Is Xyzal any different than Zyrtec?
As mentioned, Xyzal is basically just a form of Zyrtec.
What does the whole levo/dextro thing mean? Well, imagine that you’re a gigantic drug molecule which is somehow able to see. You’re standing in front of a mirror – so there are two versions of you. Your mirror image is you but flipped over.
In medications sometimes the mirror image is more effective than the other form. Xyzal, then, is just the levo, or “left-handed,” version of the chemical that makes up Zyrtec. It is possible that this makes it more effective. One study showed that Xyzal binds to certain histamine receptors with twice the affinity of Zyrtec.
Critics point out, however, that companies can take an old medication and say that a specific form of it is better, patent that form, and then sell it when their patent runs out on the old medication. One study has shown, in fact, that Zyrtec actually provides longer symptom relief than Xyzal.
Xyzal vs Clarinex
One study of 373 patients showed that Xyzal and Clarinex, a popular allergy medication, worked about as well for nasal congestion and other symptoms of allergies.
Another study showed significant superiority of Xyzal over Clarinex in an artificial setting. That study scratched people with something they were allergic to then waited for them to develop redness and swelling at the spot. This is called a “wheel and flare” test, and is commonly done when testing someone for things they are allergic to.
The study then tested which medication worked best to reduce the wheel and flare response.
There, Xyzal had at least 70% suppression of allergic reaction in everyone within 1-3 hours and lasted for 20 hours. Clarinex, on the other hand, suppressed the allergic reaction in only about 30% of those using it.
On the other hand, there are studies which have shown no difference in Clarinex and Xyzal on the wheel and flare test.
Xyzal’s side effects
As Xyzal reaches the brain at fairly low levels, it may have less side effects related to exhaustion and similar than other medications, particularly the earlier allergy medications.
That said, in one study a very high percentage of people reported some sort of sedation related effect, usually occurring within a week of treatment.
5-6% report somnolence, or feeling very tired
4% report nasopharyngitis or cold
A small amount of people report dry mouth or sore throat.
In children, there may be different side effects:
4% report pyrexia or fever
3% report cough
2% report nose-bleeds
This list is not comprehensive; consult manufacturer’s insert.
Effect on Driving
Xyzal has a warning that people taking it should avoid driving due to its potential to cause sedation. To try to disprove this, researchers did a blind test where people were given either Xyzal or placebo then made to take various driving tests.
That study did not show an impact, but it hasn’t proven compelling enough to change the official labeling.
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