Cetirizine hydrochloride versus levocetirizine dihydrochloride?

Question

Usually, I'm prescribed levocetirizine (Xyzal) to treat my year-long allergies. I went to the doctor yesterday, and she prescribed me cetirizine instead. I'm not sure whether this was an accident (I specifically said I wanted levo) or whether she had decided, without telling me, to change my medication.

What are the main differences between the two? I've tried lots of different types of antihistamines over the years, and Xyzal seems to work the best (none of them prevent my allergic reactions, but some supress it more than others)

Answer 1

This is only partly true.  Molecules can have handedness (their shape is not symmetric, so a left and a right-handed version can exist.  Research suggests, and my own experience says that levocetirizine (a non-mixture of (say) the  left-handed version) is better than cetirizine, which is a mixture of both.  Sure, cetirizine is cheaper, but levocetirizine works, whereas at best, cetirizine may be 50% effective, or may simply be a sub-clinical dose, and not work.  Do the research yourself - look for cetirizine levocetirizine differences.  Tell doc not to be a cheapskate.