Recently I was prescribed Xyzal (levocetirizine) for an unknown rash/hives recurring around my eyes. I read that Xyzal should not be taken with ritonavir (Norvir, Kaletra). I am on the Atripla combination. After reading this warning it scared me and i prefer not to take the Xyzal. At the same time I would like to figure out this annoying skin problem so I can stop using a cortizone cream. Is it ok to take this antihistamine while on Atriple? or don't risk it. Why do anitihistamines generally give this warning about ritonavir? ( Also the rash is unrelated to the Atripla because I started getting it a year before starting haart/atripla) Thanks for your help!

In general, Ritonavir can increase the levels of antihistamines, some more so than others and with differing impact in terms of clinical relevance (in particular high levels of ceratain antihistamines can lead to cardiac rhythm disturbances). But there appears to be no clinically significant drug interaction between ritonavir and Xyzal (or levocetirizine). Moreover, there is no significant interaction between Xyzal and efavirenz (one of the components of Atripla). Thanks, Joe