Can we use zyrtic morning or evening?

Zyrtec (cetirizine): Because the most prominent side effect of zyrtec (cetirizine) is drowsiness, i typically recommend that adults try it in the evening, so that if there is drowsiness, the impact of that drowsiness will be limited because you should be going to bed anyway. If there is limited drowsiness, you could certainly take it during the day, but try an evening dose first to see how your body reacts to it.