Zyrtec can increase the drowsiness caused by other medications. However, because Zyrtec does not cross the blood-brain barrier, it is less likely to cause drowsiness than first-generation drugs ...

However, an overdose of Zyrtec may cause symptoms such as irritability ... with or without food. If drowsiness occurs, you ...

Dr. Hark also recommends stocking up on over-the-counter allergy medications such as Allegra, Zyrtec ... over-the-counter medications as some can cause drowsiness and raise blood pressure.