Can i drink beer while taking zyrtec (cetirizine)?

NO: And the zyrtec shouldn't be your question, it should be the Klonopin (clonazepam). Benzos and alcohol DO NOT MIX. In fact, alcohol use itself can promote anxiety - it initially will dull it a bit, but then will rebound and it will increase - becomes a vicious cycle. Exactly how much beer are we talking about, and does the prescriber of your Klonopin (clonazepam) know about it? If not, they NEED to know, and soon.