Question: how long do i have to wait to take another zyrtec?
Answer: A: I have reviewed your question regarding Zyrtec (cetirizine). The normal adult dose is 5mg to 10mg taken at the same time each day. I cannot recommend taking more than the recommended dosage. Studies show that the 1/2 life of Zyrtec (half of the medication still in the body and not eliminated) is around 8 hours.