https://www.zyrtec.com/products/zyrtec-tablets
Adults and children 6 years and over:
One 10 mg tablet once daily; do not take more than one 10 mg tablet in 24 hours. A 5 mg product may be appropriate for less severe symptoms.
https://zhidao.baidu.com/question/38414003.html
【用法用量】口服:成人或12岁以上儿童,一次1片,一日1次或遵医嘱。如出现不良反应,可改为早晚各半片。