Detailed Cetirizine dosage information for adults, the elderly and children. Includes dosages for Allergic Rhinitis and Urticaria; plus renal, liver and dialysis adjustments. Overview: Cetirizine is an antihistamine that is taken to help treat allergy symptoms, such as a runny nose, itchy or watery eyes, sneezing, or an itchy nose or throat. It may also be used to... Take as directed by the doctor and in doses and duration as prescribed. Side effects of the medicine are drowsiness, headache, weakness, and dry mouth. Most of them are temporary but if you feel the side effects persist or your condition worsens, you should contact the doctor immediately. MAJOR® Compare to active ingredient in Zyrtec® Original Prescription Strength - Cetirizine - Hydrochloride Tablets, 10 mg/Antihistamine - All Day Allergy Relief - INDOOR & OUTDOOR ALLERGIES - 24 HOUR ...