GENERIC NAME: cetirizine
BRAND NAME: Zyrtec, Zyrtec Allergy, Zyrtec Hives
DRUG CLASS AND MECHANISM: Cetirizine is a non-sedating antihistamine that works by blocking histamine (H-1) receptors on cells. It is similar to the other second generation antihistamines loratadine (Claritin), fexofenadine (Allegra) and azelastine (Astelin). Histamine is a chemical that is responsible for many of the signs and symptoms of allergic reactions, for example, swelling of the lining of the nose, sneezing, and itchy eyes. Histamine is released from histamine-storing cells (mast cells) and then attaches to other cells that have receptors for histamine. The attachment of the histamine to the receptors causes the cells to be "activated," releasing other chemicals that produce the effects that we associate with allergy, for example, sneezing. Certirizine blocks one type of receptor for histamine (the H1 receptor) and thus prevents activation of H1 receptor-containing cells by histamine. Unlike the first generation antihistamines, cetirizine and other second-generation antihistamines do not readily enter the brain from the blood, and, therefore, they cause less drowsiness. Cetirizine may cause more drowsiness than other second generation antihistamines. The FDA approved cetirizine in September 1996.
PRESCRIPTION: Yes, OTC (yes)
GENERIC AVAILABLE: Yes
PREPARATIONS: Tablets: 5 and 10 mg. Tablets (Chewable or orally disintegrating): 10 mg. Syrup: 5 mg/5 ml.
STORAGE: Cetirizine should be stored in a dry place at 15-30 C (59- 86 F).
DOSING: The recommended dose is 5 to 10 mg daily depending on the severity of symptoms.
DRUG INTERACTIONS: Theophylline (Theo-Dur, Respbid, Slo-Bid, Theo-24, Theolair, Uniphyl, Slo-Phyllin)reduces the breakdown of cetirizine by 16% and can increase blood levels of cetirizine. Drugs that cause drowsiness may add to drowsiness resulting from cetirizine.
PREGNANCY: Cetirizine has not been adequately evaluated in pregnant women. Available evidence suggests that risk to the developing fetus is low.
NURSING MOTHERS: Cetirizine is excreted in human breast milk.
SIDE EFFECTS: Sleepiness occurs in 14% of patients. Dry mouth, nausea, headache, fatigue, jitteriness and sore throat are infrequently reported with cetirizine. Allergic reactions, seizures, fainting, and low blood pressure occur rarely.
Medically reviewed by Venkatachala Mohan, MD; Board Certified Internal Medicine with subspecialty in Gastroenterology
Medically Reviewed by a Doctor on 2/14/2014