Loratadine (brand names Alavert, Claritin, Claritin 24-Hour Allergy, Claritin Hives Relief, Clear-Atadine, ohm Allergy Relief, Tavist ND) is approved by the FDA for use in the treatment of allergic rhinitis and urticaria, or hives.
Cetirizine hydrochloride (brand name Zyrtec) is approved by the FDA for use in the treatment of seasonal and perennial allergic rhinitis and chronic urticaria. It may also be used in patients with concomitant asthma.
Mechanism of Actions
According to DIOne, a medication management system used by hospitals, loratadine is a long-acting, tricyclic antihistamine that selectively inhibits peripheral histamine-1 receptors and is considered a nonsedating antihistamine.
Cetirizine, is a long-acting selective histamine H1-receptor antagonist and is considered a second-generation, low-sedating antihistamine. In addition to competitively inhibiting histamine at peripheral receptor sites, cetirizine has been shown to suppress histamine release during the late phase of allergic reactions.
According to DIOne, cetirizine has been shown to be more sedating than loratadine.
Dosing and Contraindications
Loratadine is available in 5mg and 10mg tablets, orally disintegrating tablets, and syrup.
Cetirizine hydrochloride is available in tablets 5mg or 10mg, chewable tablets of the same strength, and syrup.
Both drugs are contraindicated in patients with renal dysfunction and liver disease.
Reported side effects of loratadine include headache, hypertension, hypotension, palpitation, supraventricular tachyarrhythmias, syncope, tachycardia, nausea, dry mouth, jaundice, hepatitis, and hepatic necrosis.
Reported side effects of cetirizine Hydrochloride include headache, fatigue, somnolence, dizziness, insomnia, nervousness, dry mouth, nausea, vomiting, pharyngitis, dyspepsia, and increased appetite.
Warnings for Loratadine
The only warnings for loratadine reported on DIOne were that it may cause dizziness, somnolence, and fatigue in some patients and that patients taking this drug should wait to see how they react to the medication before they drive or operate heavy machinery.
Warnings for Cetirizine Hydrochloride
According to DIOne, clinical trials showed occurrences of somnolence and therefore caution should be exercised when driving a car or operating potential dangerous machinery.
Drinking alcohol or taking other central nervous system depressants must be avoided because alertness will be further decreased.