Cosco and Sams having a biding war on cetirizine (where 300 pills cost $10 to $15), you've probably seen patients in your office who are experimenting with dosages on their own. We are used to pushing antihistamines to tolerance with urticaria. Can we extrapolate that to rhinitis? If one 10-mg cetrazine is good, are two or three better for nasal allergy that doesn't seem to respond?
Cetirizine studies have clearly identified that there is a dose response problem with sedation. Sedation includes both somnolence and CNS impairment. Even 10 mg/day is associated with sedation greater than placebo. You know there are no reliable data to suggest that 20 or 30 mg/day of cetirizine will provide greater relief of nasal allergies than 10 mg/day.
High-dose antihistamines have their role in chronic urticaria however: High-dose desloratadine (4-times the standard dose) is effective and safe in cold urticaria.
ACAAI News Archive, 02/2010.