Cetirizine
- Class: Second-generation antihistamine
- Used for: allergies
- Say it: seh-TEER-ih-zeen
- Forms: tablet, chewable tablet, oral liquid
Remember the name – CETI → settee, the sofa
CETIRIZINE can still land you on the SETTEE — it is the sleepiest of the modern antihistamines.
It crosses into the brain a little more than loratadine or fexofenadine, and sedates roughly one person in ten. For someone who drives for a living, choose another.
CETIRIZINE can still land you on the SETTEE — it is the sleepiest of the modern antihistamines.
It crosses into the brain a little more than loratadine or fexofenadine, and sedates roughly one person in ten. For someone who drives for a living, choose another.
Mnemonic: Second generation stays out of the brain
Cetirizine blocks the same H1 receptor as diphenhydramine but barely crosses the blood-brain barrier, so it treats the allergy without the sedation. Of the second-generation drugs it is the most likely to cause some drowsiness.
Cetirizine blocks the same H1 receptor as diphenhydramine but barely crosses the blood-brain barrier, so it treats the allergy without the sedation. Of the second-generation drugs it is the most likely to cause some drowsiness.
Side effects
Common: drowsiness, dry mouth, fatigue
Serious:
Typical dose
10 mg once daily
5 mg is a reasonable starting dose if drowsiness matters. Halve it in renal impairment.
Check yourself
Why does cetirizine cause less sedation than diphenhydramine?
- It crosses the blood-brain barrier poorly, so it reaches few central H1 receptors
- It blocks a completely different receptor
- It is taken at a much lower dose
- It is broken down before it reaches the blood
Show answer
A. It crosses the blood-brain barrier poorly, so it reaches few central H1 receptors
Both block H1. Sedation comes from blocking H1 in the brain, and the second-generation drugs are designed not to get there. Cetirizine crosses a little more than loratadine does, which is why it is the drowsiest of the modern ones.
See it, don't memorize it
The app has the mechanism comic and a patient case for Cetirizine – plus the name link, the class mnemonic, pronunciation you can hear, and a self-check, for the top 100 drugs. One purchase, no subscription, no account.