Posted 1/4/2022 9:46 AM (GMT -5)
Hi JMF 🙂
The max "official" dosage is 10 mg (according to rxlist): "one 10 mg capsule once daily; do not take more than one 10 mg capsule in 24 hours. A 5 mg product may be appropriate for less severe symptoms."
I looked into it and the problem with higher dosages is that it starts to cross the blood brain barrier more:
"Second generation antihistamines such as cetirizine are thought to be generally well tolerated with minimal sedation as they cross the blood-brain barrier to a lesser extent compared to first generation antihistamines. However, this crossing is not insignificant. In one adult study, a dose of 20 mg cetirizine was shown to occupy 17–40% of the H1 receptors in the brain depending on receptor location, suggesting that at high doses, cetirizine crosses the blood-brain barrier and may lead to more psychoactive effects."
That said, I'm sure there are people that might be have been fine on it, so it really is a tough decision.