4 doctors weighed in:
How long does xyzal (levocetirizine) drowsiness last for?
4 doctors weighed in

Dr. Steven Machtinger
Internal Medicine - Allergy & Immunology
3 doctors agree
In brief: Up to 24 hours
But for most 8 hours.
With continued daily use you should feel less drowsy each day. The problem is that antihistamines that cause sedation also slow reaction times. While the sedative properties diminish with time the effect of reaction time does not. You just may feel as though you are fully alert because you are no longer sleepy. This can increase the risk of accidents.

In brief: Up to 24 hours
But for most 8 hours.
With continued daily use you should feel less drowsy each day. The problem is that antihistamines that cause sedation also slow reaction times. While the sedative properties diminish with time the effect of reaction time does not. You just may feel as though you are fully alert because you are no longer sleepy. This can increase the risk of accidents.
Dr. Steven Machtinger
Dr. Steven Machtinger
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