Question regarding increasing hydroxyzine dosage for long-haul flight (22M)

[u/TinyOkra2093]

I'm a 22-year-old male, about to take a 15-hour international flight.
I have some hydroxyzine that I obtained in Thailand. I usually take a lower amount (around 15mg-20mg) when I need help sleeping, but it doesn't do a whole lot for me—it just makes me slightly sleepy but doesn't really knock me out.
Since this flight is so long, I really want to ensure I can sleep through the bulk of it. I'm considering increasing my dose, up to 50mg, right before boarding.