I was on it 50mg for anxiety/PTSD and sleep from 2021. It’s a potent antihistamine and its sedative actions are strong. When I first started taking it, I’d fall answer sitting up within the hour. But I got used to it pretty quickly, I’d take it around 2 hours before bedtime.
It did help my anxiety a bit in the evenings - at 50mg, its main mechanism of action is on histamine and a2 adrenaline, both of which have a calming effect.
The downsides - weight gain and becoming dependent on it for sleep. Also it didn’t really help my anxiety in the day. The instant release half life is 6 hours, so mostly out your system by the morning. My psych tried prescribing 25mg for the day but I just couldn’t function on it as I was too tired.
I’m titrating off it now (I’ve successfully treated my anxiety/ptsd with EMDR - highly recommend) and I’m down to 12.5mg. It’s been slow going as the insomnia is mad. You really do become dependent on it for sleep. All the weight has come back off too. On the subject of weight gain, some of it you can’t help, but you do get something called “the quetiapine munchies”, when it kicks in, you just want to eat everything in sight. 😭
If you don’t need it for sleep, and it’s just anxiety, I’d go for a Beta Blocker instead. Propranolol is magic.
Having said all that, everyone is different and this is just my experience with it.
Happy to answer any more questions you might have!