My son has been on hydroxine for a few years. And taking the magnesium glycinate supplement for 2 years and melatonin since he was 4.

Milk and Chicken create a chemical that naturally kicks off the body's need for sleep.
Also;
Depending on the 'Delivery' of Melatonin also matters, IE=:
Tablets = Take up to 45 minutes to start working (Also can cause Night Terrors).
Gummies = Takes 20 to 30 minutes to work. (no Night Terrors).
Liquid = Takes 10 to 20 minutes to work (no Night Terrors).
And again, Also; Timing matters as well as Routine.
[EDIT]
Also a Full Dose is not always necessary, sometimes the body needs just enough to start the reaction.

So, the most common medication for Autistic children for sleep is Clonidine. Widely used for ADHD children with more emphasis on hyperactivity, it calms the child down and slows brain activity so they can fall asleep better. It’s also used to counter anxiety. I was once prescribed Clonidine to help me fall asleep better and it helped me as long as I don’t stare at a phone screen overnight.

First of all, congratulations on potty training! 🎉🎉🎉

We completely understand the sleep deprivation and lack of routine situation. My son is 24 now and he’s been on clonodine for as long as I can remember. The doctor recently added Trazodone. It’s my understanding that many doctors are pulling back on clonodine but even melatonin has its risks. Our kids need their sleep and we certainly deserve it too. Push them to provide something that helps and keep LOTS of documentation on what, and when they do it…(or not.)

So are these medications used for long term?