Trazodone has low rates of side effects with low doses used PRN for sleep.
Olanzapine and Quetiapine 2nd gen antipsychotics used for sleep and delirium. Avoid in older patients with dementia (black box warning).

Melatonin

MOA: chronohypnotic that decreases firing rate of neurons in SCN via MT1 receptor, but only when endogenous levels are low (daytime)
In older adults, the amount of melatonin synthesized and the number and affinity of MT1 receptors all decrease.
Higher doses might increase total sleep time.
Does not make you feel drowsy. It enhances natural sleep wake cycle. Must be paired with good sleep hygiene. Only need very small amounts (1 mg). Give 1 hr before bedtime.
The body makes 1 mg per day, at higher doses exogenous melatonin might decrease your body's ability to synthesize it on its own.
Higher doses in the short term show a dose dependent effect, but this wears off quickly and then melatonin stops working at all.
Refs: 15649737, 11600532, 24802882, 35436355, 33417003

Insomnia