(EDIT: Thanks for the comments - I'm working on improving references - apologies)
In patients with Borderline personality disorder or treatment resistant depression have what must be among the highest rates of suicide in mental health, excluding comorbidities. I will focus on BPD to simplify the question. Up to 10% are expected to have killed themselves, the study shows. (Treatment is often ineffective compared to other diseases with suicidal ideation).
Some long term medications are used in Asperger's to quell the overwhelming sensory percepts and the irritability, impulses and distress that transpires, leading to dangerous behaviours. Ie, the ASD patient's stress rises disproportionately due to oversensitivities, and partially developed coping mechanisms heighten risk of suicide. (References needed. Lots).
Long acting benzodiazepines are used to treat acute symptoms especially involving anxiety (stress). But I don't know why I can't find information on why medications such as Pregabalin are not cited as a long term treatment for persistent suicidal ideation but for anxiety.
I believe Pregabalin is offered on top of mood stabilizers for BPD patients to take the edge off self-destructive behaviours. The risk is Pregabalin itself has a high risk of causing suicidality. But this would be ignored until it occurs since obviously it would have been assessed as a probably benefit. (References needed - this might answer my question!)
But perhaps there are other meds with sedating action approved for long term use, used to treat suicidality?