I have known people finding some anti-psychotics helpful for agitation and self-harm or impulsivity. Some take anti-depressants as well since there is that component though it is not officially part of the diagnosis, but BPD often has its roots in trauma and loss so it seems appropriate. I do not buy that BPD is so bad that it is resistant to treatment. There are people who wanted to rename BPD as "emotional dysregulation disorder" because that is the core feature. Anything that helps regulate emotions then would be helpful.