As it is, the difference between HPD, BPD and NPD is, to my mind, rather blurred in the extreme cases. The Narcissist must learn that his past experiences are NOT laws of nature, that not all adults are abusive, that relationships can be nurturing and supportive. But the narcissist devalues the therapist. And this is only in the first three sessions of the therapy. This abusive internal dialogue becomes more vituperative and pejorative as therapy progresses.
Narcissists generally are averse to medication.
Resorting to medicines is an implied admission that something is wrong. Narcissists are control freaks and afraid to lose control. Narcissists MUST dramatize their lives to feel worthy and special. Narcissists are drama queens. Very much like in the physical world, change is brought about only through the incredible powers of torsion and breakage.