It depends on the chemistry in question. Within the phenethylamines alone there are dozens of mood-altering drugs, all with differing effects on the affect.
Consider too that some amides and indole ring entheogens have the possibility of suspending in total that thing we call "personality," for indeed, there is no individuated self remaining when under their inluence. In these cases it might be more useful to consider transpersonal psychology and the shamanic/esoteric rituals born of perennial wisdom traditions and gnostic pursuits as means by which we may understand.
I like that question, it's interesting. I'm inclined to say no. The phenotype of your personality may change and getting rid of physical barriers that stunt your growth may help you develop other functions. However, I think the preferences are still hardwired into your system (and by functions, I mean Si, Ne, Fi, etc.), independent of phenotypes.
So, for example, if you have social anxiety, and appear shy, then take anti-social anxiety pills (too lazy to look 'em up), you will appear to have morphed from introvert to extrovert. At the same time, you were and still are dominated by extraverted perception (primary function Se or Ne). This would mean that you are and always were an extravert (according to the MBTI system), regardless of how outgoing you appear.
Now, when it comes to conditions like schizophrenia, where the actual brain is messed up beyond "chemical imbalances," I'm not sure. I'm also going to acknowledge that I have no rational argument behind the "hard-wired" theory beyond what I see in chemically healthy persons (which includes the emotionaly unhealthy). Hmmmm, I guess I'm saying it's genetic.
I'm not sure of the validity of nicotine as a mood altering drug but it has and does help me to deal with large forums of people (you know like groups of more than say two). I've noticed that in depth discussion, especially about important things, will drive me to smoke more. I associate it with taking the edge off my nerves which then allows me to focus despite being tense.
Oh yeah, caffeine is another one. A drug (to be course in my naming) which helps to keep the energy going... another tool for dealing with people. Once relaxed and full of energy, it's easier to meet and greet..