my Kaplan teacher did exactly that. he was a first year dentistry student somewhere in NY (i forget) and decided it was not challenging enough for him. He took the MCAT and was admitted to Oregon Health & Science University. he had an awesome MCAT score which probably proved to the committee that he can do the work (he came from a not too well known state school). he also said he was very frank with his interviewers about his reasons for switching and they could tell that he was not one to quit things too easily. so i think there's hope if you decide to do the same.