You'll basically find the following types of medical school:
1. Those that want 60-90 credits completed in the U.S. with those credits to include chemistry, biology, physics, organic chemistry, and sometimes English. These schools are most common. Sometimes completion of the prerequisite courses alone with satisfy the Admissions Committee and they'll let you slide if you have a M.S. or a Ph.D. (with a decent GPA) from the U.S.
2. Those that want an entire U.S. undergraduate degree earned from scratch (Mayo Clinic springs to mind). These schools are uncommon.
3. Those that want 60-90 credits completed in the U.S., and the credits can be a mix of graduate school credits and one or two scattered prerequisites. If you look hard enough, you'll find a handful of these schools. This is the route that I took, but keep in mind that no two applicants look the same and so conditions will vary.
4. Those that want 60-90 credits completed in the U.S. and they won't make you do the prerequisites over. These medical schools are VERY hard to find, and usually a political connection at the school makes this possible.
If you want to bypass studying for a U.S. undergraduate degree, some colleges will allow you to roll several years of foreign undergraduate credits on a 'pass' basis into a an accelerated U.S. undergraduate degree, and you may only get away with taking the prerequisites over 18 months. Find BlueMirage on SDN. This is what he did, and he successfully gained admission, too.
In all of the above cases, a professional evaluated transcript of the foreign credits will generally be expected. AMCAS will not verify those grades, but several medical schools will add them to your file.
All of the above information also assumes that the applicant has a green card or U.S. citizenship; without that, the level of difficulty in securing admission for each of the above cases should be multiplied several fold.
A U.S. Ph.D. - even with a nice GPA - does not carry a whole lot of clout with U.S. medical schools. This is from first-hand experience. Neither do prerequisite courses earned overseas - even if it's from a 'prestigious' school. This is also from first-hand experience. Publications do help for some of the private, research-oriented medical schools but, again, you really have to look as close to a U.S. applicant as possible. PM me if you have any other worries. I've posted a lot on this subject and I don't want to start sounding like a broken record. Good luck!
