you can apply to medical school after or during ANY undergraduate degree- so yes Med Rad is fine- pretty much every school also has a statement that they do not discriminate based on what program you are in
as for course requirements that depends on where you want to go.
For canadian uni's it varies so to find specific course requirements you have to check them out separately: http://www.ouac.on.ca/omsas/omsas-schools/
for the states i believe you need to have 2 orgo (which means you need to have the first year chems as well), 2 english, 2 physics and im not sure how many bio (as i am in bio and have never bothered to look
hope that helps- but again it all depends on the school