I would contact both schools to see if there will be coursework that will allow you to concentrate on that specific area of study. I will be matriculating at UIC for epi this year, but I have not seen very much focus on pharmaceuticals within the degree (there are some pharmaceutical-focused PhD programs, so you could look to see if they'd let you take courses outside of the degree?). If BU has a concentration in that, it seems like it would be the better option for you. However, as
@backwardinduction said, there has been talk of them removing concentrations altogether. You may want to contact them to make sure that you'll still be able to focus on that after all of their (major) changes have been made.