"Dress for success;" is the motto and your interview attire is important to medical school admissions officers. Whether you like it or not your clothing says a lot about you as an individual and they will leave a lasting impression. With this mentioned, the best idea is to dress formally, conservatively, and appropriately. Trendy and flashy have no place in an interview no matter what the setting.
I know you may be tempted to wear sneakers, but don't, it totally messes up all the work of the professional image that you are attempting to convey. Therefore, wear a pair of dress shoes either in black or dark brown.
Guys, I am a hat man myself but it is not appropriate interview attire to have anything covering your head unless for religious/ethnic purposes. Please do not wear any unwarranted accessories i.e. chains, earrings, bracelets. These can all be worn at a later time.
Ladies and gentleman, I know perfume and cologne serves a purpose but having your interviewer suffocate over your scent is a bad idea. One to two spays will suffice and anything more is too much. Fragances are to be scented in close proximity and should not announce your arrival.
In general use your best judgement and remember you will be interviewing with medical school representatives. Be clean, well groomed, and free of body odor. Also chewing gum is absolutely prohibited, just don't do it! Let your mind, intellect, and personality make the lasting impression not superficial articles of clothing.