I think it all depends on what you plan to do during your gap year. If you can use the year to work full time in a research lab or pharmacy, both of those would be good uses of your time, would help you prepare for the profession and be a good addition to your application. However, once you take a break from school, it can be very difficult to go back, so make sure you have a plan laid out for going back to school. You also need to be aware that the further removed from school you are, the more difficult it will be to obtain letters of recommendation from your professors. Ask them now, and make sure you keep in contact with them over the next year or so. Finally, some schools have time-limits on science coursework, and you may find yourself needing to repeat classes that are older than 5 years.