Focus on doing well on your core classes and the pre-requisite courses required for admissions, especially the math and science courses.
On a side note, if you aren't doing well in the core classes, ask yourself if you really want to be studying pharmaceutical sciences for another 4 years?
But if you have a legitimate reason for your grades being less than stellar, use your personal statement as an opportunity to explain why your grades aren't an adequate representation of your potential. For example, if you were working two jobs to support a family, include that in your essay and emphasize how this life experience will make you a better student in the future and better pharmacist (eg, learning the importance of time management, ways to stay focused, how to prioritize life goals, and multitask, etc.).
Best of luck to you! Hope this helps! :)