If the course is not a prereq, drop it if you're not yet past the deadline for withdrawing. Verify w/ pharmacy school first, of course, but they shouldn't care if it was never a required course.
They won't take action unless it is a pre-req or if they have rules regarding all courses. You don't have much to worry about but you should withdraw if you can. If they tell you its past the deadline to withdraw, you can ask for an appeal from board of your school and they will most likely let you withdraw given the reasons you aren't do well.