I aimed at doing my prereq's for just one- USC. I applied to 3, USC, UCSD, and Western and thankfully they were all pretty close (except Western was the only one that wanted Anatomy, and USC wanted Interpersonal Communication compared to Speech which UCSD/Western wanted). So it was fairly easy (took me 4 1/3 years
), since USC wants so many prereq's it took care of pretty much everything else. It's pretty challenging trying to squeeze in all the prereq's for different schools. I'll remind you that you better finish all of your Western prereq's by the Spring before you enter pharmacy school because they wont accept summer classes right before entering their pharm school.... which sucks because it'd be nice to be able to save a prereq or 2 to do once you know you're admitted to the school, so it's not like a waste.
I honestly have no idea how you would do USC's prereq's while being an Econ major. You may as well double major or minor in biological sciences too because you need physiology/microbiology/cell bio/biochemistry/molecular biology. It kinda depends what year you are in school, how much work you wanna do. If you're not really serious about going to USC you may not want to do all those prereq's. I'm not sure what Loma Linda's are like, but UCSF and UCSD's prereq's are both fairly extensive too.
Since you wanna go to Western so bad maybe you should just put all your energy into their prereq's and hopefully you'll get in.