None of the required books are mandatory, depending on how well you want to excel in the class.
I'm assuming most of you guys want to do the best.
I would suggest, if you could only afford a couple books, go with the 2 from healthcare. She does test on some of the stuff from the book itself, although it's a couple questions per exam, but sometimes it's the tie-breaker!!
For pharmaceutics, you will most likely need it for the lab portion during spring as well, so might as well.
For physio, seifter is the main book used for physio 2 for your summer semester... i'd suggest you can get that one too.
For biochem, he assigns problems from the book that will be very similar to some of the questions on his exams, and he'll stress to you which problems you really should work on and make sure you know how to do them.
All those books are supplemental, for reference only. Healthcare might be the only one that is really needed. The others are for if you don't understand the material presented in class.
Be aware that the notes from professors are not always in full sentences, so if you miss something, or have a hard time understanding that subject matter, you might want to buy the books. You could always sell them back to the P1s next year