It should be plenty of time to learn those topics.
Assuming pharm covers general principles and ANS pharmacology, one week should be enough to learn that (especially if you don't have to go to class). Obviously, you cannot learn everything written in big Katzung's in that time but assuming your school does not go into THAT much detail, you should be fine.
As for general path, 3 weeks is also more than enough. Again, unless they are expecting you to memorise every piece of information in big Robbins (which I doubt), you can do just fine. A lot of it will be familiar from other courses (molecular biology, immunology) as well.
Overall, I don't think it should be a problem.