I get mine by prescription, so it would not affect me. But, I can see how making it a "behind the counter" drug would make it a hassle (limiting the amount, having to register your ID, and sign for it).
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .