Hi Andrea
I used to take Half Inderal (propananol sp?) it has a calming effect. If you are getting over tired on what you are taking it maybe that the dose is too strong. You need to find some middle ground. It could also be because the ANXIETY has worn you out and when you feel the peace of the medication it is an overwhelming relief and makes you feel tired.
Which ever when you are feeling well it is a good time to work on the underlying problem causing the anxiety. Reading books on anxiety with a view to self help can be useful.
Take care
Lizzy XX