What Causes Swelling In The Hand And Finger After Taking Lithium Carbonate?

I m making this request for a friend. She s 81. She takes a statin, and thyroxin for a sluggish thyroid. Lithium carbonate for bipolar disorder. The back of hands have swelling between wrist bone and 2nd finger bones with a generalized swelling between the fingers. Right hand worse than left. Feet are also swollen around the ankle area. Her doctor has proscribed Prolea but since she had jaw pain with Fosamax at least 10 years ago, she s reluctant to take another bone building medication. She wants to know what is causing this swelling on the backs of my hands and now my feet. Her physician is on vacation so that s why we d try this and see if there s something going on that she should go to the hospital for, or at least try and get in to see another practioner before her PC gets back....thank you...