Hi,
My wife has been on Nexavar for almost 10 months but she doesn't get the back pain. However, you should consult your doctor to perscribe a pain relieve meds cause there are so many and each person may require different type of pain killers. Have your husband get an examination to identify the cause of this pain? It's better to know exactly what's causing this pain so your doctor might be able to recommend other specific & additional treatement.
Best,
Petch