Is Taking Frequent Epidural Injections For Back Pain Safe?

my husband had a stent fitted 6th Jan 2011. He suffers from severe back pain due to a failed back operation 15 years ago, he has epidural injection about every 4 months. His last epidural was september 11 2010. He is due to have an epidual 9th April is this safe and okay. The back pain is affecting his recouperation from the Stent and Pacemaker. I would really apprectiate your advise.