Two weeks after the initial procedure, an identical procedure to the first one will be done by the same physician or his designate. In addition to the study medication, each patient in each group will receive 0.5 ml of 0.5% bupivacaine local anesthetic for immediate pain relief during both injections before the study drug is delivered. The efficacy of blinding will be assessed by a disinterested observer unaware of the randomization results after the second procedure before discharge. Follow-up visits will be conducted one, three and six months after the second injection, for those subjects who continue to experience > 50% pain relief.