After an injection, lidocaine's effects last an hour or two. Bupivacaine is long-acting, with effects lasting from two to four hours or more. Several factors affect how long these medicines work.

Four hundred patients were randomly assigned to either a standard ESI (glucocorticoids) with lidocaine, or an injection of lidocaine alone, with potential for a repeat study injection at 3 weeks.

but since lidocaine alone is not thought to have lasting effects (e.g., weeks), the authors felt that this was a suitable placebo. The failure to demonstrate efficacy of epidural steroid ...