After the catheter is in place, a combination of narcotic and anesthesia is administered either by a pump or by periodic injections into the epidural space. A narcotic such as fentanyl or morphine is given to replace some of the higher doses of anesthetic, like bupivacaine, chloroprocaine, or lidocaine.
http://americanpregnancy.org/labor-and-birth/epidural/
For example, if the injection is given in your lumbar spine, the medication will usually affect the entire lower portion of your spine. Epidural injections are used to treat radicular pain caused by nerve irritation. This type of pain is usually caused by herniated discs or spinal stenosis. A herniated disc occurs when pressure or degeneration produces a tear in the disc's outer ring (the annulus), and the nucleus ruptures out of its normal space.
https://www.depuysynthes.com/patients/aabp/researchingtreatmentrecovery/spinalinjections
1 The caudal injection is the least complicated way to access the epidural space; however, it is not as localized or confined an injection as the transforminal approach.  The translaminar injection delivers the medication directly into the epidural space and therefore closer to the source of pain. However, the medication is not guaranteed to flow to the front epidural space, the area where the irritated nerve can be found.
https://www.hss.edu/conditions_epidural-injections-faqs.asp
Intravenous (IV) fluids will be started before active labor begins and prior to the procedure of placing the epidural. You can expect to receive 1-2 liters of IV fluids throughout labor and delivery. An anesthesiologist (specialist in administering anesthesia), an obstetrician, or nurse-anesthetist will administer your epidural.
http://americanpregnancy.org/labor-and-birth/epidural/
It may be necessary to have several epidural injections in a series over a period of a few weeks. This is because the relief from the epidural injection usually decreases with time. It is not uncommon to have three lumbar epidural injections, each about ten days apart.
https://www.depuysynthes.com/patients/aabp/researchingtreatmentrecovery/spinalinjections
This epidural space is the space between the dural sac - which surrounds the spinal cord and exiting spinal nerves - and the boney spinal column. This is the space into which disc material can potentially herniate (jut out unnaturally) and cause pressure and inflammation around spinal nerves.
https://www.hss.edu/conditions_epidural-injections-faqs.asp
Generally, patients come in about one hour prior to the procedure. Some patients require blood work to rule out an infection or bleeding risks. Patients usually can eat a light meal 4 hours prior to the procedure, and they can resume their normal eating habits after the procedure.
https://www.hss.edu/conditions_epidural-injections-faqs.asp
Using Epidural Anesthesia During Labor: Benefits and Risks. Epidural anesthesia is the most popular method of pain relief during labor. Women request an epidural by name more than any other method of pain relief. More than 50% of women giving birth at hospitals use epidural anesthesia. As you prepare yourself for “labor day,” try to learn as much as possible about pain relief options so that you will be better prepared to make decisions during the labor and birth process.
http://americanpregnancy.org/labor-and-birth/epidural/
An ESI is a common type of injection that is given to provide relief from certain types of low back and neck pain. The epidural space is the space between the covering of your spinal cord (dura mater) and the inside of the bony spinal canal. It runs the entire length of your spine.
https://www.depuysynthes.com/patients/aabp/researchingtreatmentrecovery/spinalinjections
There are a few contraindications to performing lumbosacral epidural steroid injections, including bleeding disorder, anticoagulation, and allergy to medications. Other contraindications include pregnancy and the inability to be positioned horizontally or to “lie prone”.
https://www.hss.edu/conditions_epidural-injections-faqs.asp
how soon together for epidural injections
Epidural injections are together for few weeks. An epidural injection together after a few weeks.