Epidural administration (from Ancient Greek ἐπί, "on, upon" + dura mater) is a medical route of administration in which a drug such as epidural analgesia and epidural anesthesia or contrast agent is injected into the epidural space around the spinal cord. The epidural route is frequently employed by certain physicians and nurse anesthetists to administer local anesthetic agents, and occasionally to administer diagnostic (e.g. radio-contrast agents) and therapeutic (e.g., glucocorticoids) chemical substances. Epidural techniques frequently involve injection of drugs through a catheter placed into the epidural space. The injection can result in a loss of sensation—including the sensation of pain—by blocking the transmission of signals through nerve fibres in or near the spinal cord.