Ketamine is a pain reliever analgesic



Having ketamine injected into a vein during surgery will reduce pain, nausea, and vomiting, as well as the use of opioids (morphine-like pain relievers) after surgery.


Inadequate pain management after surgery increases the risk of complications, decreases quality of life and increases the risk of chronic pain. Pain relievers such as acetaminophen and non-steroidal anti-inflammatory drugs (ibuprofen, diclofenac) alone may not be enough. Opioids (strong pain relievers) often cause side effects. Studies suggest that injecting ketamine during surgery can help relieve pain afterwards.

Study characteristics

In July 2018, we looked for randomized clinical trials in which ketamine was injected before, during, or after surgery in adults who had a procedure under general anesthesia. Important endpoints were opioid use and pain at 24 and 48 hours after surgery, time to first demand for pain relievers, and side effects associated with ketamine. We found 130 suitable studies with 8341 participants.

Main results

Compared to participants on the control treatment, patients who received intravenous ketamine took less opioid pain relievers (by about 1-tenth) and had less pain (by about 2-tenths; quality of evidence: moderate or high). Ketamine may be more effective in surgery that is likely to cause more pain. Patients who had received ketamine asked about pain medication 54 minutes later than patients who had not received ketamine (quality of evidence: moderate). Ketamine reduced the risk of postoperative nausea and vomiting by a small proportion (quality of evidence: high). Ketamine was not associated with an increased risk of side effects in the central nervous system (hallucinations, nightmares, or double vision) (quality of evidence: high).

Future research should assess the effects of ketamine after operations that involve severe pain, such as thoracotomies (surgical opening of the chest cavity), back operations or amputations. In addition, an assessment of the effect of ketamine in certain patient groups, e.g. B. the elderly or those with a history of substance abuse, are of interest.

Quality of the evidence

We rated the quality of the evidence from these studies using four categories: very low, low, moderate, or high. Very low quality evidence means that we are very uncertain about the results. High quality evidence means that we have great confidence in the results.

We found the quality of the evidence to be moderate for most outcomes. Many of the studies were small; that was the main reason for downgrading the quality of evidence from “high” to “moderate”. We checked the results by type of surgery, time of ketamine injection, and in larger studies and in patients with more severe pain: the results were consistent and convincing. The evidence was sufficient to allow conclusions to be drawn about the effects of ketamine on pain, pain reliever consumption, and postoperative side effects.