Ketamine

In this post I am going to be talking about ketamine, a non-opioid pain medication that can be helpful in acute and chronic pain. I’ll first go over the pharmacology of this medication and explain why it is different from opioids, which can be useful in patients whose bodies are very used to opioid medications. I’ll also discuss some common uses for acute and chronic pain and briefly touch on a new intranasal formulation which is currently only approved for depression.

Ketamine is known as a dissociative anesthetic medication, which means that in high doses it causes patients to be almost in a trance-like state where painful stimuli do not cause distress. It blocks a receptor known as the NMDA receptor, and so its mechanism of action is totally different than opioids, which work on opioid receptors.

This property can be used to benefit patients who are chronically on opioids, because over time, people who take opioids on a regular basis become tolerant, which means that the same doses no longer affect them in the same way. Using a pain medication that affects a different receptor is like a breath of fresh air to the system, and can provide powerful pain relief.

In the acute pain/anesthesia setting, ketamine is a really helpful adjunct to reduce the amount of opioids required. People have different ways of adding ketamine to an anesthetic, but typically a larger dose is given at the start of a procedure, and then a lower dose is run as an infusion during the case. This is probably not necessary for a minor procedure in someone who never uses opioids, but in a large painful surgery, especially in someone who is already tolerant, using ketamine can be a godsend for intraoperative and postoperative pain relief. There is also a huge role for ketamine in patients with severe burns who require frequent dressing changes and procedures on the damaged skin.

The use of ketamine for chronic pain is slightly more controversial. Because in high doses ketamine can cause hallucinations/confusion, it isn’t really practical to send someone home with ketamine for regular use. The one exception is the use of topical ketamine, which can be helpful in patients with conditions like complex regional pain syndrome.

It is more common to either admit patients for several days of low dose ketamine infusions, or to do this as an outpatient. In addition to the big time commitment for patients, this can be very costly, as ketamine infusions for chronic pain are not covered by insurance. However, in patients with chronic pain who have exhausted many other options, a ketamine treatment can be incredibly helpful in helping to “reset” the pain pathways and to turn down the volume on chronic pain.

This is slightly out of my area, but since ketamine is getting so much attention from a new intranasal medication that hit the market recently, I’ll mention briefly that ketamine has also been noted to help patients with depression. Anecdotally, when I was in training, we would have patients who had been given ketamine as part of their anesthetic and found it helped their mood after. Esketamine is a nasal spray formulation of ketamine that has recently been approved for depression. It will be interesting to see if eventually the labelling will be expand to include chronic pain purposes, or if other similar medications will be developed for pain.

It is important to note that there is potential for abuse and misuse of ketamine, although many people dislike the feeling of being high on ketamine due to the hallucinations. This is less of a concern if it is used in the ways I discussed earlier.

If you are wondering if ketamine might help with your chronic pain or be a helpful adjuvant for an upcoming surgery, you should discuss with a pain management doctor or anesthesiologist in person! And don’t forget to subscribe to my blog here so you never miss a post.