Are there different types of ketamine?

ketamine infusions

ketamine infusions

Two main types of ketamine are used to treat major depression that hasn’t responded to two or more medications (treatment-resistant depression).

  • Racemic ketamine, which is most often given as an infusion into the bloodstream. This is sometimes called intravenous, or IV, ketamine. It is a mixture of two mirror-image molecules: “R” and “S” ketamine. While it was approved decades ago as an anesthetic by the FDA, it is used off-label to treat depression.
  • Esketamine (Spravato), which the FDA approved in March, is given as a nasal spray. It uses only the “S” molecule.

ketamine infusions

Thus far, most research has been on ketamine infusions.

The two forms of ketamine interact differently with receptors in the brain. The delivery of ketamine and the type given affect drug effectiveness and side effects. We don’t yet know which type is more effective or how much side effects may differ. Further research comparing effectiveness and side effects is needed.

Ketamine drug ranks among the most basic pharmacologic tools of the anesthesiologist. Approved in 1970 as an anesthetic agent derived from phencyclidine, the drug quickly proved its worth in battlefield settings where maintenance of hemodynamic stability was a prime requirement.1  To this day the drug is valued for use in unstable patients, in those with reactive airway disease, and in situations where sedation, analgesia, or induction is required without having intravenous access. Those indications alone provide ketamine a prominent and durable position in our pharmacologic armamentarium. However, after decades of use, and illicit abuse for its ability to provide a dissociative high, the drug may still have a few tricks to reveal, including the treatment of psychologic disorders, the prevention of chronic postoperative pain, and, as addressed by Pickering et al.2  in this issue of Anesthesiology, the treatment of chronic pain when infused at low doses.

What are the possible side effects of ketamine?

All drugs have side effects. When someone is suicidal or severely depressed, possible benefits may outweigh possible risks.

Ketamine given by infusion may cause:

  • high blood pressure
  • nausea and vomiting
  • perceptual disturbances (time appearing to speed up or slow down; colors, textures, and noises that seem especially stimulating; blurry vision)
  • dissociation (sometimes called out-of-body experiences); rarely, a person may feel as if they are looking down on their body, for example.

Generally, any changes in perception or dissociation are most noticeable during the first infusion and end very quickly afterward.

Esketamine nasal spray may cause the same side effects. However, the timing and intensity of those effects is different.

Long-term or frequent use of ketamine may have additional side effects. More research on this is needed.

ketamine infusions

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