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Medication for Pain Series: Ketamine

May 19th, 2014 · No Comments

This article is in our series on Medications for Pain. What are your choices? How do various medications work? What are the pros and cons? Side effects?

The medication Ketamine is an anesthetic. Anesthetics are drugs which prevent sensations, particularly pain. Ketamine is an NMDA-receptor antagonist. Also in this class is Dextromethorophan (which is an active ingredient in cough syrup). These medications can be used:

  • Topically (through the skin)
  • By mouth in pill form
  • Intravenous (IV) low-dose or moderate-dose infusion
  • Intravenous (IV) at high doses (“ketamine coma”)

One study showed that moderate-dose infusions give much better pain relief than low-dose infusions do, without additional side effects, and so moderate-dosages are now recommended.

Effect of Ketamine:
Ketamine and others in this class are called NMDA-receptor antagonists. This means they block nerve conduction at a specific (NMDA) neurotransmitter site.

Uses of Ketamine:
Ketamine is only approved as an anesthetic for surgical procedures, not for chronic pain. In chronic pain treatment, it’s used on the skin for nerve pain, and by IV for CRPS (Complex Regional Pain Syndrome or RSD). Dextromethorophan, when used for chronic pain, is given in concentrated pill form, as the amount in cough syrup is very low.

Side Effects:
Ketamine’s short term side-effects include anxiety and hallucinations. There’s been concern over unknown longer-term consequences, including cognitive (memory) problems. However, one study showed no decrease in attention, learning, and memory in 9 patients with CRPS who underwent a Ketamine coma. Although we’re still at an early stage in learning how to use Ketamine more safely for chronic pain, I’m becoming a bigger fan of this treatment for use after other treatments have not been effective.

Also Interesting:
Ketamine’s other uses include in veterinary medicine, battlefield medicine, and as a recreational drug.

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