Ketamine

What is Ketamine?

Ketamine is an agent that has been used as an anaesthetic primarily in emergency, paediatric and general settings for many years.  It has also been used in acute pain and has become now used more commonly for chronic pain conditions and chronic psychiatric conditions.

How does Ketamine Work?

The exact mechanism of Ketamine’s effect on chronic pain is complex and poorly understood.  It is thought to act on a group of receptors, NMDA (N-methyl, M-aspartate receptor), they have to do with the perception of pain, memory, arousal and awareness.  This drug blocks the receptors and has other effects on the structure of the central nervous system that can be long lasting.

What are the side-effects from Ketamine?

Ketamine has a range of side-effects but the most important ones are:

1. feeling of dissociation, a removal from one’s body and person;
2. nausea;
3. palpitations (tachycardia);
4. deranged liver function and, rarely, hallucinations and delusions
5. chemical irritation of the skin and underlying tissue (cellulitis)

While you have this drug, you will be regularly reviewed by a nursing and medical staff and the drug’s affect, monitored and titrated and adjusted as needed.

How is the drug administered?

The drug is administered parenterally.  A subcutaneous infusion is a small tube that is inserted underneath your skin, the drug is infused through a syringe, which is enclosed in a box, over 24 hours.  We usually like the patients to have 7 to 10 days of this drug.

There are some other ways of giving Ketamine, both sublingually (under the tongue) and oral lozenges however, the amount of free drug that is available once it is metabolised by the liver, is quite low.

Are there any other drugs that may be used during this period?

Other drugs may be co-administered with Ketamine and these include Midazolam, Clonidine, Maxolon and Dexamethasone.  These are designed to decrease the adverse effects of the drug. 

What happens while I am on the Ketamine infusion?

We only use Ketamine as an adjunct to rehabilitation and for adjusting of other medications. While you are on this drug, it is expected that you engage in regular physiotherapy and occupational therapy on a daily basis. 

We may also use the effect of the Ketamine to adjust your other medications so that your long term analgesic plan is safe.  This most commonly involves reduction of your opioids (morphine related medication) and  increase in adjuvant medication (anticonvulsants/antidepressants).

It may also be expected that you will be seen by psychiatrist and psychologist as part of the rehabilitation process.

How long can I expect to have an effect from the Ketamine?

This is quite variable but many patients get 3 to 12 months of relief from a Ketamine infusion. Some patients have no improvement or intolerable adverse effects. It is not possible to predict and individual patient response.

Is there anyone who should not have ketamine

You must be assessed by a medical professional prior to been given this drug.

You may be excluded if you have the following medical conditions:

• Pregnancy
• Liver problems
• Some cardiac conditions
• Some Psychiatric conditions

Questions:

If you have any further questions, please discuss this with your medical specialist at your next appointment.