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Side effects

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Ketamine is known to produce some side-effects. It is not a licensed treatment for depression and the effects of taking it long term are unknown. There may also be unusual side-effects which occur acutely which are unreported.

Ketamine commonly causes brief side effects. These are more common at higher doses, but the relationship between dose and side-effects is variable, even within the same patient.

Brief side effects

Side-effects which occur during or shortly after treatment include:

Feeling dissociated (mind and body feel separate). Occasionally, this extends to the point of an ‘out of body’ experience.


Feeling ‘a bit drunk’.

A floating sensation.



Sedation and sleepiness. Fatigue is also common in the hours after the infusion.

Altered perception– things “look peculiar” or sound different.

Nausea or vomiting – this can be treated with antinausea agents. Do not have a big meal before treatment.

Anxiety – this can extend to the point of panic. It may be associated with a ‘near death’ experience. This can occur ‘out of blue’ even in people who have had many treatments. The anxiety diminishes rapidly as the drug is broken down in the body, so the infusion can be turned off if necessary. In this case, the anxiety settles within 5-10 minutes.

Headache – responds to paracetamol.

Temporary bruising. The treatment involves a needle being put into the vein on the back of your hand and a low dose of ketamine infused over 40 minutes.

An increase in blood pressure or a fast heart rate. This will be monitored during you first infusion and before and after subsequent infusions During the infusion, if you find the side effects too unpleasant then please tell a member of the team that you would like to stop.

Less-common side effects

Vivid dreams.

Hallucinations (feeling, seeing or hearing something that is not actually there).

Dysphoria (feeling unwell or unhappy) Occasionally people have felt a worsening in their depressive symptoms and suicidality whilst taking ketamine. If this happens, you should notify the ketamine clinic and your local team.

These side effects wear off within one hour. However, patients commonly feel tired for the rest of the day after treatment.

Mania (unusually elevated mood which causes problems). Ketamine should be stopped immediately if you suspect this is happening. The ketamine team and your local team need to be informed promptly.

Rare physical side-effects

Liver damage. If you are receiving ongoing ketamine treatment, you will need a monitoring blood test every 6-8 months. This should be done by your GP. Alternatively, we can do this when you attend to pickup medication or for an appointment, but you will be charged for this at a rate of £100 per occasion, so we strongly encourage you to have this test done by your GP.

Long term theoretical risks

Dependence.  Ketamine is sometimes taken illegally in large, frequent doses. Drug abusers can become addicted to it. Sometimes people find that if they stop ketamine their depression relapses. This is not the same as addiction. This is reliance.

Sometimes patients taking it for depression find that their depression is no longer controlled despite continuing to have treatment with ketamine. There can be several possible reasons, one of which is that they have developed tolerance to ketamine. This may mean that a treatment break is needed or that it is no longer an effective treatment and therefore will be stopped. Sometimes, the dose can be safely increased. However, it is best to reduce the dose or extend the interval between doses to help maintain the effect.

Sometimes, people find that they think a lot about ketamine and crave it. It is important to notice that this is happening and to be open and honest with the clinical team about this.

We are not aware of reports of anyone who has taken ketamine as prescribed for the treatment of depression and who has become addicted. However, when people use ketamine illegally it is not uncommon for the dose and frequency to escalate.

For comparison, ketamine is much less addictive and dangerous than strong opiates (eg fentanyl, methadone), is probably less addictive and dangerous than tobacco, and has equivalent risks to alcohol and benzodiazepines.

Bladder damage. This is common in people who take illegal ketamine recreationally at doses of over 1g ketamine daily. This dose is substantially higher than the maximum we use.

Drinking plenty and avoiding alcohol reduces the concentration and damage potential of ketamine metabolites in the bladder. The main symptoms of ketamine-induced bladder damage are pain passing water, and needing to pass urine more often. If you start to experience these symptoms please contact your GP and the ketamine clinic.

Cognitive impairment. This has not been observed over 1 year treatment with esketamine, but has been seen in addicts taken high doses daily. It is associated with evidence of brain shrinking and other brain lesions.

Personality change. Apathy has been reported in addicts.

Last updated: 29 October, 2018