How Long Does Ketamine Last for Depression?

While extremely effective in treating depression, for most, each Ketamine IV infusion only lasts a week or so at most.

The drug ketamine, previously used only as a general anesthetic, is currently being used to treat depression in bipolar disorder and major depressive disorder. While ketamine works quickly (within hours), many patients are concerned about how long the positive effects of Ketamine last; especially given the cost of ketamine infusions ($400-800 per IV treatment here in the U.S.). While there is not enough study done to answer this question definitively, and it does vary from person to person, some things are known.

How Long Does Ketamine Take to Kick In?

The effects of ketamine are typically very fast. It takes about two hours for ketamine’s antidepressant effects to kick in for some people and one study showed that at 24 hours, 71% of patients responded to a single dose of ketamine.

Studies estimate that ketamine is not effective for between 20% and 40% of patients with depression. Those numbers are consistent across major depressive disorder and depression in bipolar disorder.

How Long Does Ketamine Last For?

Most studies have looked at how long the antidepressant effects of ketamine last after a single intravenous (IV) infusion. With only one treatment, people tend to relapse within several days to a week although it can be variable. If a person is to respond positively to ketamine infusions, he or she will typically know within four hours. One study showed that 94% of people who responded positively to ketamine did so by the four-hour mark.

Limited research has been done on ketamine’s effects after a course of multiple treatments. One study in 2012 of 24 patients with treatment-resistant major depressive disorder showed that, after a course of up to six ketamine infusions, the average time to relapse was 18 days. Of the 17 patients in the study who positively responded to ketamine, four remained relapse-free at day 83 (the length of the study). A small number of positive-responders were given venlafaxine extended-release (Effexor ER) in the follow-up period but no change in time-to-relapse was seen.

Long-Term Ketamine Treatment for Depression

No long-term ketamine treatment for depression studies have been done and long-term use of ketamine is not advised. According to guidance given to physicians regarding ketamine depression treatment in 2017:

“. . . ketamine [should] be discontinued if dosing cannot be tapered to a minimum of one dose per week by the second month of treatment, the goal being to eventually discontinue treatment altogether.”

What is known of recreational ketamine use creates cause for concern. Firstly, ketamine is the number one drug of abuse in Asia and so it is considered to have a high abuse potential and a potential for addiction (Can You Get Addicted to Ketamine?). It is for this reason that those with a history of substance abuse are less likely to be candidates for this treatment. Secondly, the effects of ketamine abuse include many immediate side effects such as:

• Psychedelic symptoms (hallucinations, memory defects, panic attacks)
• Nausea/vomiting
• Sleepiness
• Increase in heart rate and blood pressure
• Liver damage

And the recreational use of ketamine has also brought to light the possible side effects of:

• Bladder complications
• Kidney complications
• Pathological psychiatric behavior
• Memory deficits

So, unfortunately, while ketamine appears to be a very promising medication in terms of speed to antidepressant effect, it doesn’t appear to be a sustainable treatment in the long run right now.