How Long Does Ketamine and its Antidepressant Effects Last?

One of the advantages of ketamine as a clinical and therapeutic treatment is that it can lead to desired treatment outcomes within shorter timescales — for some within 24 hours, others after weeks of therapeutic work— while maintaining the efficacy and beneficial effects of longer-acting therapeutic and psychedelic experiences.

There are two ways to address the question “how long does ketamine last?”: How long do the “felt effects” —immediate physiological effects— of the medicine persist in the short-term, and how long do its lasting antidepressant and antianxiety effects persist.

How Long Do the Short-Term, Physical Effects of Ketamine Last?

How long ketamine’s immediate physical effects last depends on multiple factors, with the key factor being method of administration. There are a number of ways ketamine can be received, and each one has its own timing for onset of effects, duration of experience, and noticeable effects after the experience.

The duration of the felt effects or “felt experience” depends primarily on the methods of administration.

Methods of Ketamine Administration

Ketamine is administered, or taken, in the following ways: intravenous (IV) infusion, intramuscular (IM) infusion, sublingual tablets, or intranasal spray. 

Treatment sessions using each of these methods are typically set for one hour, with immediate effects subsiding around one to three hours.

Intravenous (IV) infusion 

IV infusion takes the medicine directly into the bloodstream. It has a very rapid onset, and how long the felt experience lasts is dependent on the half-life of ketamine — the time it takes to be processed in the body and leave its system fully— and other psychological factors. Infusion sessions typically last one hour, but can be extended up to five hours based on clinician’s recommendation.

Intramuscular (IM) infusion 

Intramuscular infusions are administered through a syringe, which is injected into a muscle (usually the shoulder or thigh). This method’s onset typically takes 2-4 minutes, and its full duration ranges from 1-3 hours.

Sublingual Tablets or Troches

Tablets or troches (pronounced “tro-keys”) are another way of receiving the medicine. Mindbloom uses rapid dissolving tablets (RDTs), which are held in the mouth for direct oral absorption and removed after a point of maximum absorption. 

By not swallowing the medicine, the gastrointestinal tract is bypassed avoiding metabolization in the liver, which extends the duration of the experience. If not swallowed, the average onset is around 5-10 minutes, with the dissociative effects lasting for around 30-60 minutes, and a return to physical baseline around 1-3 hours after treatment. If swallowed, half-life is increased and the effects last longer, around 4-5 hours.

Intranasal (IN) Spray 

Intranasal spray options, administered through the nose, are also emerging. There are two types of ketamine-based nasal spray: S-ketamine (esketamine) and R-ketamine (arketamine), also known as “racemic” or “generic” ketamine.

This method’s onset typically takes five to ten minutes, and its full duration ranges from one to three hours.

How Long Does Ketamine Stay in Your System?

As with any compound, it’s easiest to consider this in terms of the half-life of ketamine. A half-life is how long it takes for 50% of the compound to be excreted from the body.

Ketamine metabolizes quickly in the body, with a half-life of around 2.5 hours. This means that after 2.5 hours, 50% of the ketamine has been excreted from the bloodstream. For comparison, coffee has a half-life of five hours. Ketamine’s metabolites can remain in the body for almost two weeks.

Given this, after about 10-12 hours since the initial dosing, a majority of the ketamine is out of your system. This is independent of the subjective experience, which subsides after about an hour.

Overall, this is one of the advantages to work with ketamine: it’s very well tolerated across a large population, it has a fast onset and manageable total duration, and is metabolized and processed through the body quickly as well.

How Long do the Antidepressant Effects of Ketamine Last?

One of the most remarkable aspects of ketamine therapy are the benefits that an individual can experience during, after, and between each dosing session. This is called the “durability” of the experience.

After a single session, it would be reasonable to expect a general improvement in mood/outlook, and increased mental flexibility and openness lasting for about seven days. This can vary from person to person. Some effects are noticeable immediately after the session.

A 2019 study on individuals with major depressive disorder demonstrates the potential for longer-term positive effects:

“There was a significant improvement in depression, anxiety, and the severity of illness after 2 weeks and 1 month of the last dose of ketamine. Significant improvement at 1st [hour] of the first dose was seen in depression and anxiety and not for illness severity. There were transient adverse effects observed in some patients which subsided within 1 [hour].”

Given the 1-2 week window of increased openness, flexibility, and general mood brought on by a single session, another opportunity presents itself when “stacking” or adding on multiple sessions through the course of treatment.

Integration’s role in ketamine therapy’s effectiveness

It’s worth noting that ketamine as a compound alone isn’t a “magic pill.” Its short and long-term effects are meant to open an individual up to action and behavioral changes that will help them reach their full potential. Ketamine therapy as a holistic experience promotes setting and working on intentions or goals that promote personal growth. These insights gained are taken with us but the physiological effect may not last.

Mindbloom’s introductory program includes six sessions, generally spaced 1-2 weeks apart. This treatment methodology is referred to as “stacking.” By continually renewing this general baseline improvement, paired with effective integration work in-between, clients report improvement and maintenance of their baseline moods for many months after completing their last session.

Overall, we can see there are acute effects from a single session that can last for weeks. If sessions are combined into a comprehensive and holistic program, the enduring effects can last for months, or provide enduring and robust baseline improvements.

How Long Do Ketamine Treatments Last?

In general, the subjective experience tends to follow a standard direct dosing arc: An initial period for the effects to come on, a period of full experience with an associated ‘peak’, and a gradual decline back towards normal waking consciousness — though with some lingering physical effects that subside 1-2 hours after the session.

Each individual will have a unique experience, and each session may slightly vary from these exact markers, though the general trend tends to remain the same. Here is a common overview of the experience:

• 0 to 15 minutes: dosing and initial effects begin to arise.
• 15 to 45 minutes: full effect onset, peak of subjective experience.
• 45 minutes to 1 hour: gradual decline back to waking consciousness.
• 1 hour +: residual effects (grogginess, mild dizziness, etc.) begin to subside.
  

Most treatments are designed to last roughly one hour, with a recovery window of up to three hours.

Clients should plan to have a restful day after a ketamine session, regardless of the delivery method used. It’s helpful to stay with the medicine and the experience rather than jumping back into work or stressful exercise.

If you'd like to learn more about the psychedelic therapy experience, read about how the Mindbloom journey works.