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How Long Does Ketamine Stay In The System?

Ketamine half-life

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Table of Contents

Ketamine’s Time Of Staying In The System

Ketamine has a short half-life of around 2.5-4 hours, which means that it takes about 13.45-16.30 hours to eliminate the drug from the system. Although Ketamine shouldn’t stay for more than 24 hours, some users need up to few days to get clean. Factors, such as metabolic rates and age, affect the duration and elimination of the drug.

False Positive for PCP After Ketamine

No. Although Ketamine is an analog of PCP, one can’t get a false positive result. In general, standard tests do not detect Ketamine. Note that some specialized techniques can identify Ketamine (swab test – up to 24 hours, blood tests – up to two weeks, hair tests – up to 90 days, and urine tests – up to four days).
Ketamine is a potent analgesic that’s often abused due to its sedative properties. Nevertheless, standard drug tests do not detect Ketamine.
When it comes to powerful drugs, it’s important to know more about their duration and elimination. Ketamine half-life is 2.5-4 hours, which means one’ll need 13.45-16.30 hours to eliminate the drug from the plasma. Interestingly enough, children need only around 11 hours to get clean from the drug.
In general, most users need between 24 hours and a few days to clean their system from Ketamine.

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Factors That Affect Ketamine Duration & Elimination

Like any other drug, the effects Ketamine has on people vary between individuals. Many factors influence the duration and elimination of the drug:

  • Dosage
  • History of abuse
  • Weight
  • Age
  • Overall health
  • Metabolic rates
  • Genetics
  • Lifestyle

As Ketamine is metabolized by the CYP3A4 isoenzyme within the liver and as this enzyme is regulated by the CYP3A4 gene, it’s interesting to mention that some genetic differences affect the elimination of the drug.
Also, we should mention that Ketamine is lipophilic. That means that the drug accumulates in fat stores, which can lead to a lengthy elimination process.

Ketamine Metabolism Period

Ketamine is metabolized by the liver. Its primary metabolites are norketamine and dehydronorketamine, which have shorter elimination half-lives than Ketamine.
ketamine stay
However, note that in patients with brain or spinal cord injury, these half-lives are longer when compared to Ketamine (5.3 for norketamine and 6.9 hours for dehydronorketamine).
As mentioned above, Ketamine is subject to hepatic metabolism. The drug undergoes N-demethylation via the CYP3A4 isoenzymes. Then, Norketamine forms the secondary metabolite – dehydronorketamine.
90% is excreted via urine and 3-5% via feces. Note that only 2-4% is unchanged Ketamine, which makes urinalysis not so popular.

Ketamine & Drug Testing

Although standard tests can’t detect Ketamine, some specialized techniques can find Ketamine in the body.

How Long Does Ketamine Stay In The Blood?

Although Ketamine has a short half-life, the drug can be detected in the blood for up to two weeks. However, blood tests for Ketamine are rare: they might be too expensive and time-consuming.

How Long Does Ketamine Stay In The Saliva?

Saliva tests are more popular and noninvasive when compared to blood tests. In fact, one can choose from various kits and purchase them online. Ketamine can be detected in the saliva for up to 24 hours.

How Long Does Ketamine Stay In The Hair?

Hair tests usually provide a longer window of detection (up to three months). Ketamine can be found in hair samples. The cut-off levels for Ketamine are 0.5 ng/mg and 0.1 ng/mg for norketamine.

How Long Does Ketamine Stay In The Urine?

Urine tests can detect Ketamine for up to four days and norketamine for up to two weeks. In fact, researchers claim that norketamine can remain detectable in monkeys for up to 31 days.
Note that although Ketamine is an analog of PCP, the drug won’t give a false positive test on standard drug tests.
To be on the safe side, do not mix drugs and take medications only as prescribed.

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About Author

Peter Grinspoon, MD

Dr. Peter Grinspoon is an experienced physician with long-term clinical practice experience. As a former analgesic addict, Dr. Grinspoon knows precisely how important it is to provide patients with effective treatment and support. Medical writing for him is the way to communicate with people and inform them about their health.


Leave a comment

  • Michael swehla
    Dear sir/ma’am, My psychiatrist told me that ketamine would only be detectable in my ur in for 24 hours. You state that it could be detected for up to 4 days. I have an appt with my pain management doctor only 3 days after my ketamine infusion. 120mg. Would I go ahead and keep that appt or postpone it? Thank you, MICHAEL C SWEHLA, MSgt, USAF
    • Jack
      If you’re receiving a ketamine infusion for depression, I only assume because you stated your psych advised you on detection times, you will be fine. The ketamine will, should, be out of your system but the metabolite norketamine can be detected for up to 7-14 days, depending on the dose/frequency. The reason I say you’ll be fine is you’re receiving an infusion from a qualified medical professional, all you need to do is bring proof to your pain Dr and that would explain the findings in your urine. For example, I take anti anxiety meds and test positive for benzos when I see my pain Dr, I have my prescription on file so he knows I’m not abusing meds. The only thing I would be cautious in is that I’ve read cheaper quality urine tests can give a false positive for pcp as nor ketamine is very closely related, but 96 hrs is a good buffer. The reason I get screened every month instead of every three months is because a year ago I showed positive for MDAA, a common additive in pre workout energy drink. But it metabolizes into the same indicators for bath salts. So, be careful.hopefully this was helpful and sorry it was so late.
  • Mbulelo
    How does ketamine stay in ur brain blood barrier
  • Ukjay
    I had a positive urine sample for ketamine after 12 days
  • Jeremy
    How long is ketamine detectable in sweat? For instance if a drug sweat patch is used?
  • Denise
    Hi, I’m randomly drug tested and the last time, they used a mouth swab instead of urine since my bladder was empty. The specimen was also outsourced to a different lab than they usually use. The vial was laying on the receptionist desk when she handed it to me and asked me to swab my mouth as I sat there. Afterwards, she placed it back in the empty vial which had no markings or my name on it when I last saw it. Ketamine, Norketamine and Fentanyl showed up on the tests. I take none of these drugs. I never heard of Ketamine in my life. I have heard of Fentanyl. I asked the lab to rerun the tests with my sample. They can only do it if 1. They still have it. 2. If there’s enough to test. I also asked that they check for possible cross-contamination with another specimen or confirm it was really mine (check the name, numbers, etc with the paperwork). The other issue with the test was that 3 of the 4 drugs I do take as prescribed, didn’t show up on the test. I further researched the Norketamine and found it was a metabolized result from the Ketamine. I confirmed this with the doctor at the lab. He called as I was writing this and said my specimen was destroyed so he can’t retest or confirm they even had the correct vial. I asked why the Fentanyl didn’t have its associated metabolized version of Fentanyl like the Ketamine and he said most likely, the amount was too low (below their cutoff). I asked him to find out if his statement is accurate by checking the amount. Because, it’s strange to me that one drug would metabolize in a liver and another wouldn’t. I additionally asked him to find out if there were any other drugs detected in the specimen but not reported because they were below their cutoff (which should be the case if this was my actual vial). That still doesn’t rule out cross contamination obviously, since I never took those other drugs. I hope someone can answer the following questions for me: 1. How common is illegal Ketamine use in Pittsburgh, PA? 2. How would a person get the drug? I don’t want to know specifics but only if it’s as easy as walking out my door, going to a known drug area and asking for it. Is it common enough that someone would have it in their pocket to sell? 3. Is there a way to get false positives for Ketamine and Fentanyl? If so, how? 4. Are there any drug combinations that might cause a false positive? I’m faced with having all my meds taken from me. My doctor won’t refill some that I need already. I’ve been ill as a result of going cold turkey which may kill me. I’m a disabled senior citizen with agoraphobia (fear of leaving my house) now having my drug test show up with 2, actually 3 drugs I never heard about in my life which has caused my doctor to terminate my medications per the PA law. I also suffer from severe Asthma which after reading about Ketamine, can kill someone with respiratory problems if they took it, I’m still alive. I also take Lorazepam which I read is the most dangerous to take with Ketamine and most likely will cause death, I’m still alive. Please, I need some help. I’m at the mercy of a new testing facility, new method of testing, and my specimen has been destroyed so it can’t be confirmed as mine. I’ve been on pain and anxiety medication for 13 years. I’ve never had a bad drug screening, I don’t drink alcohol. I use yoga, acupuncture and low level exercise as a holistic method of controlling my pain and anxiety along with the meds. My medication is as low as I possibly can handle and feel I’ve found a good balance. My doctor and I have experimented with some anti-depressant drugs and low dose steroids as an alternative method for pain. The steroids were causing problems and the anti-depressants I took caused respiratory issues. Only I know that I didn’t take the Ketamine, Norketamine and Fentanyl. I just have to prove it. Thanks!
    • Adam
      Do you have a solution would be for them to redo the test. Considering your age and situation, it doesn’t seem unreasonable. If you were so inclined, you could find ketamine. Fentanyl usually shows up because it’s mixed with heroin.
    • Adam Vasilakis
      The real kicker for them messing up your tests are the drugs that are SUPPOSED to be there are not. On the other hand, having drugs that are supposed to be in your system and are not is a red flag because you either took them not as prescribed or the drs think other people have the drugs if there not in your system.
  • Ashley
    Thank you so much for this information.
  • Tommy martin
    I had ketamine show up on my oral swab test I have never touched ketamine never really knew what it was is there such thing as false positive for ketamine