No. Ketamine is not an opioid. It is a dissociative anaesthetic and NMDA receptor antagonist — a completely different class of drug with a fundamentally different mechanism of action in the brain. Ketamine does not bind to opioid receptors in the way opioids do, and an opioid-blocking drug such as naloxone cannot reverse its effects. Understanding what ketamine actually is matters, because the risks, the signs of dependence, and the path to treatment are all different from the opioid pathway.
This article explains what class of drug ketamine belongs to, how it works, what it does to the body and brain, and what happens when use becomes a problem.
What Class of Drug Is Ketamine?
Ketamine belongs to the class of drugs known as dissociative anaesthetics. Its medical name reflects this: it was developed in the 1960s as a safer alternative to phencyclidine (PCP) for use in surgical anaesthesia, and it remains a licensed medicine used in hospitals and veterinary settings today.
In terms of pharmacology, ketamine is an NMDA receptor antagonist. NMDA stands for N-methyl-D-aspartate. These receptors are part of the glutamate system, the brain’s main excitatory neurotransmitter pathway. Blocking NMDA receptors produces sedation, analgesia (pain relief), and the dissociative effects that give the drug its distinctive character.
In the UK, ketamine is a Class B controlled substance under the Misuse of Drugs Act 1971. It was reclassified from Class C to Class B in 2014, reflecting the TALK TO FRANK ketamine page guidance that possession without a prescription carries a penalty of up to five years’ imprisonment. Supply carries up to 14 years.
Beyond recreational use, ketamine has legitimate medical applications: surgical anaesthesia, procedural sedation, and — at sub-anaesthetic doses — treatment-resistant depression. Esketamine (a derivative) is licensed in the UK for depression under the name Spravato. This medical context is part of why the drug sits in a complicated cultural space.
How Ketamine Works: The NMDA Receptor Explained
To understand why ketamine is not an opioid, it helps to know how each type of drug acts in the brain.
Opioids (morphine, heroin, codeine, fentanyl) work by binding to opioid receptors, particularly the mu opioid receptor. These receptors are distributed throughout the brain, spinal cord, and gut, and activating them produces pain relief, euphoria, and sedation. They are also responsible for opioid tolerance, physical dependence, and the life-threatening risk of respiratory depression in overdose.
Ketamine works by an entirely different pathway. It is a non-competitive antagonist of NMDA receptors, which are activated by glutamate. Ketamine enters the NMDA receptor channel when it is open and blocks it, reducing the effect of glutamate signalling in the central nervous system. According to the ACMD’s updated review of ketamine use and harms, this produces dissociative effects and may also contribute to antidepressant properties by promoting neural connections, particularly in the prefrontal cortex.
Critically, ketamine is not known to cause the respiratory depression associated with opioid overdose. And naloxone, the opioid-overdose reversal drug, has no effect on ketamine’s analgesic action in humans. These two facts confirm that the mechanisms are categorically different.
Why People Confuse Ketamine With Opioids
The confusion is understandable. Both ketamine and opioids are used medically for pain and as anaesthetic agents. Both alter consciousness. Both carry addiction potential. Both are misused recreationally. On the surface, they seem to occupy a similar space.
But the similarities stop there. The underlying biology, the overdose profile, the withdrawal experience, and the physical risks diverge significantly. Opioids carry a clear risk of fatal respiratory depression in overdose. Ketamine does not suppress breathing in the same way, though at very high doses or in combination with other CNS depressants, it can still carry some respiratory risk. Opioid withdrawal involves a predictable, physically gruelling syndrome (sweating, vomiting, muscle pain, profound discomfort). Ketamine withdrawal is primarily psychological.
Ketamine is sometimes grouped in conversation with dissociative drugs like PCP and nitrous oxide, or with synthetic drug addiction in the broader category of substances that distort perception. These groupings are more pharmacologically accurate than placing it alongside opioids.
What Does Ketamine Actually Do? Effects and Risks
At recreational doses, ketamine produces a distinctive cluster of effects that set it apart from most other substances. When snorted, effects typically begin within 15 to 20 minutes and last roughly 30 to 60 minutes, though the precise duration depends on dose and route of use.
Common short-term effects include:
- A sense of detachment from the body and surroundings (dissociation)
- Hallucinations and distortion of time, space, and perception
- Euphoria and relaxation
- Confusion, drowsiness, and slurred speech
- Nausea and vomiting
- Numbness and loss of coordination
- Amnesia (difficulty forming memories during the episode)
The FRANK guidance notes that ketamine can increase heart rate and blood pressure, which carries particular risk for people with heart conditions or high blood pressure. Because ketamine causes numbness, users who injure themselves during intoxication may not feel or notice the injury.
Memory problems with regular use are also documented. Long-term heavy use has been associated with cognitive difficulties, including problems with concentration and recall.
The K-Hole: What It Is and Why It Matters
At high doses, ketamine can cause an experience commonly called a K-hole. This is a state of extreme dissociation in which users describe feeling as though the mind has separated entirely from the body. The ability to move, communicate, or respond to the outside world is severely impaired.
The FRANK guidance describes it as feeling like “your mind and body have separated and you can’t do anything about it,” which can be a deeply frightening experience. A K-hole typically lasts between 15 and 45 minutes, though the disorientation may persist beyond this.
The danger is not just psychological distress. A person in a K-hole is physically vulnerable: unable to seek help, call for assistance, or protect themselves from harm. The combination of numbing effects and profound loss of coordination creates a real risk of accidental injury. Unlike an opioid overdose, there is no reversal agent.
Ketamine and Bladder Damage: A Serious and Often Overlooked Risk
One of the most serious and distinctive risks associated with ketamine use is damage to the urinary system. Ketamine-induced uropathy (sometimes called ketamine bladder syndrome or ketamine cystitis) is a condition in which long-term ketamine use damages the urothelial cells that line and protect the urinary tract.
According to the NHS East Kent ketamine patient information leaflet, ketamine damages the bladder causing inflammation and ulceration. Symptoms include:
- Frequent urination with small volumes
- Severe urgency and inability to hold urine
- Pain in the bladder and kidneys
- Blood in the urine
- Incontinence
The ACMD review notes that approximately a quarter of people who use ketamine regularly report at least one urinary symptom. A systematic review published on PubMed found rates of lower urinary tract symptoms in heavy ketamine users reaching as high as 49.5% in some clinical study populations.
Damage is dose-dependent and cumulative. The NHS guidance is clear that even occasional use can cause early changes. With continued daily use, the damage can become irreversible. In severe cases, surgical removal of the bladder has been required.
The primary treatment is stopping ketamine entirely. Early-stage damage may improve substantially with complete cessation. If you or someone you know is experiencing any of these symptoms, it is important to speak to a GP or visit an urgent care setting, as progression without medical input can cause permanent kidney damage.
Can You Become Addicted to Ketamine?
Yes. Ketamine can cause dependence, though its profile differs from opioid addiction in important ways.
The dependence that develops with regular ketamine use is primarily psychological. Users develop tolerance over time, requiring larger quantities to achieve the same dissociative effect. Cravings, difficulty cutting down, and continuing use despite negative consequences are recognised features of ketamine use disorder.
What ketamine does not typically cause is the severe physical withdrawal syndrome associated with opioids, alcohol, or benzodiazepines. There are no seizures, no life-threatening physical crisis on cessation. Withdrawal from ketamine tends to involve mood disturbances, anxiety, cravings, and cognitive difficulties. This can still be deeply uncomfortable and difficult to manage alone, but the medical risk profile is different.
What is changing is the scale of the problem in England and Wales. Treatment services are seeing substantial increases in people seeking help with ketamine use, which reflects both rising use and rising awareness that help is available. Our page on ketamine addiction treatment explains the signs of dependence and what treatment involves in more detail.
Ketamine Is Rising in England and Wales: What the Data Shows
Ketamine use in England and Wales has been increasing, and the harms associated with it are being seen more frequently in clinical settings.
According to the adult substance misuse treatment statistics 2024-25 from OHID, the number of adults entering treatment with ketamine as a primary problem stood at 5,365 in 2024-25. This is more than 12 times the figure from 2014-15. The ACMD review reports that an estimated 264,000 people aged 16-59 used ketamine in England and Wales in 2024-25, with use particularly concentrated among 16-24 year olds (2.0% of this age group). There were 60 ketamine-related deaths recorded in England and Wales in 2024.
These figures do not make ketamine the most commonly used drug in England and Wales. But the trend is clear, and the associated harms, particularly urinary damage and psychological dependence, are increasingly presenting in NHS settings. The 12-fold increase in treatment referrals over a decade reflects both a genuine rise in problematic use and a shift in how ketamine is perceived by users who need help.
What Treatment for Ketamine Dependence Looks Like
Because ketamine is not an opioid, treatment does not involve opioid substitution therapy (such as methadone or buprenorphine). There is no equivalent substitution pathway for ketamine. Treatment is instead focused on:
- Supported cessation: stopping ketamine use, with clinical monitoring during the early period. Withdrawal is not medically dangerous in the way opioid or alcohol withdrawal can be, but psychological symptoms can be significant enough to warrant support.
- Psychological therapy: cognitive behavioural therapy (CBT) and dialectical behaviour therapy (DBT) are the evidence-based approaches most commonly used. These address the patterns of thought and behaviour that maintain use.
- Dual diagnosis assessment: many people using ketamine heavily have co-occurring depression, anxiety, or trauma. Addressing these alongside the ketamine use is important for sustainable recovery.
- Bladder and physical health review: anyone with a history of heavy ketamine use should have their urinary function assessed. The NHS leaflet emphasises that cessation is the primary intervention for bladder damage.
Residential treatment allows all of these elements to be addressed in a structured, supported environment, away from the cues and contexts that maintain use.
Getting Help at Sierra Recovery
Sierra Recovery is a small private residential clinic in the mountains of inland Andalucía, Spain, backed by PROMIS Clinics in the UK. We treat substance use, including ketamine dependence, alongside mental health conditions within an integrated programme.
Our ketamine addiction treatment approach combines medically supervised support during the initial phase with evidence-based therapy drawn from CBT, DBT, and EMDR. Our drug detox programme is doctor-supervised, and our residential treatment programme follows detox with individualised therapy in a small group setting.
The clinical team is English-speaking throughout. Aftercare, including in-person sessions through PROMIS UK’s London touchpoint, continues after you leave Spain.
For many UK clients, treating ketamine dependence away from the familiar environment where use has become embedded can make a meaningful difference. The cortijo setting in the Sierra de Humilladero, the combination of structured therapy and a genuinely different pace, and the clinical standard of care all serve a specific purpose in early recovery.
Concerned about ketamine use? Talk to our team in confidence. We answer questions about drug and alcohol treatment honestly, in English. PROMIS Clinics-backed care, medically supervised detox, residential programme in Andalucía, London-based aftercare. Speak to our team UK: +44 1202 653136 | Spain: +34 666 777 888 Confidential. English-speaking team. No obligation.
Sources
- TALK TO FRANK. “Ketamine.” https://www.talktofrank.com/drug/ketamine
- Advisory Council on the Misuse of Drugs (ACMD), GOV.UK. “Ketamine: an updated review of use and harms.” https://www.gov.uk/government/publications/ketamine-an-updated-review-of-use-and-harms/ketamine-an-updated-review-of-use-and-harms-accessible
- Office for Health Improvements and Disparities (OHID), GOV.UK. “Adult substance misuse treatment statistics 2024 to 2025: report.” https://www.gov.uk/government/statistics/substance-misuse-treatment-for-adults-statistics-2024-to-2025/adult-substance-misuse-treatment-statistics-2024-to-2025-report
- NHS East Kent Hospitals University NHS Foundation Trust. “Ketamine addiction and ketamine bladder and induced cystitis.” https://leaflets.ekhuft.nhs.uk/ketamine-addiction-and-ketamine-bladder-and-induced-cystitis/html/
- Tan E, et al. “Systematic review and meta-analysis of ketamine-associated uropathy.” BJU International, 2023. https://pubmed.ncbi.nlm.nih.gov/36464318/
