What’s So Special About K仔?

Ketamine [K仔] was almost unheard of in Hong Kong about a decade ago.  However, K仔 [pronounced: ‘K Jai’] has now taken over as the most popular recreational drug* as well as catching the public’s attention after the tragic deaths of a small number of young people were widely reported in the Hong Kong media.

The media has keenly followed any incidents involving young people and ketamine. One incident that was widely reported in 2009, involved a teenage girl from Hong Kong who was filmed on a mobile phone snorting a long line of Ketamine in a mainland China disco. The girl apparently died as a result of overdosing on Ketamine. However, evidence is yet to be produced that substantiates these rumours.  The death of two young men [aged 23 & 25 years old] who died within two hours of each other, was another incident that was widely reported in the Hong Kong media.

Video [Cantonese]: Hong Kong media report of two suspected ketamine-related deaths

At a time when there is potential for a moral panic in Hong Kong, this article aims to provide accurate information about the current risks and consequences of ketamine use and dispel any myths in the process.

Situation in Hong Kong

  • There were 4,473 reported Ketamine users in Hong Kong during 2010.
  • Of these, 2,376 were newly reported ketamine abusers (1,367 were under the age of 21)

Data source: Central Registry of Drug Abuse (2010)

What is Ketamine?

Ketamine Hydrochloride [K仔, Special K, Kit Kat, Vitamin K, K] was created for use in 1962 as a human anaesthetic and can be found in most hospitals around the world. Ketamine is used for the treatment of radiation, burn therapy and for children who have adverse reactions to other anesthetics as it does not have as deep a sedative effect as alternative medications. It is also commonly used in veterinary medicine.

Ketamine belongs to a class of drugs called ‘dissociative anaesthetics’. These can separate perception from sensation and results in feelings of detachment from the environment and self. Ketamine has been limited in clinical use by this hallucinogenic effect (known as ’emergence delirium‘) which was described during its first human volunteer trial (Domino et al., 1965). Ketamine is widely manufactured in liquid form in China and then brought into Hong Kong where it is converted into powder form.

How is it taken?

  • Ketamine is often taken intranasally (snorted). The effect comes on within about 5-10 minutes. See below table 1 for details about the time taken for onset of effect and how long the effect lasts
  • Other methods vary in amount of time it takes to produce effects: injection is the fastest and onset occur within seconds. If swallowed, the effects of Ketamine come on between 15-20 minutes.
  • Ketamine is dose specific. This means that the amount taken will determine the degree and type of effect the drug will have.
  • If Ketamine is injected into the muscle then less is needed to enter the K-hole. Ketamine should not be injected intravenously [into veins]

Table 1: Ketamine Pharmacokinetics based on route of administration [click to enlarge]


What are the effects?

  • The effects of ketamine will vary depending on a number of factors [weight, dose, route of administration, tolerance, whether taken in combination with other substances]
  • At lower doses it can increase heart rate and can cause a dreamy feeling that has been described as being similar to nitrous oxide. Users report feeling floaty and slightly outside their body.
  • Higher doses produce a ‘trippy’ hallucinogenic effect, and may cause the user to feel detached from their body. This state is known as the ‘k hole’. In medical terms, this dissociative anaesthesia is caused by electrophysiological dissociation between the limbic and thalamoneocortical systems (Sarjbeet et al. 2011).
  • A Ketamine trip usually lasts between 45 and 90 minutes. However, the experience can be shorter if the user has high tolerance.

Video: Hong Kong Government Ketamine TV campaign

What is the ‘K Hole’?

When taking a higher dose of Ketamine, then a user can experience a sensation that is described as if they are rising above their own body. This is known as ‘entering the K hole’.  Some users find the experience enjoyable but there are some that find it frightening. While in a K-hole, a user will usually remain seated or lying down during the experience. Arms and legs may feel numb in the initial stages of the trip.  In 10-20 minutes  user may find themselves hardly able to move and, at higher doses, the experience has been described as even approaching out-of-body and near-death experiences. This effect is a result of Ketamine separating or dissociating the mind from the body, and in effect the brain is freed from reacting to sensations from the body. Simply put, perception increases to fill the gap vacated by the senses and gives rise to Ketamine’s more mind-expanding effects.

What happens after taking Ketamine?

  • A ‘K’ user might feel wiped out and not ready for anything too loud or too demanding. Sometimes they may feel pretty disoriented. However, some people report feeling energised after a Ketamine trip and want to move around, dance or stretch.
  • It’s not uncommon to have a memory lapse about the details of the trip. This is similar to that of not being able to remember a dream the next day, even though the experience may have been pretty intense at the time.

How much does Ketamine cost?

  • One packet of ketamine sells for between HK$100-HK$200.
  • It often comes packaged in folded HK$20 notes or coloured paper.

What are the risks of taking K仔?

  • While low doses of Ketamine can increase heart-rate, at higher doses it can depress consciousness and breathing and has an increased risk when taken in combination with depressants (downers) such as alcohol, heroin, GHB and valium
  • Frequent use can potentially lead to disruptions in consciousness and can leave the user vulnerable to being a victim of crime including ‘date rape’.
  • There are potential neuropsychological and neurotoxicity risks. Acute and acute-on-chronic use of ketamine has been shown to be associated with impaired information handling within working memory and episodic memory, as well as semantic processing deficits [Morgan 2006].
  • In the long-term there is evidence for deleterious neuropsychiatric and urological effects. Long-term users can develop poor psychological well-being, memory difficulties, and are at risk of haemorrhagic cystitis with significant associated lower urinary tract symptoms (Sarjbeet et al, 2011). Read research paper on risk of bladder dysfuction and urinary tract abnormalities in Ketamine misusers. Ng et al (2010) conducted a retrospective review of 233 cases of ketamine misusers that had presented to fifteen accident and emergency departments across Hong Kong and found that most ketamine users that presented to the A & E departments presented acutely with transient central nervous system depression, abdominal pain, or lower urinary tract symptoms. There is a debate about whether the emergence of Lower Urinary Tract Symptoms and bladder dysfunction is a result of Ketamine use or whether this can be attributed to the cutting agents that are present in non-pharmaceutical ketamine.  In other words, does ketamine or the metabolites cause inflammation in the kidney or bladder cells that results in inflammation or is this due to other agents present that have affected the quality? Hanna [2010] points out that a conclusion cannot be reached as there have not yet been any controlled studies to show that the incidence of Lower Urinary Tract Symptoms is unusually high among ketamine users compared to otherwise similar populations of non-users.
  • Possession of Ketamine is illegal in Hong Kong. It has been illegal without a prescription since 2000 and possession carries a possible HK$1 million fine and seven years imprisonment.
  • There is an increased risk of accidents from lack of co-ordination.

Video: TV campaign highlighting bladder dysfunction

Closing points to address two common beliefs about Ketamine use in Hong Kong:

Ketamine causes brain damage

Despite the moral panic in the media about the harmful effects of Ketamine, the fact is that the long-term effects of ketamine use are still being investigated. The literature on ketamine-related chronic toxicity including the neuropsychological effects of ketamine misuse is one that is developing. Based on research undertaken to date, there is some evidence to suggest that long term ketamine misuse can result in deleterious neuropsychiatric and urological effects. Sarjbeet et al (2011) concluded that long-term users can develop poor psychological well-being as well as experiencing memory difficulties.

One of the most cited pieces of research for claiming that ketamine use has a detrimental effect on brain activity was conducted by Olney in 1989.  This study reported that ketamine caused ireversible changes in two small areas of the rat brain. However, the findings of this study are limited in their application to humans as there are significant differences in metabolism between a human and rat brain [Tryba & Gehling, 2002].  There is a single large-scale longitudinal study undertaken by Morgan et al (2009) that has shown that heavy ketamine users had impaired verbal, short-term memory and visual memory. However this same study found that occasional ketamine users (those who used Ketamine 1-2 times per month) and ex-ketamine users were not found to differ from controls in the same tests for memory, attention and psychological well-being tests.  This suggests that there might be a difference between heavy and occasional ketamine users in verbal, short-term memory and visual memory impairment.  This study also found that there is a possibility of depression occuring as a result of ketamine use in both current ketamine users and those that were abstinent.

If you take Ketamine you are going to have a bad experience

While some users do have bad experiences after taking ketamine, it needs to be recognised that for quite a number of people in Hong Kong, the experience is actually quite enjoyable and understanding this can help to appreciate why a number of young people choose to take this substance.


* According to official data published in 2010 by the Central Registry of Drug Abusers [CRDA], ketamine is the most popular drug in Hong Kong for reported drug users under the age of 21. Heroin continues to be the most common drug for reported drug users over the age of 21.



Domino, E., Chodoff, P. & Corssen, G. (1965) Pharmacologic effects of Ci-581, a new dissociative anesthetic, in man. Clinical Pharmacology Therapy. 1965;6:279:91.

Hanna J. “KLUTS: Ketamine and Lower Urinary Tract Symptoms”. Erowid Extracts. Nov 2010;19:12-4. Online edition: Erowid.org/chemicals/ketamine/ketamine_article2.shtml [accessed June 24th 2011].

Morgan, C. & Curran, C. (2006) Acute and chronic effects of ketamine upon human memory: A review. Psychopharmacology (Berl). 2006;188:408.24.

Morgan, C., Rossell, S., Pepper, F., Smart, J., Blackburn, J. and Brandner, B. (2006) ‘Semantic priming after ketamine acutely in healthy volunteers and following chronic self-administration in substance users. Biol Psychiatry. 2006;59:265.72.

Morgan, C., Muetzelfeldt, L. and Curran, H. (2009). “Consequences of chronic ketamine self-administration upon neurocognitive function and psychological wellbeing: a 1-year longitudinal study”. Addiction 105 (1): 121

Ng, S., Tse, M., Ng, H & Lau, F. (2010) ‘Emergency department presentation of ketamine abusers in Hong Kong: a review of 233 cases’ Hong Kong Med J 2010;16:6-11

Olney, J., Labruyere, J. and Price, M. (1989). “Pathological changes induced in cerebrocortical neurons by phencyclidine and related drugs”. Science 244 (4910): 1360–2.

Sarbjeet, S., Kalsi,   I.,Wood, D. & Dargan, P. (2011) Emerging Health Threats Journal 2011, 4: 7107

Tryba M, and Gehling, M. (2002). “Clonidine: a potent analgesic adjuvant”. Current Opinion in Anaesthesiology 15 (5): 511–7.


Further Information

A list of services in Hong Kong that work with people who use Ketamine

Media Stories:

Reuters: Hong Kong Drug Addicts Head to China to Pop Pills [June, 2011]

Related Research:

A Review of the Nonmedical Use of Ketamine: Use, Users and Consequences (Jansen, K.L., 2000)

Sit Down to Float: The Cultural Meaning of Ketamine Use in Hong Kong (Laidler & Hunt, 2008)

The destruction of the lower urinary tract by ketamine abuse: a new syndrome? (Chu et al., 2008)


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Categories: Article, Drugs Info, HK Spotlight

11 Comments on “What’s So Special About K仔?”

  1. July 2, 2011 at 12:13 #

    I saw some drug abusers have “infection” on their legs, is that related to Ketamine?

    • July 2, 2011 at 12:22 #

      If somebody is injecting (intra-muscular) Ketamine then there is a risk of infection if good hygiene is not practiced (site kept clean, sterile equipment etc).

  2. Karman
    July 2, 2011 at 12:16 #

    How can they abstain from it?

  3. July 2, 2011 at 13:06 #

    Ahh… the million dollar question (and a good one). K仔 users develop a psychological dependency (rather than physical) and like other drugs where there is psychological dependency then it can be helpful for someone who wants to abstain from K仔 to get some help and support as it is not easy. I have included the details of some services in HK that offer support to ketamine users. These can be found on the HK Treatment Services (Resources) page on this site.

  4. July 2, 2011 at 14:15 #

    The risk of taking Ketamine is getting higher as the quality of such is getting lower and lower as the trafficker will mix other chemical substances in so that they can earn more profit.

  5. Gloria Shum
    July 4, 2011 at 15:18 #


  6. July 4, 2011 at 15:35 #

    Gloria, 多謝你的建議. 我會think about 加一些過來人的故事. 我已經找到了一些香港政府播放關於K仔. I will include shortly 🙂

  7. Clara HO
    July 4, 2011 at 20:26 #

    – As a social worker, we would like to understand more about how ‘K hole’ attracts the teens from the real world.
    – the video of lift embrassment is good material for soical worker, for us to show it to the teens.
    – It would be more intesting to see how exactly the facial expression and body language when people are using K, to help us to identify them.

  8. Sunil H
    July 5, 2011 at 14:26 #

    amazing detail here, especially for parents of teenagers on the fringe

  9. Barias
    March 1, 2012 at 18:28 #

    Spot on with this write-up, thanks for that info.

  10. isaac
    March 4, 2014 at 23:07 #

    A lot of information and inspired me.

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