Khat (also known as qat or chat) comprises the leaves and fresh shoots of Catha edulis Forsk, a flowering evergreen shrub cultivated in East Africa and the South-West Arabian Peninsula. Khat leaves are typically wrapped as a bundle in banana leaves. The principal active components in khat are cathinone and cathine (norpseudoephedrine) (see also Drug profile on synthetic cathinones). Chewing khat releases these substances into the saliva; they are rapidly absorbed and eliminated. Both cathinone and cathine are closely related to amphetamine, and the pharmacological effects of cathinone are qualitatively similar to those of amphetamine, although it is less potent. Only fresh leaves are chewed, because cathinone soon degrades into old or dry plant material. Analysis relies on the characteristic appearance of khat and the presence of cathinone and/or cathine. Khat is not under International control, but is scheduled by some Member States. Cathinone and cathine are listed in the 1971 United Nations Convention on Psychotropic Substances under Schedules I and III respectively.
Molecular structure: Cathinone
Molecular formula: C9H11NO
Molecular weight: 149.19 g/mol
Molecular structure: Cathine
Molecular formula: C9H13NO
Molecular weight: 151.21 g/mol
The principal active component in khat is S-cathinone, otherwise known as (-)-2-aminopropiophenone or, more formally, S-(-)-2-amino-1-phenyl-1-propanone. Cathinone is labile and is transformed within a few days of harvesting to a dimer (3,6-dimethyl-2,5-diphenylpyrazine). It is for this reason that khat needs to be consumed while still fresh. Cathine (1S, 2S-norpseudoephedrine), a further psychoactive substance, arises from the metabolism of cathinone in the mature plant. Apart from common plant products such as tannins, terpenes, flavonoids and sterols, a number of other substances occur in khat including smaller amounts of 1R, 2S-norephedrine and a large number of cathedulins (polyhydroxylated sesquiterpenes). Both cathinone and cathine are close chemical relatives of the phenethylamines. Thus cathinone is the β-keto analogue of amphetamine. A large number of synthetic cathinone derivatives have been produced, some of which have found use as active pharmaceutical agents.
Khat is usually supplied as a bundle of leaves and fresh shoots wrapped in banana leaves. It is reported to have a sharp taste and an aromatic odour. Alcoholic extracts (tinctures) of khat have occasionally been reported, especially in ‘herbal high’ sales outlets and at music festivals.
Both cathinone and cathine are central nervous system (CNS) stimulants, but have a lower potency than amphetamine. Khat consumption leads to effects that are qualitatively similar to those of amphetamine, i.e. increased blood pressure, a state of euphoria and elation with feelings of increased alertness and arousal. This may be followed by depression, irritability, anorexia and difficulty in sleeping. Frequent use of high doses may evoke psychotic reactions. Gastrointestinal effects include constipation and urine retention. The role of other constituents of the khat plant is less well understood. The euphoric effects of khat start after about one hour of chewing. Peak plasma levels of cathinone are obtained 1.5 to 3.5 hours after the onset of chewing. The mean plasma level may reach 100 ng/ml after chewing 60 g fresh khat for one hour. Cathinone is barely detectable in blood after eight hours. First-pass metabolism of cathinone in the liver leads to the formation of norephedrine. Only 2 % of cathinone is excreted unchanged in the urine. The elimination half-life of cathinone is 1.5 +/– 0.8 hours and that of cathine 5.2 +/– 3.4 hours. Specific associations have been proposed between khat consumption and myocardial infarction, liver failure and oral cancer, but in many cases confounding effects could not be eliminated.
Khat comprises the leaves and fresh shoots of Catha edulis Forsk, a flowering evergreen shrub cultivated in East Africa and the Arabian Peninsula. It is usually imported into Europe via air freight.
Although khat can be ingested as an infusion or smoked, by far the most common route of administration is to chew the plant. Fresh vegetable material (stems, leaves and flower buds) is chewed and the juice of the masticated material is swallowed, while the residues are spat out. Typically, an individual consumes 100–200 g of khat leaves (one bundle) in a session, and its effects last for several hours. Infusions from dried leaves are also consumed. With the exception of tobacco, the concomitant use of other drugs, including alcohol, by khat users is uncommon.
Khat is also known as qat, chat, miraa, murungu and Arabian or Abyssinian tea.
Although a bundle of khat appears reasonably characteristic, botanical and microscopic features are of limited use in confirming identity. It is usual for laboratory analysis to confirm the presence of cathinone and/or cathine.
Fresh khat contains around 0.1 % cathinone and smaller amounts of cathine. Although khat comprises an inhomogeneous plant preparation, it is not normally adulterated with other material.
Khat has been reviewed by the WHO Expert Committee on Drug Dependence (ECDD) on a number of occasions, the most recent assessment being made at the 34th meeting of ECDD in 2006. However, Catha edulis remains outside international control, although cathinone and cathine have been listed in the 1971 UN Convention under Schedules I and III respectively since the early 1980s. Khat is controlled in a number of European countries including Belgium, Denmark, Germany, Greece, France, Ireland, Italy, Latvia, Lithuania, Poland, Slovenia, Finland, Sweden, Norway, and Switzerland.
Khat chewing is a traditional practice in Yemen and certain East African countries. Nevertheless, khat use is sporadically reported in Europe as a substance of choice among immigrants from Somalia, Ethiopia, Kenya and Yemen. There are a few published studies of khat use by immigrant communities in European countries. However, these have mostly been conducted in the UK, and it is unclear to what extent their findings can be assumed to reflect patterns of use elsewhere in Europe. Such reports are subject to sampling bias due to the way in which interviewees are recruited. Nonetheless, the studies available do point to significant levels of use within some migrant communities. For example, a study found that in 2005, among the Somalis interviewed, 34 % had used khat in the month prior to the interview although less than 4 % reported using the drug on a daily basis. Studies generally report more use of the plant among males, generally in group settings. There may be a tendency to under-report khat use among women, which is a more stigmatised behaviour and more likely to occur at home or alone. Most studies have suggested that khat users are unlikely to use other psychoactive substances, which distinguishes them from most other groups of recreational drug users in Europe, where polysubstance patterns of use are increasingly the norm. Use of khat among Somali communities has also been reported in Denmark (around 1 350 users) and Sweden (2 000–3 000 users).
In the United Kingdom, a bundle of khat sells for around EUR 5, but the price is higher in countries where it is controlled. Possibly due to the lability of cathinone, khat leaves seem not to be commonly sold over the Internet, whereas Internet sales of khat seeds have been observed.
Khat is used as a traditional medicine by some indigenous people of East Africa, but neither khat nor its isolated active ingredients have been widely recognised for their therapeutic use.
In Germany, preparations of cathine containing up to 5 % as solution (maximum dose 1 600 mg per packaging unit) without any other narcotic substances or per unit dose up to 40 mg cathine, calculated as base, are exempted from special prescription and may be prescribed by ‘normal’ medical prescription. In the UK, khat is licensed as a medicinal product under the Medicines Act 1968, but to date it has not been imported as a medicinal product.
Advisory Council on the Misuse of Drugs (2005) Khat (Qat): Assessment of risk to the individual and communities in the UK, Advisory Council on the Misuse of Drugs, Home Office, London. Available at: http://www.homeoffice.gov.uk/publications/drugs/acmd1/khat-report-2005/
Ahmed, A.G. and Salib, E. (1998) ‘The khat users: a study of khat chewing in Liverpool's Somali men’, Medicine, Science and the Law 38, pp. 165–169.
Al-Hebshi, N. N. and Skaug, N. (2005) ‘Khat (Catha edulis): An updated review’, Addiction Biology 10, pp. 299–307.
Balint G.A. and Balint, E. E. (1994) ‘On the medico-social aspects of khat (Catha edulis) chewing habit’, Human Psychopharmacology 9, pp. 125–128.
Bhui, K. and Warfa, N. (2007) ‘Drug consumption in conflict zones in Somalia’, PLoS Medicine 4 (12), pp. 1865–1866.
Brenneisen, R., Fisch, H. U., Koelbing, U., Geisshüsler, S. and Kalix, P. (1990) ‘Amphetamine-like effects in humans of the khat alkaloid cathinone’, British Journal of Clinical Pharmacology 30 (6), pp. 825–828.
Brenneisen, R., Geisshüsler, S. and Schorno, X. (1986) ‘Metabolism of cathinone to (-)-norephedrine and (-)-norpseudoephedrine’, Journal of Pharmacy and Pharmacology 38, pp. 298–300.
Buffin, J., Mir, Y. and Mirza, I. (2009) Khat: current views from the community around the UK: findings from community engagement forums, National Drugs and Race Equality Coalition. Available at: http://www.docstoc.com/docs/16231066/NDAREC-Khat-Report.
Button, J. and Holt, D. W. (2009) Khat: a bundle of fun or a bunch of problems?, poster presented at the European Science Foundation meeting on khat, Linköping, Sweden, October 2009. Available at: http://www.esf.org/index.php?id=5160.
Corkery, J. M. (2009) The assessment of khat-related deaths in the UK, presented at the European Science Foundation meeting on khat, Linköping, Sweden, October 2009. Available at: http://www.esf.org/index.php?id=5160.
Cox, G. and Rampes, H. (2003) ‘Adverse effects of khat: a review’, Advances in Psychiatric Treatment 9, pp. 456–463.
European Science Foundation (2009) The changing use and misuse of Catha Edulis (khat) in a changing world: tradition, trade and tragedy, presented at the European Science Foundation meeting on khat, Linköping, Sweden, October 2009. Available at: http://www.esf.org/index.php?id=5160.
Feyissa A. M. and Kelly, J. P. (2008) ’A review of the neuropharmacological properties of khat’, Progress in Neuropsychopharmacology and Biological Psychiatry 32, pp. 1147–1166.
Geisshüsler, S. and Brenneisen, R. (1987) ‘The content of psychoactive phenylpropyl and phenylpentenyl khatamines in Catha edulis Forsk of different origin’, Journal of Ethnopharmacology 19 (3), pp. 269–277.
Giannini, A. J., Miller, N. S. and Turner, C. E. (1992) ‘Treatment of khat addiction’, Journal of Substance Abuse Treatment 9 (4), pp. 379–382.
Griffiths, P., Gossop, M., Wickenden, S., et al. (1997) ‘A transcultural pattern of drug use: qat (khat) in the UK’, British Journal of Psychiatry 170, pp. 281–284.
Griffiths, P., Lopez, D., Sedefov, R. et al. (2010) ‘Khat use and monitoring drug use in Europe: the current situation and issues for the future’, Journal of Ethnopharmacology 7 May 2010. [Epub ahead of print], DOI: 10.1016/j.jep.2010.04.046.
Halbach, H. (1972) ‘Medical aspects of the chewing of khat leaves’, Bulletin of the World Health Organization 47, pp. 21–29.
Kalix, P. (1984) ‘The pharmacology of khat’, General Pharmacology 15 (3), pp. 179–187.
Kalix, P. (1990) ‘Pharmacological properties of the stimulant khat’, Pharmacology and Therapeutics 48 (3), pp. 397–416.
Kalix, P. (1994) ‘Khat, an amphetamine-like stimulant’, Journal of Psychoactive Drugs 26, pp. 69–74.
Kalix, P. and Braenden, O. (1985) ‘Pharmacological aspects of the chewing of khat leaves’, Pharmacol. Rev., 37 (2), pp. 149–164.
Kassim, S. and Croucher, R. (2006) ‘Khat chewing amongst UK resident male Yemeni adults: an exploratory study’, International Dental Journal 56 (2), pp. 97–101.
Klein, A., Beckerleg, S. and Hailu, D. (2009) ‘Regulating khat: dilemmas and opportunities for the internal drug control system’, International Journal of Drug Policies 20 (6), pp. 509–513.
Nabuzoka, D. and Badhadhe, F. A. (2005) ‘Use and perceptions of khat among young Somalis in a UK city’, Addiction Research 8 (1), pp. 5–26.
Nencini, P., Ahmed, A. M. and Elm I, A. S. (1986) ‘Subjective effects of khat chewing in humans’, Drug and Alcohol Dependence 18 (1), pp. 97–105.
Nencini, P., Grassi, M.C., Botan, A. A., Asseyr, A. F. and Paroli, E. (1989) ‘Khat chewing spread to the Somali community in Rome’, Drug and Alcohol Dependence 23 (3), pp. 255–258.
Patel, N. B. (2000) ‘Mechanism of action of cathinone: the active ingredient of khat (Catha edulis)’, East African Medical Journal 77 (6), pp. 329–332.
Patel, S. L., Wright, S. and Gammampila, A. (2008) ‘Khat use among Somalis in four English cities’, Drugs: Education, Prevention and Policy 15, pp. 37–53.
Patel, S. L. and Murray, R. (2005) ‘Khat use among Somalis in four English cities’, Home Office Findings No. 266, Home Office, London. Available at: http://www.homeoffice.gov.uk/rds/pdfs05/r266.pdf.
Pennings, E. J. M., Opperhuizen, A. and van Amsterdam, J.G.C. (2008) ‘Risk assessment of khat use in the Netherlands: a review based on adverse health effects, prevalence, criminal involvement and public order’, Regulatory Toxicology and Pharmacology 52 (3), pp. 199–207.
Schechter, M. D. (1990) ‘Dopaminergic nature of acute cathine tolerance’, Pharmacology Biochemistry and Behavior 36 (4), pp. 817–820.
Szendrei, K. (1980) ‘The chemistry of khat’, Bulletin of Narcotics 32 (3), pp. 5–35.
Toennes, S. W. and Kauert, G. F. (2004) ‘Driving under the influence of khat: alkaloid concentrations and observations in forensic cases’, Forensic Science International 140 (1), pp. 85–90.
Toennes, S. W., Harder, S., Schramm, M., Niess, C. and Kauert, G. F. (2003) ‘Pharmacokinetics of cathinone, cathine and norephedrine after the chewing of khat leaves’, British Journal of Clinical Pharmacology 56 (1), pp. 125–130.
Turning Point (2004) Khat use in Somali, Ethiopian and Yemeni communities in England: issues and solutions, Home Office, London. Available at: http://drugs.homeoffice.gov.uk/publication-search/diversity/khat-use-report2835.pdf?view=Binary.
Widler, P., Mathys, K., Brenneisen, R., Kalix, P. and Fisch, H. U. (1994) ‘Pharmacodynamics and pharmacokinetics of khat: a controlled study’, Clinical Pharmacology and Therapeutics 55 (5), pp. 556–562.
World Health Organization (2006) Assessment of khat (Catha edulis Forsk), 34th Meeting, Expert Committee on Drug Dependence. Available at: http://www.who.int/medicines/areas/quality_safety/4.4KhatCritReview.pdf.
World Health Organization Expert Committee on Drug Dependence (2006) 34th report (no. 942). WHO, Geneva. Available at: http://whqlibdoc.who.int/trs/WHO TRS 942 eng.pdf.