REVIEW ARTICLE Khat: Pharmacological and Medical Aspects and its Social Use in Yemen Ahmed Al-Motarreb, Kathryn Baker and Kenneth J Broadley* Department of Pharmacology, Welsh School of Pharmacy, Cardiff University, Cathays Park, Cardiff CF10 3XF, UK Fresh leaves of the khat tree (Catha edulis Forsk.) are chewed for their euphoric properties in East Afri- ca and parts of the Middle East, such as The Yemen. This review describes the history, cultivation and constituents of khat, and the social aspects of khat chewing in Yemen. The major pharmacologically active constituent of the fresh leaves is ()-S-cathinone. The pharmacology of ()-S-cathinone in the cen- tral nervous system and the peripheral effects are described. ()-S-Cathinone is regarded as an ampheta- mine-like sympathomimetic amine and this mechanism of action is discussed in relation to the central stimulant actions and the cardiovascular effects of increasing blood pressure and heart rate. The risk factors associated with khat chewing are described, with emphasis on the reported increased incidence of acute myocardial infarction. Copyright # 2002 John Wiley & Sons, Ltd. Keywords: khat; ()-S-cathinone; acute myocardial infarction; risk factors. INTRODUCTION The chewing of khat (or qat) leaves (Catha edulis Forsk.) is widely practised in East Africa and parts of the Middle East, such as The Yemen where it forms a deep-rooted social and cultural function (Drake, 1988). This habit has now spread to ethnic communities in the rest of the World, including Britain such as the Somali Commu- nities in South Wales and London (Griffiths, 1998). The pleasure derived from khat chewing is attributed to the euphoric actions of its content of ()-S-cathinone, a sympathomimetic amine with properties described as similar to those of amphetamine (Kalix and Braenden, 1985; Kalix, 1988, 1992). Although ()-S-cathinone is restricted under international convention and in the UK under the Misuse of Drugs Act 1971, khat is not controlled and its possession and use are not restricted in the UK (Griffiths, 1998). THE ORIGIN OF THE KHAT PLANT The khat tree was first described by Peter Forskal (1736- 1763), a Swedish botanist who had travelled with his friend the geographer Karsten Niebuhr (1736-1815) on an expedition to Egypt and Yemen organized by King Friederick V of Denmark (Raman, 1983). Among the many things collected was khat, which Forskal described as Catha edulis in the family Celastraceae. Karsten Niebuhr was the only survivor of the five members of the expedition and in memory of his friend, he called khat Catha edulis Forskal; this was published in the botanical papers in 1775 (Raman, 1983). Most researchers believe that khat originates from Ethiopia. Although it has grown for centuries in Yemen, there is no certainty of the date for its introduction (Al- Radee, 1992). One opinion is that khat was introduced to Yemen during the Ethiopian occupation of Yemen in 525 AD, when it was limited to the invaders. However, this date is believed by others to be too early as Abu Al-Hasan Al-Hamdani in the 10th century (945 AD) does not mention khat in his botanical treatise on the many plants he described. The view that khat came to Yemen at the beginning of the 13th century is supported by a letter written by a religious scholar, Ahmed Ben Alwan, asking the ruler at that time to legally ban the habit of khat chewing because it prevented Yemenis from performing their prayer, especially the afternoon (Asr) and sunset (Maghreb) prayer periods. The first report of khat as a medicine was by the Arabian physician Abu Al-Rihan Bin Ahmed Al-Baironi (973-1051 AD) in his book Pharmacy and Therapeutic Art (El-Tahir, 1990). Khat is also mentioned in an Arabic medical book The Complex Drugs which was written in 1237 AD. The author, Najeeb Al-Deen Al-Samargandi, described khat as a treatment for depression, because it led to happiness and excitement (Al-Attas, 1981). The historian Ibn Fadl Allah Al-Amri (1301-1348 AD) mentioned khat in the events of the war between Sabr Al- Deen (the King of Ifat) and the King of Ethiopia (Emdasyoon). In the excitement of his victory, King Sabr Al-Deen swore to demolish the residence of the Ethiopian king (Marade) and to plant khat in its place (Al-Attas, 1981). In view of the above considerations, the consensus of opinion is that khat was probably introduced into Yemen as a social habit in the 13th century. THE KHAT TREE: CULTIVATION IN YEMEN The khat tree is a perennial green plant (Fig. 1) which is PHYTOTHERAPY RESEARCH Phytother. Res. 16, 403–413 (2002) Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ptr.1106 Copyright # 2002 John Wiley & Sons, Ltd. * Correspondence to: Dr K. J. Broadley, Department of Pharmacology, Welsh School of Pharmacy, Cardiff University, Cathays Park, Cardiff CF10 3XF, UK. E-mail: BroadleyKJ@Cardiff.ac.uk Received 10 October 2001 Revised 30 April 2002 Accepted 14 May 2002