Pharmacological Aspects of Chewing the Qat Leaves (Part 1) [Archives:2000/32/Health]

August 7 2000

In certain parts of eastern Africa and southern Arabia, the stimulating properties of the leaves of the Khat bush were probably known before those of coffee (55), and the habit of Khat chewing has been common on those areas for many centuries. The effects of Khat were reported in the literature as early as 1237 by the Arabian physician Naguib Ad Din (87), who proposed the use of Khat for the treatment of depressive states, and by other writers of the same period who reported that it was effective in blunting the sensations of hunger and fatigue (82,87).
Since the Khat leaf rapidly loses it s effect upon wilting, the Khat habit has remained, until recently, endemic to the areas where the plant was grown. During the last decades, however, due to the development of road networks and the availability of air transport, the habit has spread considerably in those regions and to countries where the plant does not grow. Thus, shipments of Khat have even been observed by customs authorities in France, Great Britain, and the United States.
The growing use of Khat has motivated an interest in further knowledge of its active ingredients and their pharmacological effects. A number of studies have therefore been made in an attempt to throw light on these problems. The investigations led to the discovery of the alkaloid (-) cathinone, which is now considered to be the constituent that is mainly responsible for the stimulating properties of Khat leaves. The present review is intended to describe the medical aspects of Khat chewing, to summarize the pharmacological data concerning Khat constituents that have thus far been reported in the literature and to provide some background information.
The Habit of Chewing Khat:
In some countries where the use of Khat is widespread, the habit has a deep-rooted social and cultural tradition (78, 82, 114a, 121a). This is particularly true for Yemen, where many houses have a room called a muffraj that is specially arranged for regular sessions of Khat chewing. In the Yemen Arab Republic, more than 4% of the arable land is used for Khat cultivation (115); the bush grows on moist slopes at altitudes of 3000 to 8000 ft, and it is quite adaptable to varying ecological conditions (83, 115). The first Khat crop is ready for harvesting 3 to 5 yrs after planting and, although there are marked seasonal differences in regrowth, Khat can be harvested throughout the year. The shoots at the tips of the branches are cut in the early hours of the day, bundled, and then usually wrapped in banana leaves to preserve their freshness. The material is then speedily transported to the markets, where it is sold by late morning. The buyers selects from among various types of Khat available, which also vary considerably in price, the most expensive (because the most potent) material being, in general, the freshest and that with the youngest leaves.
For the consumption of Khat in the traditional social setting, the chewers meet in a house some time after noon, usually bringing their own supply. After being welcomed and carefully seated according to their social position, the guests begin to masticate the leaves thoroughly one by one. The juice is swallowed, while the residue of the leaves is stored in the cheek as a bolus of macerated material for further extraction, and is finally ejected. Altogether, each person takes some 1000 to 200g of the leaves; young leaves are most favored, mainly because they are more potent but also because they are tenderer to chew. During the session, the group may smoke from water pipes, and there is a generous supply of beverages (65,89). After the Khat leaves have been chewed, the guests stay on for most of the afternoon, passing their time in animated discussions often devoted to matters of general interest, such as community affairs. From this point of view, Khat can be seen as a factor furthering interaction and structuring social life. The Khat session also plays an important role at weddings and other family events (121a). Khat is frequently used during work by craftsmen, laborers, and especially by farmers, in order to reduce physical fatigue (83). Besides these traditional forms of consumption, Khat is nowadays also chewed by single individuals idling in the streets, particularly in towns and cities where it has been introduced within the last decades. In these regions, Khat is also consumed (sometimes along with alcoholic beverages and other drugs) at gatherings which lack the restraint and well-defined social setting described above. The social aspects of Khat use are discussed extensively in the publications of Hughes (65), Kennedy et al. (78), Nelhans (102), and Schopen (121a)
To be continued next issue