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Use.

Khat leaves can be made into a tea, but generally they are chewed for their stimulating effect. They are thoroughly masticated one by one; the juice is swallowed while their residue is stored in the cheek and later ejected. Young leaves are the most tender and potent; the leaves must be fresh to be effective. A portion is about 100 to 200 grams of leaves; they are predominantly consumed in a social setting. In Yemen, the habit is part of the cultural tradition and of great importance to social life; many houses have a room specifically arranged for the khat session, for which men meet almost every day. During the session, the group may also smoke from a water-pipe, and there is a supply of beverages. Khat use by women is less formal and much less frequent. In East Africa, khat use is more recreational in nature, with the leaves being consumed at times together with ALCOHOL or other drugs. There is also a tradition of khat use by farmers and craftspeople, who chew it to enhance work performance and to stay alert.

Khat consumption has increased significantly during recent decades; it has been estimated that at present about 5 million portions per day are consumed. Although use is limited to the region where it grows, khat is now also exported by air to Europe and North America, where it is sold mainly to immigrants from Yemen and East Africa.

Effects.

The pharmacology of khat has been reviewed and its effects are characterized by a moderate degree of central nervous system (CNS) stimulation, resulting in a state of mild euphoria and excitement, often accompanied by talkativeness to excess. High doses may induce restlessness and sometimes manic behavior. Excessive consumption may lead to toxic psychosis. Khat produces ANOREXIA (loss of appetite) and constipation; it has sympathomimetic effects on the cardiovascular system. Dilation of the pupil and staring are indicative of the acute effect of khat. Habitual chewing is usually revealed by a brownish staining of the teeth.

The effects are very similar to those of AMPHETAMINE, and the difference between the two drugs is quantitative rather than qualitative. Accordingly, habitual khat use may give rise to psychic dependence, which usually is moderate but often persistent. The withdrawal symptoms after prolonged use are slight trembling, lethargy, mild depression, and recurrent bad dreams. Khat use by the habitué is often compulsive, with the necessary supplies obtained at least once a day, even at the expense of vital needs; in the countries where khat use is widespread, the socioeconomic consequences of the habit are considerable.

Constituents.

Khat contains the alkaloids norephedrine, cathine, and cathinone (see Figure 2). Norephedrine and cathine do not contribute significantly to the psychostimulant action, however, they are probably of importance for the sympathomimetic effects (on the autonomic nervous system). The constituent that is mainly responsible for the stimulant qualities and the dependence-producing effects of khat is cathinone. This ALKALOID must be considered a natural amphetamine, since the two substances have the same mechanism of action. However, cathinone has a half-life of only 1.5 hours, whereas that of amphetamine is much longer. Since cathinone is absorbed gradually from the leaves during chewing and is inactivated in the body rather rapidly, the pharmacological effects of khat are usually limited.

(SEE ALSO: Amphetamine)

PETER KALIX