Khat, a Cultural Chewing Drug: A Toxicokinetic and Toxicodynamic Summary

Abstract

Khat (Catha edulis) is a recreational, chewed herbal drug that has been used as a psychostimulant for centuries in East Africa and the Arabian Peninsula, namely in Somalia, Ethiopia, and Yemen. However, the growing worldwide availability of khat has produced widespread concern. The plant comprises a large number of active substances, among which cathinone, cathine, and norephedrine are the main constituents, which can be included in the group of sympathomimetics of natural origin. In fact, these compounds are amphetamine analogues, and, as such, they have amphetamine-like nervous system stimulant effects. Chewing the leaves gives people a sensation of well-being and increases energy, alertness, and self-confidence. The chronic use of khat is, however, associated with severe cardiac, neurological, psychological, and gastrointestinal complications. The psychological dependence and withdrawal symptoms of khat are the reasons for its prolonged use. The aim of this paper is to review current knowledge on the khat plant with toxicokinetic and toxicodynamic perspectives. Namely, this review paper addresses in vitro, in vivo, and human studies. The models used, as well as the concentrations and doses with the respective biological effects, are discussed. Additionally, the main drug interactions involved with khat are described.

Keywords: amphetamine-like; cathine; cathinone; kinetics; norpseudoephedrine; toxicology.

Figure 1

Chemical structures of cathinone, cathine (norpseudoephedrine), noradrenaline, norephedrine, and amphetamine. Structural differences to amphetamine are underlined (blue) in the other compounds.

Figure 2

Historical sequence of the countries in which khat became a controlled substance.

Figure 3

Stereoselective cathinone metabolism and the main metabolites excreted in urine (adapted from [24,25]).

Figure 4

Mechanism of toxicity of cathinone on the central nervous system. (a) Dopamine release induction, (b) MAO inhibition in neurons and astrocytes.

Figure 5

Common adverse effects of khat abuse [1,3,26,51].