Acta Pharm. 49 (1999) 43–50
Khat, the fresh leaves of Catha edulis, Celastracoeae, is widely employed in some countries, particularly in Yemen and Somalia, for chewing and its misuse has been recently surveyed by World Health Organisation (WHO). The leaves contain cathinone, which is considered responsible for the amphetamine-like stimulant effect of the plant. Bioavailability of amoxycillin was examined in eight healthy adult male volunteers by monitoring their urinary drug excretion. Amoxycillin was administered in single doses of 500 mg. On different occasions, each volunteer received amoxycillin alone, before, after or during khat chewing. Khat chewing time was restricted to the four-hour period. The results indicated that the extent of amoxycillin absorption was significantly reduced in case of drug administration during khat chewing only. The reduction of amoxycillin bioavailability produced by khat might be attributed to some forms of khat-drug interactions, mediated through the possible complex formation with tannins, the adstringent action of tannins on mucous membranes of gastrointestinal tract (GIT), and the effect of ascorbic acid content on the ionization behaviour of the drug or on pH favourable for optimum absorption. The effect could be also attributed to the possible khat effect on the blood flow of body organs. The results of the study point out the need for regimen or dose adjustment for khat-chewing people who receive therapy, as exemplified by amoxycillin.
Keywords: amoxycillin, bioavailability, khat, chewing