Chewing khat reduces the absorption of
ampicillin, and to a lesser extent
amoxicillin, but the effects are minimal 2 hours after khat chewing stops.
Khat (the leaves and stem tips of Catha edulis) is chewed in some African and Arabian countries for its stimulatory properties. The authors of one of the studies concluded that both
ampicillin and
amoxicillin should be taken 2 hours after khat chewing to ensure that maximum absorption occurs.