Herb–drug interaction has become a serious problem since herbal medicine is extensively used in the
modern world. This study investigates effects of Andrographis paniculata extract (APE) and its major component,
andrographolide (AG), on the pharmacokinetics of theophylline, a typical substrate of cytochrome
P450 1A2 enzyme, in rats. After APE or AG pretreatment for 3 days