Alterations of Gefitinib Pharmacokinetics by Co-administration of Herbal Medications in Rats

Objective： To evaluate the potential pharmacokinetic interactions of the anticancer agent gefitinib （Iressae） and the oriental medications Guipi Decoction （归脾汤, GPD, Guibi-tang in Korean） and Bawu Decoction （八物汤, BWD, Palmul-tang in Korean）. Methods： Methylceliulose （MC, control）, GPD （1,200 mg/kg）, or BWD （6,000 mg/kg） was orally administered to rats either as a single dose or multiple doses prior to gefitinib administration. To examine the effects of a single dose of the herbal medicines, gefitinib （10 mg/kg） was orally administered after 5 min or 1 h of MC or the herbal medicine pretreatments. To examine the effects of the multiple doses of the herbal medicines, gefltinib （10 mg/kg） was orally administered following 7 consecutive days of the administration of MC or each herbal medicine. The plasma concentrations of gefitinib were determined with liquid chromatography-tandem mass spectrometry assay. The plasma concentration-time profiles of gefitinib were analyzed with a noncompartmental analysis. Results： Gefitinib was rapidly absorbed and showed a mono- exponential decline with an elimination half-life of 3.7-4.1 h. The pharmacokinetics of gefitinib was not affected by GPD pretreatment. However, a significantly lower maximum plasma concentration （Crux, P〈0.05） and area under the curve （P〈0.05）, and a delayed time to reach Cmax （Tmax, P〈0.01） were observed in both single- and multiple- dose BWD-pretreated rats compared with the control rats. Conclusions： BWD and not GPD might delay and interfere with gefitinib absorption. Further evaluations of the clinical significance of these findings are needed.