Alterations of Gefitinib Pharmacokinetics by Co-administration of Herbal Medications in Rats / 中国结合医学杂志

<p><b>OBJECTIVE</b>To evaluate the potential pharmacokinetic interactions of the anticancer agent gefitinib (Iressa®) and the oriental medications Guipi Decoction (, GPD, Guibi-tang in Korean) and Bawu Decoction (, BWD, Palmul-tang in Korean).</p><p><b>METHODS</b>Methylcellulose (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, gefitinib (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.</p><p><b>RESULTS</b>Gefitinib was rapidly absorbed and showed a monoexponential 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 (C, P<0.05) and area under the curve (P<0.05), and a delayed time to reach C (T, P<0.01) were observed in both single- and multipledose BWD-pretreated rats compared with the control rats.</p><p><b>CONCLUSIONS</b>BWD and not GPD might delay and interfere with gefitinib absorption. Further evaluations of the clinical significance of these findings are needed.</p>

Effects of traditional herbal formulae on human CYP450 isozymes / 中国结合医学杂志

<p><b>OBJECTIVE</b>To assess the effects of traditional herbal formulae Sijunzi Decoction (, Sagunja-tang, SJZD), Siwu Decoction (, Samul-tang, SWD), Bawu Decoction (, Palmul-tang, BWD) and Shiquan Dabu Decoction (, Sipjeondaebo-tang, SDD) on the activities of human cytochrome P450 (CYP450), a drug-metabolizing enzyme.</p><p><b>METHODS</b>Herbal formula water extracts were filtered and lyophilized after the powder extracts were dissolved in distilled water. The activities of major human CYP450 isozymes (CYP3A4, CYP2C19, CYP2D6 and CYP2E1) were measured using in vitro fluorescence-based enzyme assays. The inhibitory effects of the herbal formulas on the activities of CYP450 were characterized as half maximal inhibition concentration (IC) values.</p><p><b>RESULTS</b>All the tested herbal formulae inhibited CYP2C19 activity (IC: SJZD, 83.28 μg/mL; SWD, 235.54 μg/mL; BWD, 166.82 μg/mL; SDD, 178.19 μg/mL); SJZD (IC= 196.46 μg/mL), SWD (IC= 333.42 μg/mL) and SDD (IC= 163.42 μg/mL) inhibited CYP2E1-mediated metabolism; whereas BWD exhibited comparatively weak inhibition of CYP2E1 (IC= 501.78 μg/mL). None of the four herbal formulas significantly affected CYP3A4 or CYP2D6.</p><p><b>CONCLUSIONS</b>These results suggest that SJZD, SWD, BWD and SDD could potentially inhibit the metabolism of co-administered synthetic drugs whose primary route of elimination is via CYP2C19. In addition, clinically relevant pharmacokinetic interactions could occur when SJZD, SWD or SDD is co-administered with drugs metabolized by CYP2E1. Our findings provide information for the safety and effective clinical use of these four classic herbal formulas.</p>