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

Effect of Single-Dose and Short-Term Administration of Si Jun Zi Tang on the Pharmacokinetics of Gefitinib in Rats

Background

Si Jun Zi Tang (SJZ), a four-herb Chinese medicine formula that has been described for approximately one thousand years, is often prescribed for cancer patients as a complementary therapy in China. However, the mechanism by which Si Jun Zi Tang enhances the efficacy of gefitinib is unclear.

Methods

We investigated how Si Jun Zi Tang affected the pharmacokinetics of gefitinib in rats. A rapid, specific, and reliable ultra-performance liquid chromatography method with mass spectrometry was established to determine the plasma concentration of gefitinib.

Results

The results showed that a single intragastrically administered dose of Si Jun Zi Tang increased the pharmacokinetic parameters of gefitinib (C _max, 3156.13 μg/L; A UC, 46281.5 μg/L/h) by 3 folds in rats compared with the administration of gefitinib alone (C _max, 1352.07 μg/L; AUC, 11823.7 μg/L/h). Si Jun Zi Tang could also alter the pharmacokinetics of gefitinib by prolonging the time to reach C _max.

Conclusions

Potential pharmacokinetic interactions between gefitinib and SJZ were evaluated, and SJZ extended T _max and T1/2 and increased the C _max and AUC of gefitinib. Long-term administration of gefitinib in combination with Si Jun Zi Tang would improve the efficacy of gefitinib.

Clinical implications of food-drug interactions with small-molecule kinase inhibitors

During the past two decades, small-molecule kinase inhibitors have proven to be valuable in the treatment of solid and haematological tumours. However, because of their oral administration, the intrapatient and interpatient exposure to small-molecule kinase inhibitors (SMKIs) is highly variable and is affected by many factors, such as concomitant use of food and herbs. Food-drug interactions are capable of altering the systemic bioavailability and pharmacokinetics of these drugs. The most important mechanisms underlying food-drug interactions are gastrointestinal drug absorption and hepatic metabolism through cytochrome P450 isoenzymes. As food-drug interactions can lead to therapy failure or severe toxicity, knowledge of these interactions is essential. This Review provides a comprehensive overview of published studies involving food-drug interactions and herb-drug interactions for all registered SMKIs up to Oct 1, 2019. We critically discuss US Food and Drug Administration (FDA) and European Medicines Agency (EMA) guidelines concerning food-drug interactions and offer clear recommendations for their management in clinical practice.