Pharmacokinetic properties, potential herb-drug interactions and acute toxicity of oral Rhizoma coptidis alkaloids.

INTRODUCTION: Rhizoma coptidis shows various pharmacological activities attributed to its alkaloid constituents. To guide the pharmacological studies, the candidate drug research and development and the clinic applications of these compounds, a review on their pharmacokinetic behavior and toxicity should be beneficial. AREAS COVERED: This article looks at the pharmacokinetic properties and potential herb-drug interactions found with Rhizoma coptidis alkaloids. Furthermore, the article also reviews the acute toxicity of these alkaloids. EXPERT OPINION: Generally, the systemic exposures of the alkaloids are extremely low after oral administration. The alkaloids may present their systemic activities via generated metabolites and/or the tissue distributed alkaloids themselves, or by modulating effectors in the gut. The drug transporters and drug-metabolizing enzymes involved in the in vivo process, the modulatory effects on both P-glycoprotein and cytochrome P450 isoenzymes and the acute toxicity of the alkaloids were all well documented. However, first, since very significant difference exists between the blood and tissue exposure, to find suitable pharmacokinetic markers of the alkaloids in blood may be challenging but necessary. Second, the dose-systemic exposure-response relationships of the alkaloids should also be determined. Third, in order to improve the oral bioavailability and efficacy, it is important to design derivatives or formulations of the alkaloids with better pharmacokinetic features.