Curcuminoid drug interactions

Peer-reviewed | Manuscript received: May 17, 2015 | Revision accepted: August 17, 2015

Older and chronically ill people often attempt to improve their health by taking food supplements. Thus they often take drugs together with plant extracts that might influence the effects of these drugs. In the present article, we describe the evidence for drug interactions involving the secondary plant metabolite curcumin and the related curcumioids.

Introduction

Curcuminoids are lipiphilic secondary plant metabolites isolated from the roots of the plant Curcuma longa (turmeric) (=> see Schiborr et al., page M636 [1]) and consist of ca. 77 % curcumin, 17 % demethoxycurcumin and 6 % bis-demethoxycurcumin [2]. Because of their many health supporting activities, they have long been used in traditional Chinese medicine for the treatment of respiratory disease, anorexia, diabetic wounds or for digestive disorders [3]. Curcumin supplements are freely commercially available, mostly as capsules or tablets; many people take them to improve their health. The oral bioavailability of curcumin is low, i.e. it is poorly absorbed, and rapidly metabolized and eliminated. For this reason, curcumin formulations with better bioavailability are being sold increasingly often; these give much higher plasma concentrations of curcumin than native curcumin [1].

Summary

The secondary plant metabolite curcumin and the related curcuminoids may be valuable in the prevention and treatment of many different degenerative diseases. As curcuminoids are often taken as supplements by some population groups, it may be asked whether this can lead to changes in the pharmacokinetics or pharmacodynamics of other drugs taken at the same time. It is particularly important to clarify this issue, as native curcumin only exhibits low bioavailability, but many novel formulations are being developed that enhance its absorption in the small intestine and thus lead to higher concentrations of the active drug. Cell culture and animal studies have shown that native curcumin can affect xenobiotic metabolizing enzymes. There are also effects on the pharmacokinetics of active substances in animal studies and in men. On the other hand, it has not been shown that curcumin has any adverse effects on the pharmacological activity of other drugs. However, it must be emphasized that these studies are preliminary rather than conclusive and must be supported by larger scale investigations. It has also not been investigated whether the formulations with better bioavailability can influence the pharmacokinetics of other drugs.

Keywords: curcumin, curcuminoids, turmeric, drug interactions, safety, drug

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