A critical evaluation of drug interactions with Echinacea spp.

Abstract

Accurate information concerning drug-herb interactions is vital for both healthcare providers and patients. Unfortunately, many of the reviews on drug-herb interactions contain overstated or inaccurate information. To provide accurate information on drug-herb interactions healthcare providers must account for product verification, dosage, medicinal plant species, and plant part used. This critical review assessed the occurrence of drug interactions with one of the top selling botanical remedies, echinacea including Echinacea angustifolia, E. pallida, and E. purpurea. Only eight papers containing primary data relating to drug interactions were identified. Herbal remedies made from E. purpurea appear to have a low potential to generate cytochrome P450 (CYP 450) drug-herb interactions including CYP 450 1A2 (CYP1A2) and CYP 450 3A4 (CYP3A4). Currently there are no verifiable reports of drug-herb interactions with any echinacea product. However, further pharmacokinetic testing is necessary before conclusive statements can be made about echinacea drug-herb interactions. Given our findings, the estimated risk of taking echinacea products (1 in 100,000), the number of echinacea doses consumed yearly (> 10 million), the number of adverse events (< 100) and that the majority of use is short term, E. purpurea products (roots and/or aerial parts) do not appear to be a risk to consumers.

Interactions of antioxidants isolated from tart cherry (Prunus cerasus) fruits

“…Yet, the combined bioactivity of the mixture is potentiated when the interaction results in improved solubility, absorption, safety, stability, or bioavailability of the active principles (Boik, Newman, & Boik, 2008;Freeman & Spelman, 2008;Greco, Bravo, & Parsons, 1995;Liu, 2003;Spinella, 2002). Negative interactions (interferences) may also occur when certain components of the mixture inhibit the full biological activity of pharmacologically-active compounds by reducing their stability or bioavailability or by enhancing their metabolism.…”

Use of Complementary Medicines by Cardiac Surgery Patients; Undisclosed and Undetected

“…Currently, the evidence suggesting echinacea may induce pharmacokinetic interactions with cytochrome 3A substrates such as midazolam is unclear as some research indicates a modest induction effect whereas other studies show no effect. It is suspected that the inconsistent results relate to differences in chemical composition between echinacea extracts and if a pharmacokinetic interaction occurs, it is likely to be subtle [43][44][45].…”

The Medicinal Chemistry of Echinacea Species

“…The possible side effects, toxicity , frequency and type of adverse events, allergic reactions, and toxicology, together with contraindications and warnings of interactions and pregnancy and lactation were reviewed case by case based on clinical data reported before 2005 (Barnes et al 2005 ). Despite some drug interaction concerns, the overall agreement is that Echinacea is one of the safest herbal medicines with few reports of adverse effects (Mills and Bone 2005 ;Freeman and Spelman 2008 ). Additional discussion of safety, allergic reactions, and drug herb interactions are discussed in the Research on Echinacea Use in Western Medicine chapter .…”