Interactions Between Herbal Medicines and Prescribed Drugs. An Updated Systematic Review

Department of Experimental Pharmacology, University of Naples Federico II, via D Montesano 49, Naples 80131, Italy.
Drugs (Impact Factor: 4.34). 02/2009; 69(13):1777-98. DOI: 10.2165/11317010-000000000-00000
Source: PubMed


The concomitant use of herbal medicines and pharmacotherapy is wide spread. We have reviewed the literature to determine the possible interactions between seven popular herbal medicines (ginkgo, St John’s wort, ginseng, garlic, echinacea, saw palmetto and kava) and conventional drugs. Literature searches were performed using MEDLINE, Cochrane Library and EMBASE and we identified 128 case reports or case series, and 80 clinical trials.

Clinical trials indicate that St John’s wort (Hypericum perforatum), via cytochrome P450 (CYP) and/or P-glycoprotein induction, reduces the plasma concentrations (and/or increases the clearance) of alprazolam, amitriptyline, atorvastatin, chlorzoxazone, ciclosporin, debrisoquine, digoxin, erythromycin, fexofenadine, gliclazide, imatinib, indinavir, irinotecan, ivabradine, mephenytoin, methadone, midazolam, nifedipine, omeprazole, oral contraceptives, quazepam, simvastatin, tacrolimus, talinolol, verapamil, voriconazole and warfarin. Case reports or case series suggest interactions of St John’s wort with adrenergic vasopressors, anaesthetics, bupropion, buspirone, ciclosporin, eletriptan, loperamide, nefazodone, nevirapine, oral contraceptives, paroxetine, phenprocoumon, prednisone, sertraline, tacrolimus, theophylline, tibolone, tryptophan, venlafaxine and warfarin. Ginkgo (Ginkgo biloba) decreases the plasma concentrations of omeprazole, ritonavir and tolbutamide. Clinical cases indicate interactions of ginkgo with antiepileptics, aspirin (acetylsalicylic acid), diuretics, ibuprofen, risperidone, rofecoxib, trazodone and warfarin. Ginseng (Panax ginseng) may interact with phenelzine and warfarin. Kava (Piper methysticum) increases the clearance of chlorzoxazone (a CYP2E1 substrate) and may interact with alprazolam, levodopa and paroxetine. Garlic (Allium sativum) interacts with chlorpropamide, fluindione, ritonavir and warfarin; it also reduces plasma concentrations of chlorzoxazone (a CYP2E1 probe). Echinacea might affect the clearance of caffeine (a CYP1A2 probe) and midazolam (a CYP3A4 probe). No interactions have been reported for saw palmetto (Serenoa repens.)

Numerous interactions between herbal medicines and conventional drugs have been documented. While the significance of many interactions is uncertain, several interactions, particularly those with St John’s wort, may have serious clinical consequences.


Available from: Angelo Izzo, Mar 22, 2016
    • "Other relevant factors not recorded that could have contributed to the development of allergy-like reactions could be the patient's genetics, nutrition status, concurrent medication, disease states (e.g., food allergies) as well as exercise-induced anaphylaxis [37, 40]. Also, unrecognized herbal–drug interactions could result in a lack of allergy control and the manifestation of allergy symptoms [41]. The strengths of our study design include the international collection of reports from 42 countries over more than four decades as well as the use of standardized HATC drug classification, WHO-ART nomenclature, and formal causality assessment for adverse reactions. "
    [Show abstract] [Hide abstract] ABSTRACT: Introduction Herbal medicines are used worldwide and with an increasing popularity in Western countries. Although often perceived as ‘naturally safe’, herbals may cause severe adverse drug reactions (ADRs), with immediate allergic reactions being particularly life threatening. Objectives The aim of this study was to analyse immediate allergy-like ADRs to herbals documented in VigiBase®, the WHO international pharmacovigilance database. Methods The documentation of all suspected ADRs in association with herbal exposure reported to VigiBase® from 1969 to August 2014 was retrieved. Among all reports in which WHO-ART reaction terms were indicative of acute allergic reactions, those classified as ‘suspect’ with a documented causality assessment and latency time of ≤1 day were selected. For the most frequent specific herbal–ADR combinations, the information component (IC) as a measure of disproportionality based on Bayesian statistics was calculated. Results We identified 757 reports out of 1039 ADRs. Products with mixed herbals (36.0 %) as well as those administered orally (63.2 %) were predominant. The most frequent reactions were urticaria and rash (49.2 %). Anaphylactic reactions accounted for 9.5 %. Disproportionally frequent reporting of mouth edema (IC = 1.81) and anaphylactic reactions (IC = 1.24) to Phleum pretense were noted. Conclusion Our findings indicate that herbal medicines for oral use carry a risk of causing immediate allergy-like ADRs. Studies using the Vigibase® database can identify specific combinations of particular herbs and adverse reactions. Healthcare professionals and patients should be aware of these risks and report any serious adverse experiences.
    No preview · Article · Mar 2016 · Drug Safety
    • "On the one hand, this type of co-existence can assure the maintenance of traditional and non-traditional knowledge on natural resources at the same time that allows the access to modern official health facilities, amplifying therapeutic options (see [22]). On the other hand, integration between different medical systems must be carefully evaluated in terms of implications to public health and caution must be taken as some interactions between CAM and OM products can be harmful and have serious clinical consequences [23,24]. Under contexts of medical pluralism, the joint use of different resources can help disseminate maladaptive behaviors. "
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    No preview · Article · Mar 2016 · European Journal of Integrative Medicine
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    • "The probe drugs were selected in accordance with existing studies, such as a Pittsburgh cocktail study[11], a Cooperstown cocktail study[12]and an Inje cocktail study[13]. Many natural materials can affect efflux proteins such as P-gp[14], even though conventional cocktail combinations do not include a drug that probes for this protein. To assess CYP enzyme activity, the present approach incorporated the cocktail combination of the Inje study, a previous drug interaction study that used a cocktail technique to evaluate general drug interactions by calculating metabolic ratios for a probe and its metabolite in plasma at certain time points. "
    [Show abstract] [Hide abstract] ABSTRACT: We evaluated the drug interaction profile of Red Ginseng (RG) with respect to the activities of major cytochrome P450 (CYP) enzymes and the drug transporter P-glycoprotein (P-gp) in healthy Korean volunteers.
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