Kava--the unfolding story: report on a work-in-progress

Safety Aspects of Herb Interactions: Current Understanding and Future Prospects

BACKGROUND

The use of herbal medicines is on the rise throughout the world due to their perceived safety profile. However, incidences of herb-drug, herb-herb and herb-food interactions considering safety aspects have opened new arenas for discussion.

OBJECTIVE

The current study aims to provide comprehensive insights into the various types of herb interactions, the mechanisms involved, their assessment, and historical developments, keeping herbal safety at the central point of discussion.

METHODS

The authors undertook a focused/targeted literature review and collected data from various databases, including Science Direct, Wiley Online Library, Springer, PubMed, and Google Scholar. Conventional literature on herbal remedies, such as those by the WHO and other international or national organizations.

RESULTS

The article considered reviewing the regulations, interaction mechanisms, and detection of herb-herb, herb-drug and herb-food interactions in commonly used yet vital plants, including Glycyrrhiza glabra, Mentha piperita, Aloe barbadensis, Zingiber officinale, Gingko biloba, Withania somnifera, etc. The study found that healthcare professionals worry about patients not informing them about their herbal prescriptions (primarily used with conventional treatment), which can cause herb-drug/herb-food/herb-herb interactions. These interactions were caused by altered pharmacodynamic and pharmacokinetic processes, which might be explained using in-vivo, in-vitro, in-silico, pharmacogenomics, and pharmacogenetics. Nutrivigilance may be the greatest method to monitor herb-food interactions, but its adoption is limited worldwide.

CONCLUSION

This article can serve as a lead for clinicians, guiding them regarding herb-drug, herb-food, and herb-herb interactions induced by commonly consumed plant species. Patients may also be counseled to avoid conventional drugs, botanicals, and foods with a restricted therapeutic window.

Recreational Drugs and the Risk of Hepatocellular Carcinoma

Recreational or aesthetic drug use is a distinctive behavior of humans, principally attested in the last century. It is known that recreational and illegal drugs are major contributors to the universal morbidity rate worldwide. Many of these substances have a well-established hepatotoxic potential, causing acute or chronic liver injury, liver fibrosis and cirrhosis, but their implications for hepatocellular carcinoma or other varieties of liver tumors are little known. In this article, we perform an extensive literature review, aiming to provide updated information about recreational drug use and the risk of developing liver tumors. Khat use and pyrrolizidine alkaloid consumption (present in some natural plants) have been linked to liver cirrhosis. Kava intake is associated with different liver tumors in animal models but not in humans. Cannabis' potential to accelerate liver fibrosis in chronic hepatitis is controversial according to the existing data. Cigarette smoking is an important contributor to hepatocellular carcinoma, and anabolic androgen steroids are well-defined causes of a variety of liver cancers and other hepatic tumors. Long-term follow-up studies of subjects who have developed injuries in association with the use of recreational drugs are warranted so as to better define the risk of developing hepatocellular carcinoma in association with these substances and, thus, to implement health care policies to combat this preventable cause of cancer.

The integrated use of in silico methods for the hepatotoxicity potential of Piper methysticum

Herbal products as supplements and therapeutic intervention have been used for centuries. However, their toxicities are not completely evaluated and the mechanisms are not clearly understood. Dried rhizome of the plant kava (Piper methysticum) is used for its anxiolytic, and sedative effects. The drug is also known for its hepatotoxicity potential. Major constituents of the plant were identified as kavalactones, alkaloids and chalcones in previous studies. Kava hepatotoxicity mechanism and the constituent that causes the toxicity have been debated for decades. In this paper, we illustrated the use of computational tools for the hepatotoxicity of kava constituents. The proposed mechanisms and major constituents that are most probably responsible for the toxicity have been scrutinized. According to the experimental and prediction results, the kava constituents play a substantial role in hepatotoxicity by some means or other via glutathione depletion, CYP inhibition, reactive metabolite formation, mitochondrial toxicity and cyclooxygenase activity. Some of the constituents, which have not been tested yet, were predicted to involve mitochondrial membrane potential, caspase-3 stimulation, and AhR activity. Since Nrf2 activation could be favorable for prevention of hepatotoxicity, we also suggest that these compounds should undergo testing given that they were predicted not to be activating Nrf2. Among the major constituents, alkaloids appear to be the least studied and the least toxic group in general. The outcomes of the study could help to appreciate the mechanisms and to prioritize the kava constituents for further testing.

The protective effects of Kava (Piper Methysticum) constituents in cancers: A systematic review

BACKGROUND

Kava is a beverage made from the ground roots of the plant Piper Methysticum and has long-held a significant place within Pacific island communities. Active compounds were extracted from kava, and secondary metabolites include kavalactones, chalcones, cinnamic acid derivatives and flavanones. It is thought that components of kava may exert an antiproliferative effect through cell cycle arrest and promotion of apoptosis.

METHODS

We conducted a systematic review to summarize available evidence of the anticancer effects of kava components and investigate their potential use for oral squamous cell carcinoma (OSCC) treatment. Eligible studies were identified through a comprehensive search of OVID EMBASE, OVID MEDLINE and Web of Science, as at April 2018.

RESULTS

Of 39 papers that met the inclusion criteria, 32 included in vitro models and 13 included animal studies. A total of 26 different cancers were assessed with 32 studies solely assessing epithelial cancers, 6 mesenchymal cancers and 1 study including both. There was only one report assessing an OSCC cell line. Antiproliferative properties were demonstrated in 32 out of 39 papers. The most researched constituent of kava was flavokavain B followed by flavokavain A. Both were associated with increased expression of pro-apoptotic proteins and decreased expression of anti-apoptotic proteins. Further, they were associated with a dose-dependent reduction of angiogenesis.

CONCLUSION

There was heterogeneity of study models and methods of investigation across the studies identified. Components of kava appear to present an area of interest with chemotherapeutic potential in cancer prevention and treatment, particularly for epithelial neoplasms. To date, there is a paucity of literature of the utility of kava components in the prevention and treatment of oral squamous cell carcinoma.

The direct and highly diastereoselective synthesis of 3,4-epoxy-2-piperidones. Application to the total synthesis and absolute configurational assignment of 3α,4α-epoxy-5β-pipermethystine

The substrate-controlled asymmetric total synthesis and absolute configurational assignment of biologically active 3α,4α-epoxy-5β-pipermethystine is reported.

Herbal Hepatotoxicity: Clinical Characteristics and Listing Compilation

Herb induced liver injury (HILI) and drug induced liver injury (DILI) share the common characteristic of chemical compounds as their causative agents, which were either produced by the plant or synthetic processes. Both, natural and synthetic chemicals are foreign products to the body and need metabolic degradation to be eliminated. During this process, hepatotoxic metabolites may be generated causing liver injury in susceptible patients. There is uncertainty, whether risk factors such as high lipophilicity or high daily and cumulative doses play a pathogenetic role for HILI, as these are under discussion for DILI. It is also often unclear, whether a HILI case has an idiosyncratic or an intrinsic background. Treatment with herbs of Western medicine or traditional Chinese medicine (TCM) rarely causes elevated liver tests (LT). However, HILI can develop to acute liver failure requiring liver transplantation in single cases. HILI is a diagnosis of exclusion, because clinical features of HILI are not specific as they are also found in many other liver diseases unrelated to herbal use. In strikingly increased liver tests signifying severe liver injury, herbal use has to be stopped. To establish HILI as the cause of liver damage, RUCAM (Roussel Uclaf Causality Assessment Method) is a useful tool. Diagnostic problems may emerge when alternative causes were not carefully excluded and the correct therapy is withheld. Future strategies should focus on RUCAM based causality assessment in suspected HILI cases and more regulatory efforts to provide all herbal medicines and herbal dietary supplements used as medicine with strict regulatory surveillance, considering them as herbal drugs and ascertaining an appropriate risk benefit balance.

Hepatotoxicity Induced by "the 3Ks": Kava, Kratom and Khat

The 3Ks (kava, kratom and khat) are herbals that can potentially induce liver injuries. On the one hand, growing controversial data have been reported about the hepatotoxicity of kratom, while, on the other hand, even though kava and khat hepatotoxicity has been investigated, the hepatotoxic effects are still not clear. Chronic recreational use of kratom has been associated with rare instances of acute liver injury. Several studies and case reports have suggested that khat is hepatotoxic, leading to deranged liver enzymes and also histopathological evidence of acute hepatocellular degeneration. Numerous reports of severe hepatotoxicity potentially induced by kava have also been highlighted, both in the USA and Europe. The aim of this review is to focus on the different patterns and the mechanisms of hepatotoxicity induced by “the 3Ks”, while trying to clarify the numerous aspects that still need to be addressed.

Herbal hepatotoxicity in traditional and modern medicine: actual key issues and new encouraging steps

Plants are natural producers of chemical substances, providing potential treatment of human ailments since ancient times. Some herbal chemicals in medicinal plants of traditional and modern medicine carry the risk of herb induced liver injury (HILI) with a severe or potentially lethal clinical course, and the requirement of a liver transplant. Discontinuation of herbal use is mandatory in time when HILI is first suspected as diagnosis. Although, herbal hepatotoxicity is of utmost clinical and regulatory importance, lack of a stringent causality assessment remains a major issue for patients with suspected HILI, while this problem is best overcome by the use of the hepatotoxicity specific CIOMS (Council for International Organizations of Medical Sciences) scale and the evaluation of unintentional reexposure test results. Sixty five different commonly used herbs, herbal drugs, and herbal supplements and 111 different herbs or herbal mixtures of the traditional Chinese medicine (TCM) are reported causative for liver disease, with levels of causality proof that appear rarely conclusive. Encouraging steps in the field of herbal hepatotoxicity focus on introducing analytical methods that identify cases of intrinsic hepatotoxicity caused by pyrrolizidine alkaloids, and on omics technologies, including genomics, proteomics, metabolomics, and assessing circulating micro-RNA in the serum of some patients with intrinsic hepatotoxicity. It remains to be established whether these new technologies can identify idiosyncratic HILI cases. To enhance its globalization, herbal medicine should universally be marketed as herbal drugs under strict regulatory surveillance in analogy to regulatory approved chemical drugs, proving a positive risk/benefit profile by enforcing evidence based clinical trials and excellent herbal drug quality.

Fatal kavalactone intoxication by suicidal intravenous injection

Kavalactones are a group of compounds found in kava, a beverage or extract prepared from the rhizome of the kava plant (Piper methysticum). Traditionally kava extracts have been used for their anxiolytic and sedative properties. Sales of kava extracts were severely restricted or prohibited in European countries in 2002 following several cases of serious hepatotoxicity. Here we report a case where high concentrations of kavalactones and ethanol were detected in post mortem femoral blood. An injection needle with a 10-mL syringe containing 7.5 mL of slightly yellowish liquid was found next to the victim, and there were numerous needle prints on both lower arms following the venous tracks. No evidence of other cause of death was found in the medico-legal investigation. The case was therefore classified as suicide using an injection of kavalactones intravenously together with alcohol poisoning.

Contemporary Pacific and Western perspectives on `awa (Piper methysticum) toxicology

In 2010, a National Science Foundation project in Hawai`i assembled a collaboration of Pacific indigenous scientists, Hawaiian cultural practitioners and scientists trained in Western pharmacology. The objective of the collaborative project was to study Kava, a culturally significant Pacific beverage, and to address and ultimately transcend, long-standing barriers to communication and collaboration between these groups. Kava is a product of the `awa plant (Piper methysticum) that has been used ceremonially and medicinally throughout the history of Pacific Island cultures, and is now in widespread recreational and nutraceutical use in the US. This project, culminating in 2015, has enriched the participants, led to published work that integrates cultural and Western pharmacologic perspectives and established a paradigm for collaboration. This review paper integrates cultural and Western perspectives on efficacy, toxicity and the future cultural and commercial significance of `awa in the Pacific. Here we present a detailed review of traditional and non-traditional kava usage, medicinal efficacy and potential toxicological concerns. Recent mechanistic data on physiological action and potential pathological reactions are evaluated and interpreted.

Drug and herb induced liver injury: Council for International Organizations of Medical Sciences scale for causality assessment

Causality assessment of suspected drug induced liver injury (DILI) and herb induced liver injury (HILI) is hampered by the lack of a standardized approach to be used by attending physicians and at various subsequent evaluating levels. The aim of this review was to analyze the suitability of the liver specific Council for International Organizations of Medical Sciences (CIOMS) scale as a standard tool for causality assessment in DILI and HILI cases. PubMed database was searched for the following terms: drug induced liver injury; herb induced liver injury; DILI causality assessment; and HILI causality assessment. The strength of the CIOMS lies in its potential as a standardized scale for DILI and HILI causality assessment. Other advantages include its liver specificity and its validation for hepatotoxicity with excellent sensitivity, specificity and predictive validity, based on cases with a positive reexposure test. This scale allows prospective collection of all relevant data required for a valid causality assessment. It does not require expert knowledge in hepatotoxicity and its results may subsequently be refined. Weaknesses of the CIOMS scale include the limited exclusion of alternative causes and qualitatively graded risk factors. In conclusion, CIOMS appears to be suitable as a standard scale for attending physicians, regulatory agencies, expert panels and other scientists to provide a standardized, reproducible causality assessment in suspected DILI and HILI cases, applicable primarily at all assessing levels involved.

Herbal hepatotoxicity: suspected cases assessed for alternative causes

BACKGROUND AND OBJECTIVES

Alternative explanations are common in suspected drug-induced liver injury (DILI) and account for up to 47.1% of analyzed cases. This raised the question of whether a similar frequency may prevail in cases of assumed herb-induced liver injury (HILI).

METHODS

We searched the Medline database for the following terms: herbs, herbal drugs, herbal dietary supplements, hepatotoxic herbs, herbal hepatotoxicity, and herb-induced liver injury. Additional terms specifically addressed single herbs and herbal products: black cohosh, Greater Celandine, green tea, Herbalife products, Hydroxycut, kava, and Pelargonium sidoides. We retrieved 23 published case series and regulatory assessments related to hepatotoxicity by herbs and herbal dietary supplements with alternative causes.

RESULTS

The 23 publications comprised 573 cases of initially suspected HILI; alternative causes were evident in 278/573 cases (48.5%). Among them were hepatitis by various viruses (9.7%), autoimmune diseases (10.4%), nonalcoholic and alcoholic liver diseases (5.4%), liver injury by comedication (DILI and other HILI) (43.9%), and liver involvement in infectious diseases (4.7%). Biliary and pancreatic diseases were frequent alternative diagnoses (11.5%), raising therapeutic problems if specific treatment is withheld; pre-existing liver diseases including cirrhosis (9.7%) were additional confounding variables. Other diagnoses were rare, but possibly relevant for the individual patient.

CONCLUSION

In 573 cases of initially assumed HILI, 48.5% showed alternative causes unrelated to the initially incriminated herb, herbal drug, or herbal dietary supplement, calling for thorough clinical evaluations and appropriate causality assessments in future cases of suspected HILI.

Herbal hepatotoxicity: a tabular compilation of reported cases

BACKGROUND

Herbal hepatotoxicity is a field that has rapidly grown over the last few years along with increased use of herbal products worldwide.

AIMS

To summarize the various facets of this disease, we undertook a literature search for herbs, herbal drugs and herbal supplements with reported cases of herbal hepatotoxicity.

METHODS

A selective literature search was performed to identify published case reports, spontaneous case reports, case series and review articles regarding herbal hepatotoxicity.

RESULTS

A total of 185 publications were identified and the results compiled. They show 60 different herbs, herbal drugs and herbal supplements with reported potential hepatotoxicity, additional information including synonyms of individual herbs, botanical names and cross references are provided. If known, details are presented for specific ingredients and chemicals in herbal products, and for references with authors that can be matched to each herbal product and to its effect on the liver. Based on stringent causality assessment methods and/or positive re-exposure tests, causality was highly probable or probable for Ayurvedic herbs, Chaparral, Chinese herbal mixture, Germander, Greater Celandine, green tea, few Herbalife products, Jin Bu Huan, Kava, Ma Huang, Mistletoe, Senna, Syo Saiko To and Venencapsan(®). In many other publications, however, causality was not properly evaluated by a liver-specific and for hepatotoxicity-validated causality assessment method such as the scale of CIOMS (Council for International Organizations of Medical Sciences).

CONCLUSIONS

This compilation presents details of herbal hepatotoxicity, assisting thereby clinical assessment of involved physicians in the future.

Lung Tumorigenesis Suppressing Effects of a Commercial Kava Extract and Its Selected Compounds in A/J Mice

Lung cancer is the most deadly malignancy in the US. Chemoprevention is potentially a complementary approach to smoking cessation for lung cancer control. Recently, we reported that a commercially available form of kava extract significantly inhibits 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo(a)pyrene (BaP)-induced lung tumorigenesis in A/J mice at a dose of 10 mg per gram diet. In the present study, we examined the dose-dependent lung tumor inhibitory activities of kava and investigated potential active constituent(s). Mice treated with carcinogen alone contained 12.1±5.8 lung adenomas per mouse 22 weeks after final carcinogen administration. Mice that were fed diets containing kava at dosages of 1.25, 2.5, 5, and 10 mg/g of diet had 8.4±3.5, 6.6±3.5, 4.3±2.4, and 3.8±2.3 lung adenomas per mouse, respectively. This corresponds to a reduction of 31%, 46%, 65% and 69% in tumor multiplicity, which were all statistically significant (p < 0.05). Analyses of lung adenoma tissues derived from kava-treated animals revealed that kava significantly inhibited adenoma cell proliferation while it had no detectable effect on cell death, indicating that kava primarily suppressed lung tumorigenesis in A/J mice via inhibition of cell proliferation. Flavokawains A, B, and C, three chalcone-based components from kava, demonstrated greatly reduced chemopreventive efficacies even at concentrations much higher than their natural abundance, suggesting that they alone were unlikely to be responsible for kava's chemopreventive activity. Kava at all dosages and treatment regimens did not induce detectable adverse effects, particularly with respect to liver. Specifically, kava treatment showed no effect on liver integrity indicator enzymes or liver weight, indicating that kava may be potentially safe for long-term chemopreventive application.

Herbal remedies, mood, and cognition

Herbal medicines were the "sole" source of medicine for thousands of years, in every culture since the advent of human civilization. Today, patients are increasing the use of these botanicals for numerous conditions, such as mood and cognition. This article will explore commonly used herbal remedies for mood and cognition functioning. It is imperative that nurses and nurse practitioners obtain expertise with these botanicals with regard to efficacy, adverse effects and contraindications, possible drug interactions, and safety considerations.

Liver toxicity and carcinogenicity in F344/N rats and B6C3F1 mice exposed to Kava Kava

Kava Kava is an herbal supplement used as an alternative to antianxiety drugs. Although some reports suggest an association of Kava Kava with hepatotoxicity , it continues to be used in the United States due to lack of toxicity characterization. In these studies F344/N rats and B6C3F1 mice were administered Kava Kava extract orally by gavage in corn oil for two weeks, thirteen weeks or two years. Results from prechronic studies administered Kava Kava at 0.125 to 2g/kg body weight revealed dose-related increases in liver weights and incidences of hepatocellular hypertrophy. In the chronic studies, there were dose-related increases in the incidences of hepatocellular hypertrophy in rats and mice administered Kava Kava for up to 1g/kg body weight. This was accompanied by significant increases in incidences of centrilobular fatty change. There was no treatment- related increase in carcinogenic activity in the livers of male or female rats in the chronic studies. Male mice showed a significant dose-related increase in the incidence of hepatoblastomas. In female mice, there was a significant increase in the combined incidence of hepatocellular adenoma and carcinoma in the low and mid dose groups but not in the high dose group. These findings were accompanied by several nonneoplastic hepatic lesions.

Herbal hepatotoxicity by kava: update on pipermethystine, flavokavain B, and mould hepatotoxins as primarily assumed culprits

Herbal hepatotoxicity by the anxiolytic kava (Piper methysticum Forst. f.) emerged unexpectedly and was observed in a few patients worldwide. Liver injury occurred after the use of traditional aqueous kava extracts in the South Pacific region and of acetonic and ethanolic extracts in Western countries in rare cases, suggesting that the solvents used play no major causative role. In this review, we discuss actual pathogenetic issues of kava hepatotoxicity with special focus on developments regarding pipermethystine, flavokavain B, and mould hepatotoxins as possible culprits. There is abundant data of in vitro cytotoxicity including apoptosis by pipermethystine and flavokavain B added to the incubation media, yet evidence is lacking of in vivo hepatotoxicity in experimental animals under conditions similar to human kava use. Furthermore, in commercial Western kava extracts, pipermethystine was not detectable and flavokavain B was present as a natural compound in amounts much too low to cause experimental liver injury. There is concern, however, that due to high temperature and humidity in the South Pacific area, kava raw material might have been contaminated by mould hepatotoxins such as aflatoxins after harvest and during storage. Whether kava hepatotoxicity may be due to aflatoxicosis or other mould hepatotoxins, requires further studies.

Proposal for a kava quality standardization code

Rare cases of hepatotoxicity emerged with the use of kava drugs and dietary supplements prepared from rhizomes and roots of the South Pacific plant kava (Piper methysticum). Their psychoactive, anxiolytic, relaxing, and recreational ingredients are the kavalactones kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin, and desmethoxyyangonin, but there is little evidence that these kavalactones or the non-kavalactones pipermethystine and flavokavain B are the culprits of the adverse hepatic reactions. It rather appears that poor quality of the kava material was responsible for the liver toxicity. Analysis of existing kava quality standardizations with focus on chemical, agricultural, manufacturing, nutritional, regulatory, and legislation backgrounds showed major shortcomings that could easily explain quality problems. We therefore suggest a uniform, internationally accepted device for kava quality standardizations that are in the interest of the consumers because of safety reasons and will meet the expectations of kava farmers, pharmaceutical manufacturers, regulators of agencies, and legislators. The initial step resides in the establishment of Pan-Pacific kava quality legislation as an important part of the proposed Kava Quality Standardization Code. In conclusion, a sophisticated approach to establish kava quality standardizations is needed for safe human use of kava as relaxing traditional beverages, the anxiolytic drugs, and recreational dietary supplements.

Tradition and toxicity: evidential cultures in the kava safety debate

This paper examines the debate about the safety of kava (Piper methysticum Forst. f, Piperaceae), a plant native to Oceania, where it has a long history of traditional use. Kava became popular as an anti-anxiety treatment in Western countries in the late 1990s, but it was subsequently banned in many places due to adverse reports of liver toxicity. This paper focuses on the responses to the bans by scientists involved in kava research, contrasting their evidential culture with that employed by clinicians and regulatory officials. Cultural constructions and social negotiations of risk are shown to be context-specific, and are shaped by professional, disciplinary, and organizational factors, among others. Though the science of hepatotoxicity is uncertain enough to allow for multiple interpretations of the same data, the biomedical/clinical narrative about kava remains dominant. This case study explores the influence of these cultural, social, and political factors on the production of scientific knowledge and the assessment of benefit/risk posed by comestibles.

Kava, the anxiolytic herb: back to basics to prevent liver injury?

The use of the anxiolytic herb kava has caused toxic liver injury in Western countries and economic problems in South Pacific Islands due to tthe regulatory ban on kava. This analysis shows poor quality of kava raw material as a cause for its toxicity and suggests preventative measures by going back to the traditional use of kava for the sake of the patients and the South Pacific economy.

Constituents in kava extracts potentially involved in hepatotoxicity: a review

Aqueous kava root preparations have been consumed in the South Pacific as an apparently safe ceremonial and cultural drink for centuries. However, several reports of hepatotoxicity have been linked to the consumption of kava extracts in Western countries, where mainly ethanolic or acetonic extracts are used. The mechanism of toxicity has not been established, although several theories have been put forward. The composition of the major constituents, the kava lactones, varies according to preparation method and species of kava plant, and thus, the toxicity of the individual lactones has been tested in order to establish whether a single lactone or a certain composition of lactones may be responsible for the increased prevalence of kava-induced hepatotoxicity in Western countries. However, no such conclusion has been made on the basis of current data. Inhibition or induction of the major metabolizing enzymes, which might result in drug interactions, has also gained attention, but ambiguous results have been reported. On the basis of the chemical structures of kava constituents, the formation of reactive metabolites has also been suggested as an explanation of toxicity. Furthermore, skin rash is a side effect in kava consumers, which may be indicative of the formation of reactive metabolites and covalent binding to skin proteins leading to immune-mediated responses. Reactive metabolites of kava lactones have been identified in vitro as glutathione (GSH) conjugates and in vivo as mercapturates excreted in urine. Addition of GSH to kava extracts has been shown to reduce cytotoxicity in vitro, which suggests the presence of inherently reactive constituents. Only a few studies have investigated the toxicity of the minor constituents present in kava extract, such as pipermethystine and the flavokavains, where some have been shown to display higher in vitro cytotoxicity than the lactones. To date, there remains no indisputable reason for the increased prevalence of kava-induced hepatotoxicity in Western countries.

Kava and kava hepatotoxicity: requirements for novel experimental, ethnobotanical and clinical studies based on a review of the evidence

Kava hepatotoxicity is a well described disease entity, yet there is uncertainty as to the culprit(s). In particular, there is so far no clear evidence for a causative role of kavalactones and non-kavalactone constituents, such as pipermethystine and flavokavain B, identified from kava. Therefore, novel enzymatic, analytical, toxicological, ethnobotanical and clinical studies are now required. Studies should focus on the identification of further potential hepatotoxic constituents, considering in particular possible adulterants and impurities with special reference to ochratoxin A and aflatoxins (AFs) producing Aspergillus varieties, which should be urgently assessed and published. At present, Aspergillus and other fungus species producing hepatotoxic mycotoxins have not yet been examined thoroughly as possible contaminants of some kava raw materials. Its occurence may be facilitated by high humidity, poor methods for drying procedures and insufficient storage facilities during the time after harvest. Various experimental studies are recommended using aqueous, acetonic and ethanolic kava extracts derived from different plant parts, such as peeled rhizomes and peeled roots including their peelings, and considering both noble and non-noble kava cultivars. In addition, ethnobotanical studies associated with local expertise and surveillance are required to achieve a good quality of kava as the raw material. In clinical trials of patients with anxiety disorders seeking herbal anxiolytic treatment with kava extracts, long-term safety and efficacy should be tested using traditional aqueous extracts obtained from peeled rhizomes and peeled roots of a noble kava cultivar, such as Borogu, to evaluate the risk: benefit ratio. Concomitantly, more research should be conducted on the bioavailability of kavalactones and non-kavalactones derived from aqueous kava extracts. To be on the side of caution and to ensure lack of liver injury, kava consuming inhabitants of the kava producing or importing South Pacific islands should undergo assessment of their liver function values and serum aflatoxin levels. The primary aim is to achieve a good quality of kava raw material, without the risk of adulterants and impurities including ochratoxin A and AFs, which represent the sum of aflatoxin B1, B2, G1 and G2. Although it is known that kava may naturally be contaminated with AFs, there is at present no evidence that kava hepatotoxicity might be due to aflatoxicosis. However, appropriate studies have yet to be done and should be extended to other mould hepatotoxins, with the aim of publishing the obtained results. It is hoped that with the proposed qualifying measures, the safety of individuals consuming kava will substantially be improved.

Neurocognitive effects of kava (Piper methysticum): a systematic review

RATIONALE

Kava (Piper methysticum) elicits dose-dependent psychotropic effects and thus may potentially deleteriously affect cognitive performance. Clinical trials have assessed the effects of kava on cognition, however, to our knowledge no systematic review has been conducted in this area.

OBJECTIVE

To systematically review the effects of kava on cognition, providing an analysis of the individual study's methodological quality, results and effect sizes.

METHODS

A systematic review was conducted of publications up to June 15th 2010, using the electronic databases MEDLINE, PsychINFO, CINAHL, Web of Science and The Cochrane Library. The search criteria involved kava and cognition related terms, e.g. memory and attention.

RESULTS

Ten human clinical trials met inclusion criteria (acute n = 7, chronic n = 3). One acute study found that kava significantly improved visual attention and working memory processes while another found that kava increased body sway. One chronic study found that kava significantly impaired visual attention during high-cognitive demand. Potential enhanced cognition may be attributed to the ability of kava to inhibit re-uptake of noradrenaline in the pre-frontal cortex, while increased body sway may be due to GABA pathway modulation.

CONCLUSIONS

The majority of evidence suggests that kava has no replicated significant negative effects on cognition.

Kava hepatotoxicity: comparative study of two structured quantitative methods for causality assessment

BACKGROUND AND OBJECTIVE

Ingestion of the medicinal herb kava has been associated with hepatotoxicity. We aimed to compare two different quantitative methods of causality assessment of patients with assumed hepatotoxicity by the herb.

METHODS

We assessed causality in 26 patients from Germany and Switzerland, using two structured quantitative analytical methods: the system of Maria and Victorino (MV) and that of the Council for International Organizations of Medical Sciences (CIOMS). In all 26 patients, regulatory ad hoc evaluation had suggested a causal relationship between liver disease and kava use.

RESULTS AND DISCUSSION

Assessment with the MV scale resulted in no or low graded causality for kava in the 26 patients with liver disease. Causality was probable (n=1), possible (n=2), unlikely (n=7), and excluded (n=16). Causality for kava was more evident with the CIOMS scale: highly probable (n=1), probable (n=2), possible (n=6), unlikely (n=2) and excluded (n=15). However, the results of both quantitative causality assessments are not supportive for most of the regulatory ad hoc causality assessments of the 26 patients.

CONCLUSION

Grades of causality for suspected hepatotoxicity by kava were much lower when evaluated by structured quantitative causality assessment scales than by regulatory ad hoc judgements. The quantitative CIOMS scale is the preferable tool for causality assessment of spontaneous reports of hepatotoxcity involving kava.

Kava hepatotoxicity solution: A six-point plan for new kava standardization

Kava-induced liver injury has been demonstrated in a few patients worldwide and appears to be caused by inappropriate quality of the kava raw material. When cases of liver disease in connection with the use of kava emerged, this was an unexpected and challenging event considering the long tradition of safe kava use. In order to prevent kava hepatotoxicity in future, a set of quality specifications as standard is essential for the preparation not only of kava drugs and kava dietary supplements in the Western world but also for traditional kava drinks in the South Pacific Islands. For all these purposes a uniform approach is required, using water based extracts from the peeled rhizomes and roots of a noble cultivar such as Borogu with at least 5 years of age at the time of harvest. Cultivated in Vanuatu for centuries, noble varieties (as defined in the Vanuatu Kava Act of December 2002) are well tolerated traditional cultivars with a good safety record. At present, Vanuatu kava legislation is inadequately enforced to meet quality issues for kava, and further efforts are required in Vanuatu, in addition to similar legislation in other kava producing South Pacific Islands. Future regulatory and commercial strategies should focus not only on the standardization of kava drugs, kava dietary supplements, and traditional kava extracts, but also on thorough surveillance during the manufacturing process to improve kava quality for safe human use. The efficacy of kava extracts to treat patients with anxiety disorders is well supported, but further clinical trials with aqueous kava extracts are necessary. We thereby propose a six-point kava solution plan: (1) use of a noble kava cultivar such as Borogu, at least 5 years old at time of harvest, (2) use of peeled and dried rhizomes and roots, (3) aqueous extraction, (4) dosage recommendation of ≤250mg kavalactones per day (for medicinal use), (5) systematic rigorous future research, and (6) a Pan Pacific quality control system enforced by strict policing. In conclusion, at different levels of responsibility, new mandatory approaches are now required to implement quality specification for international acceptance of kava as a safe and effective anxiolytic herb.

Regulatory causality evaluation methods applied in kava hepatotoxicity: are they appropriate?

Since 1998 liver injury has been assumed in some patients after the use of kava (Piper methysticum G. Forster) as an anxyolytic herbal extract, but the regulatory causality evaluation of these cases was a matter of international and scientific debate. This review critically analyzes the regulatory issues of causality assessments of patients with primarily suspected kava hepatotoxicity and suggests recommendations for minimizing regulatory risks when assessing causality in these and other related cases. The various regulatory causality approaches were based on liver unspecific assessments such as ad hoc evaluations, the WHO scale using the definitions of the WHO Collaborating Centre for International Drug Monitoring, and the Naranjo scale. Due to their liver unspecificity, however, these causality approaches are not suitable for assessing cases of primarily assumed liver related adverse reactions by drugs and herbs including kava. Major problems emerged trough the combination of regulatory inappropriate causality assessment methods with the poor data quality as presented by the regulatory agency when reassessment was done and the resulting data were heavily criticized worldwide within the scientific community. Conversely, causality of cases with primarily assumed kava hepatotoxicity is best assessed by structured, quantitative and liver specific causality algorithms such as the scale of the CIOMS (Council for International Organizations of Medical Sciences) or the main-test as its update. Future strategies should therefore focus on the implementation of structured, quantitative and liver specific causality assessment methods as regulatory standards to improve regulatory causality assessments for liver injury by drugs and herbs including kava.

Kava hepatotoxicity: regulatory data selection and causality assessment

BACKGROUND

Kava hepatotoxicity in 20 patients from Germany has been debated worldwide following a regulatory ad hoc causality assessment and ban of kava, an anxiolytic herbal remedy obtained from the rhizome of Piper methysticum Forster.

AIMS

We assessed causality with a quantitative structured causality analysis in all 20 cases of patients with liver disease, presented by the German regulatory agency that assumed a causal relationship with the use of kava extracts.

METHODS

The quantitative scale of CIOMS (Council for International Organizations of Medical Sciences) in its updated form was employed for causality assessment and quality evaluation of the regulatory data presentation.

RESULTS

The regulatory information is scattered and selective, and items essential for causality assessment, such as exclusion of kava independent causes, were not, or only marginally, considered by the regulator. Quantitative causality assessment for kava was possible (n=2), unlikely (n=12), or excluded (n=6), showing no concordance with the regulatory ad hoc causality evaluation.

CONCLUSION

The regulatory data regarding kava hepatotoxicity is selective and of low quality, not supportive of the regulatory proposed causality; but instead, is an explanation of the overall causality discussions of kava hepatotoxicity. We are proposing that the regulatory agency reports data in full length and reevaluates causality.

Kava hepatotoxicity: comparison of aqueous, ethanolic, acetonic kava extracts and kava-herbs mixtures

ETHNOPHARMACOLOGICAL RELEVANCE

Ethanolic and acetonic kava extracts have previously been causally related to rare hepatotoxicity observed in patients from Germany and Switzerland, but causality assessment was not performed in cases of patients having taken the traditional aqueous kava extracts of South Pacific islands or kava-herbs mixtures.

AIM OF THE STUDY

To study the possible hepatotoxicity of aqueous kava extracts of the South Pacific Islands.

MATERIALS AND METHODS

Causality of hepatotoxicity by aqueous kava extracts and kava-herbs mixtures was assessed, using the updated score of the quantitative CIOMS (Council for the International Organizations of Medical Sciences).

RESULTS

Causality was established in five patients from New Caledonia, Australia, the United States and Germany for aqueous kava extracts and kava-herbs mixtures. A comparison with 9 patients from Germany and Switzerland with established causality of hepatotoxicity by ethanolic and acetonic kava extracts reveals that the clinical picture in all 14 patients is similar, independently whether aqueous, ethanolic and acetonic kava extracts or kava-herbs mixtures were used.

CONCLUSIONS

Kava hepatotoxicity occurs also with traditional aqueous kava extracts of the South Pacific islands and thereby independently from ethanol or acetone as chemical solvents, suggesting that the toxicity is linked to the kava plant itself with a possibly low quality of the used kava cultivar or kava plant part rather than to chemical solvents.

Kava hepatotoxicity: a clinical survey and critical analysis of 26 suspected cases

BACKGROUND/AIMS

Hepatotoxicity has been previously suspected by national regulatory agencies in 26 patients in causal relationship with the treatment by kava extracts commonly used as herbal anxiolytic drugs.

METHODS

A quantitative causality assessment was undertaken using the system of the Council for International Organizations of Medical Sciences, scale of objective probability scoring.

RESULTS

Causality was unassessable, unrelated, or excluded in 16 patients owing to lack of temporal association and causes independent of kava or comedicated drugs. Low Council for International Organizations of Medical Sciences scores additionally resulted in excluded or unlikely causality assessments (n=2), leaving a total of eight patients with various degrees of causality for kava +/- comedicated drugs. Only one out of these eight patients adhered to the regulatory recommendations regarding both daily dose (<or=120 mg kavapyrones) and duration of therapy (<or=3 months) and experienced toxic liver injury with a probable causality for kava. In six cases with kava overdose and/or increased duration of kava treatment causality for kava was possible (n=3) and for kava together with the comedicated drug(s) possible (n=2) or probable (n=1).

CONCLUSION

Kava taken as recommended is associated with rare hepatotoxicity, whereas overdose, prolonged treatment, and comedication may carry an increased risk.

Hepatotoxicity associated with herbal products

A significant number of herbal products have been associated with hepatotoxicity. Attribution of liver injury to a specific herbal pro-duct may be difficult. There are few clinical or laboratory manifestations that specifically suggest that liver injury is the result of aspecific herbal. Compounding this difficulty is that the patient may have liver disease from another cause, may be consuming other potentially hepatotoxic products, or may be using a contaminated herbal product. The most important clue often is the temporal relationship between initiation of the herbal product and the appearance of liver injury; of equal importance is the resolution of the injury following withdrawal of the herbal product.

In vitro cytotoxicity of nonpolar constituents from different parts of kava plant (Piper methysticum)

Kava (Piper methysticum), a perennial shrub native to the South Pacific islands, has been used to relieve anxiety. Recently, several cases of severe hepatotoxicity have been reported from the consumption of dietary supplements containing kava. It is unclear whether the kava constituents, kavalactones, are responsible for the associated hepatotoxicity. To investigate the key components responsible for the liver toxicity, bioassay-guided fractionation was carried out in this study. Kava roots, leaves, and stem peelings were extracted with methanol, and the resulting residues were subjected to partition with a different polarity of solvents (hexane, ethyl acetate, n-butanol, and water) for evaluation of their cytotoxicity on HepG2 cells based on the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and lactate dehydrogenase and aspartate aminotransferase enzyme leakage assays. Organic solvent fractions displayed a much stronger cytotoxicity than water fractions for all parts of kava. The hexane fraction of the root exhibited stronger cytotoxic effects than fractions of root extracted with other solvents or extracts from the other parts of kava. Further investigations using bioassay-directed isolation and analysis of the hexane fraction indicated that the compound responsible for the cytotoxicity was flavokavain B. The identity of the compound was confirmed by (1)H and (13) C NMR and MS techniques.

Meta-analysis of the efficacy of the acetonic kava-kava extract WS1490 in patients with non-psychotic anxiety disorders

INTRODUCTION

The herbal medicinal product kava-kava, used for treating anxiety disorders, was assessed positively by the Cochrane Review. However, it was withdrawn from the market in Switzerland and Germany due to cases of liver failure and 'unproven' efficacy.

METHODS

A protocol for the meta-analysis based on patient source data was written, a literature search was done, and six placebo-controlled, randomized trials with the kava extract WS1490 were identified. The endpoints were the change in HAMA during treatment (continuous and binary).

RESULTS

WS1490 has an effective success rate of OR=3.3 (95% confidence interval of 2.09-5.22) in patients with non-psychotic anxiety disorders. The continuous outcome supports this result: mean improvement with WS1490 by 5.94 (95% confidence interval -0.86 to 12.8) points on the HAMA scale better than placebo. Kava seems to be more effective in females and in younger patients.

DISCUSSION

This meta-analysis has no publication bias, no remarkable heterogeneity and is based on trials with high methodological standards. It is concluded that WS1490, and possibly other kava extracts, are effective. Therefore they remain alternatives to benzodiazepines, selective serotonin re-uptake inhibitors (SSRIs) and other antidepressants in the treatment of non-psychotic anxiety disorders.

Safety review of kava (Piper methysticum) by the Natural Standard Research Collaboration

This systematic review discusses the proposed uses, dosing parameters, adverse effects, toxicology, interactions and mechanism of action of kava. The widespread concern regarding the potential hepatotoxicity of kava is discussed. A recommendation is made to consolidate and analyse available reports and to continue postmarket surveillance in an international repository to prevent duplicates and promote collection of thorough details at the time of each report so that any association with kava is clearly defined.

Food-drug interactions via human cytochrome P450 3A (CYP3A)

Food-drug interactions have been reported to occur in various systems in the body. The causes of these interactions are mainly divided into pharmacodynamic and pharmacokinetic processes. Among these processes, drug metabolism plays a crucial role in drug interactions. Metabolic food-drug interactions occur when a certain food alters the activity of a drug-metabolizing enzyme, leading to a modulation of the pharmacokinetics of drugs metabolized by the enzyme. A variety of interactions have been documented so far. Foods consisting of complex chemical mixtures, such as fruits, alcoholic beverages, teas, and herbs, possess the ability to inhibit or induce the activity of drug-metabolizing enzymes. According to results obtained thus far, cytochrome P450 3A4 (CYP3A4) appears to be a key enzyme in food-drug interactions. For example, interactions of grapefruit juice with felodipine and cyclosporine, red wine with cyclosporine, and St John's wort with various medicines including cyclosporine, have been demonstrated. The results indicate the requirement of dosage adjustment to maintain drug concentrations within their therapeutic windows. The CYP3A4-related interaction by food components may be related to the high level of expression of CYP3A4 in the small intestine, as well as its broad substrate specificity, as CYP3A4 is responsible for the metabolism of more than 50% of clinical pharmaceuticals. This review article summarizes the findings obtained to date concerning food-drug interactions and their clinical implications. It seems likely that more information regarding such interactions will accumulate in the future, and awareness is necessary for achieving optimal drug therapy.

Microbial metabolism. Part 5. Dihydrokawain

Preparative scale fermentation of (6S)-dihydrokawain (1) with Rhizopus arrhizus (ATCC 11145) gave 3'-hydroxydihydrokawain (2) and (8S)-hydroxydihydrokawain (3). Structure elucidation of the metabolites was based on spectroscopic data. The C-8 absolute configuration of (3) was assessed via its Mosher's esters.

Composition and biological activity of traditional and commercial kava extracts

For centuries the South Pacific islanders have consumed kava (Piper methysticum) as a ceremonial intoxicating beverage. More recently, caplets of kava extracts have been commercialized for their anxiolytic and antidepressant activities. Several cases of hepatotoxicity have been reported following consumption of the commercial preparation whereas no serious health effects had been documented for the traditional beverage. A detailed comparison of commercial kava extracts (prepared in acetone, ethanol or methanol) and traditional kava (aqueous) reveals significant differences in the ratio of the major kavalactones. To show that these variations could lead to differences in biological activity, the extracts were compared for their inhibition of the major drug metabolizing P450 enzymes. In all cases (CYP3A4, CYP1A2, CYP2C9, and CYP2C19), the inhibition was more pronounced for the commercial preparation. Our results suggest that the variations in health effects reported for the kava extracts may result from the different preparation protocols used.

Herbal remedies in the United States: potential adverse interactions with anticancer agents

PURPOSE

Interest in the use of herbal products has grown dramatically in the Western world. Recent estimates suggest an overall prevalence for herbal preparation use of 13% to 63% among cancer patients. With the narrow therapeutic range associated with most anticancer drugs, there is an increasing need for understanding possible adverse drug interactions in medical oncology.

METHODS

In this article, a literature overview is provided of known or suspected interactions of the 15 best-selling herbs in the United States with conventional allopathic therapies for cancer.

RESULTS

Herbs with the potential to significantly modulate the activity of drug-metabolizing enzymes (notably cytochrome p450 isozymes) and/or the drug transporter P-glycoprotein include garlic (Allium sativum), ginkgo (Ginkgo biloba), echinacea (Echinacea purpurea), ginseng (Panax ginseng), St John' s wort (Hypericum perforatum), and kava (Piper methysticum). All of these products participate in potential pharmacokinetic interactions with anticancer drugs.

CONCLUSION

It is suggested that health care professionals and consumers should be aware of the potential for adverse interactions with these herbs, question their patients on their use of them, especially among patients whose disease is not responding to treatments as expected, and urge patients to avoid herbs that could confound their cancer care.

Kava kava: examining new reports of toxicity

Before 1998, extracts of kava kava, Piper methysticum, were considered to be very safe alternatives to anxiolytic drugs and to possibly exert a wide range of other benefits. Major reviews published through the end of 2002 continued to confirm kava's safety and efficacy. Nevertheless, by January 2003 kava extracts had been banned in the entire European Union and Canada, and were subject to cautions and advisories by the US FDA as a result of 11 cases of hepatic failure leading to liver transplants, including four deaths. A total of 78 cases of hepatotoxicity reputedly linked to kava ingestion are available for review from various databases. Of these adverse events, four probably are linked to kavalactones taken alone and another 23 are potentially linked to kava intake, but also involve the concomitant ingestion of other compounds with potential hepatotoxicity. Three possible mechanisms for kavalactone hepatotoxicity are known: inhibition of cytochrome P450, reduction in liver glutathione content and, more remotely, inhibition of cyclooxygenase enzyme activity. The direct toxicity of kava extracts is quite small under any analysis, yet the potential for drug interactions and/or the potentiation of the toxicity of other compounds is large. Presently, kava toxicity appears to be "idiosyncratic." The risk-to-benefit ratio of kava extracts, nevertheless, remains good in comparison with that of other drugs used to treat anxiety.

Kava lactones and the kava-kava controversy

Kava-kava is a traditional beverage of the South Pacific islanders and has had centuries of use without major side effects. Standardised extracts of kava-kava produced in Europe have led to many serious health problems and even to death. The extraction process (aqueous vs. acetone in the two types of preparations) is responsible for the difference in toxicity as extraction of glutathione in addition to the kava lactones is important to provide protection against hepatotoxicity. The Michael reaction between glutathione and kava lactones, resulting in opening of the lactone ring, reduces the side effects of the kava kava extracts. This protective activity was demonstrated using Acanthamoebae castellanii in which 100% cell death occurred with 100 mg ml(-1) kava lactones alone, and 40% cell death with a mixture of 100 mg ml (-1)glutathione and 100 mg ml (-1) kava lactones. A comparison of kava lactone toxicity with other pharmaceutical products is discussed and recommendations made for safe usage of kava-kava products

Plants and the central nervous system

This review article draws the attention to the many species of plants possessing activity on the central nervous system (CNS). In fact, they cover the whole spectrum of central activity such as psychoanaleptic, psycholeptic and psychodysleptic effects, and several of these plants are currently used in therapeutics to treat human ailments. Among the psychoanaleptic (stimulant) plants, those utilized by human beings to reduce body weight [Ephedra spp. (Ma Huang), Paullinia spp. (guaraná), Catha edulis Forssk. (khat)] and plants used to improve general health conditions (plant adaptogens) were scrutinized. Many species of hallucinogenic (psychodysleptic) plants are used by humans throughout the world to achieve states of mind distortions; among those, a few have been used for therapeutic purposes, such as Cannabis sativa L., Tabernanthe iboga Baill. and the mixture of Psychotria viridis Ruiz and Pav. and Banisteriopsis caapi (Spruce ex Griseb.) C.V. Morton. Plants showing central psycholeptic activities, such as analgesic or anxiolytic actions (Passiflora incarnata L., Valeriana spp. and Piper methysticum G. Forst.), were also analysed.Finally, the use of crude or semipurified extracts of such plants instead of the active substances seemingly responsible for their therapeutic effect is discussed.

Kava: herbal panacea or liver poison?

Following reports of liver toxicity, including liver failure, associated with extracts from the Pacific islands plant kava (Piper methysticum), these have been banned from sale as a herbal anxiolytic in many Western countries, to the detriment of Pacific island economies. Pacific Islanders have used kava extensively for centuries, without recognised liver toxicity. However, the population is small, and there has been no systematic evaluation of possible liver damage. For both economic and public health reasons, it is important to determine if kava is inherently hepatotoxic, and what the mechanisms of toxicity are. Such research could lead to safer kava extracts for sale in Western countries, or identification of a subpopulation who should not consume kava.