Milk Thistle

herb silymarin
(milk thistle)

Many HCV patients use the herb silymarin (milk thistle), an alternative therapy for HCV, in addition to or instead of standard treatment for chronic hepatitis C virus infection. In a survey of patients with chronic hepatitis C who participated in a National Institute of Diabetes and Digestive and Kidney Diseases-sponsored long-term treatment trial for patients who had failed to respond previously to antiviral therapy, approximately 40% acknowledged to interviewers at the time of enrollment that they were currently using or had in the recent past used herbal products for health purposes.

This information was somewhat surprising because these were patients with advanced liver disease who were clearly committed to conventional antiviral treatment for chronic hepatitis C, having been so treated previously, some on more than one occasion, but because they had failed to respond, were now willing to accept treatment again with pegylated interferon for another 3 and a half years.

Among those who were or had used alternative therapies, silymarin was the product of choice either on its own or together with other herbal products, representing 72% of all the herbals taken.

These study results appear in the February 2008 issue of Hepatology, published by Wiley & Sons on behalf of the American Association for the Study of Liver Diseases (AASLD). The article was is also available online at Wiley Interscience.

These results do not come from a rigorous scientific study because the products used were self-administered by the patients who entered the trial and no information was obtained on the duration or dose of the herbal taken. Still, in comparing users with non-users, while no difference was found for blood ALT or HCV levels between the two groups, the herbal users did report somewhat fewer symptoms and a better quality of life.

The current recommended treatment for patients with HCV infection is combination therapy with pegylated interferon and ribavirin. However, it leads to a sustained virological response (SVR) in only a third to a half of all patients with the predominant form of the infection in the U.S., namely genotype 1, and it can cause unpleasant and sometimes serious side effects.

HALT-C Trial

The NIH study, referred to as the Hepatitis C Antiviral Long-Term Treatment against Cirrhosis (HALT-C) Trial, was designed, therefore, to treat persons with advanced chronic hepatitis C who had failed previous antiviral therapy with the hope that the long-term treatment would reduce progression of the chronic liver disease even if it did not affect the virus itself.

The reason for interviewing enrollees in the trial was to determine the extent of use of alternative therapies in this committed group, since the popularity of herbal products has increased in the U.S., many HCV patients choosing to supplement, or even replace, the standard treatment with herbals. Silymarin (milk thistle extract) has been the most popular option for people with liver disease. Although it is the most frequent product utilized, silymarin has not been rigorously studied using accepted scientific approaches, and therefore such studies are clearly required and warranted.

For the present survey, researchers interviewed all HALT-C participants on past and current use of all prescription and non-prescription drugs, including herbal medications, dietary supplements and other botanical products. Of 1145 study participants, 56 percent said that they had never used herbal products, while 23 percent were using them currently, some 60 different articles. Silymarin was by far the most common. Usage was higher among men, among non-Hispanic whites, and among the more highly educated. Interestingly, the researchers also found geographic disparities in silymarin usage. It was most popular in Colorado, Michigan and Southern California and least popular in Maryland and Massachusetts.

Conclusions

In comparing the clinical data of silymarin users and non-users, the researchers found that "the levels of HCV RNA were not significantly different between silymarin users and non-users," indicating no effect on virus activity. Similarly, the product did not alter serum ALT levels, indicating no effect on hepatic inflammation. However, after adjusting for covariates, the data showed that silymarin users reported less fatigue, nausea, liver pain, anorexia, muscle and joint pain and better general health than non-users.

The better scores in a small number of symptoms among silymarin users compared to non-users are insufficient to support the value of this alternative therapy, the authors conclude. Compelling information can come only if a scientifically valid study is performed. "Currently in progress, therefore, is a properly designed prospective, randomized, controlled trial in which a fully characterized, purified and standardized silymarin formulation is being evaluated," they report.

This trial is supported by the National Center for Complementary and Alternative Medicine (NCCAM) and by NIDDK, NIH.

2/05/08

Reference
L Seeff, T Curto, G Szabo, and others. Herbal Product Use by Persons Enrolled in the Hepatitis C Antiviral Long-Term Treatment against Cirrhosis (Halt-C) Trial. Hepatology 47(2): 605-612. February 2008.

Milk Thistle: Effects on Liver Disease and Cirrhosis and Clinical Adverse Effects

Under its Evidence-based Practice Program, the Agency for Healthcare Research and Quality (AHRQ) is developing scientific information for other agencies and organizations on which to base clinical guidelines, performance measures, and other quality improvement tools. Contractor institutions review all relevant scientific literature on assigned clinical care topics and produce evidence reports and technology assessments, conduct research on methodologies and the effectiveness of their implementation, and participate in technical assistance activities. This evidence report details a systematic review summarizing clinical studies of milk thistle in humans.

Overview

The scientific name for milk thistle is Silybum marianum. It is a member of the aster or daisy family and has been used by ancient physicians and herbalists to treat a range of liver and gallbladder diseases and to protect the liver against a variety of poisons.

· Effects of milk thistle on liver disease of alcohol, viral, toxin, cholestatic, and primary malignancy etiologies.

The report was requested by the National Center for Complementary and Alternative Medicine, a component of the National Institutes of Health, and sponsored by the Agency for Healthcare Research and Quality.

Reporting the Evidence

Specifically, the report addresses 10 questions regarding whether milk thistle supplements (when compared with no supplement, placebo, other oral supplements, or drugs):

One question addresses the constituents of commonly available milk thistle preparations, and three questions address the common and uncommon symptomatic adverse effects of milk thistle.

Methodology

Search Strategy

Eleven electronic databases, including AMED, CISCOM, the Cochrane Library (including DARE and the Cochrane Controlled Trials Registry), EMBASE, MEDLINE, and NAPRALERT, were searched through July 1999 using the following terms:

An update search limited to PubMed was conducted in December 1999. English and non-English citations were identified from these electronic databases, references in pertinent articles and reviews, drug manufacturers, and technical experts.

Selection Criteria

Preliminary selection criteria regarding efficacy were reports on liver disease and clinical and physiologic outcomes from randomized controlled trials (RCTs) in humans comparing milk thistle with placebo, no milk thistle, or another active agent. Several of these randomized trials had dissimilar numbers of subjects in study arms, raising the question that these were not actually RCTs but cohort studies. In addition, among studies using non placebo controls, the type of control varied widely. Therefore, qualitative and quantitative syntheses of data on effectiveness were limited to placebo-controlled studies. For adverse effects, all types of studies in humans were used to assess adverse clinical effects.

Data Collection and Analysis

Abstractors (physicians, methodologists, pharmacists, and a nurse) independently abstracted data from trials; a nurse and physician abstracted data about adverse effects. Data were synthesized descriptively, emphasizing methodologic characteristics of the studies, such as populations enrolled, definitions of selection and outcome criteria, sample sizes, adequacy of randomization process, interventions and comparisons, cointerventions, biases in outcome assessment, and study designs.

Evidence tables and graphic summaries, such as funnel plots, Galbraith plots, and forest plots, were used to examine relationships between clinical outcomes, participant characteristics, and methodologic characteristics. Trial outcomes were examined quantitatively in exploratory meta-analyses that used standardized mean differences between mean change scores as the effect size measure.

Findings

Mechanisms of Action

Evidence exists that milk thistle may be hepatoprotective through a number of mechanisms: antioxidant activity, toxin blockade at the membrane level, enhanced protein synthesis, antifibriotic activity, and possible anti-inflammatory or immunomodulating effects.

Preparations of Milk Thistle

The largest producer of milk thistle is Madaus (Germany), which makes an extract of concentrated silymarin. However, numerous other extracts exist, and more information is needed on comparability of formulations, standardization, and bioavailability for studies of mechanisms of action and clinical trials.

Benefit of Milk Thistle for Liver Disease

· Sixteen prospective trials were identified. Fourteen were randomized, blinded, placebo-controlled studies of milk thistle's effectiveness in a variety of liver diseases. In one additional placebo-controlled trial, blinding or randomization was not clear, and one placebo-controlled study was a cohort study with a placebo comparison group.

· Seventeen additional trials used non placebo controls; two other trials studied milk thistle as prophylaxis in patients with no known liver disease who were starting potentially hepatotoxic drugs. The identified studies addressed alcohol-related liver disease, toxin-induced liver disease, and viral liver disease. No studies were found that evaluated milk thistle for cholestatic liver disease or primary hepatic malignancy (hepatocellular carcinoma, cholangiocarcinoma).

· There were problems in assessing the evidence because of incomplete information about multiple methodologic issues, including etiology and severity of liver disease, study design, subject characteristics, and potential confounders. It is difficult to say if the lack of information reflects poor scientific quality of study methods or poor reporting quality or both.

· Detailed data evaluation and syntheses were limited to the 16 placebo-controlled studies. Distribution of durations of therapy across trials was wide (7 days to 2 years), inconsistent, and sometimes not given. Eleven studies used Legalon®, and eight of those used the same dose. Outcome measures varied among studies, as did duration of therapy and the followup for which outcome measures were reported.

· Among six studies of milk thistle and chronic alcoholic liver disease, four reported significant improvement in at least one measurement of liver function (i.e., aminotransferases, albumin, and/or malondialdehyde) or histologic findings with milk thistle compared with placebo, but also reported no difference between groups for other outcome measures.

· Available data were insufficient to sort six studies into specific etiologic categories; these were grouped as chronic liver disease of mixed etiologies. In three of the six studies that reported multiple outcome measures, at least one outcome measure improved significantly with milk thistle compared with placebo, but there were no differences between milk thistle and placebo for one or more of the other outcome measures in each study. Two studies indicated a possible survival benefit.

· Three placebo-controlled studies evaluated milk thistle for viral hepatitis. The one acute viral hepatitis study reported latest outcome measures at 28 days and showed significant improvement in aspartate aminotransferase and bilirubin. The two studies of chronic viral hepatitis differed markedly in duration of therapy (7 days and 1 year). The shorter study showed improvement in aminotransferases for milk thistle compared with placebo but not other laboratory measures. In the longer study, milk thistle was associated with a nonsignificant trend toward histologic improvement, the only outcome measure reported.

· Two trials included patients with alcoholic or nonalcoholic cirrhosis. The milk thistle arms showed a trend toward improved survival in one trial and significantly improved survival for subgroups with alcoholic cirrhosis or Child's Group A severity. The second study reported no significant improvement in laboratory measures and survival for other clinical subgroups, but no data were given.

· Two trials specifically studied patients with alcoholic cirrhosis. Duration of therapy was unclear in the first, which reported no improvement in laboratory measures of liver function, hepatomegaly, jaundice, ascites, or survival. However, there were nonsignificant trends favoring milk thistle in incidence of encephalopathy and gastrointestinal bleeding and in survival for subjects with concomitant hepatitis C. The second study, after treatment for 30 days, reported significant improvements in aminotransferases but not bilirubin for milk thistle compared with placebo.

· Three trials evaluated milk thistle in the setting of hepatotoxic drugs: one for therapeutic use and two for prophylaxis with milk thistle. Results were mixed among the three trials.

· Exploratory meta-analyses generally showed positive but small and nonsignificant effect sizes and a sprinkling of significant positive effects.

· No studies were identified regarding milk thistle and cholestatic liver disease or primary hepatic malignancy.

· Available evidence does not establish whether effectiveness of milk thistle varies across preparations. One Phase II trial suggested that effectiveness may vary with dose of milk thistle.

Adverse Effects

· Gastrointestinal problems (e.g., nausea, diarrhea, dyspepsia, flatulence, abdominal bloating, abdominal fullness or pain, anorexia, and changes in bowel habits).

However, causality is rarely addressed in available reports. For randomized trials reporting adverse effects, incidence was approximately equal in milk thistle and control groups.

Conclusions

Clinical efficacy of milk thistle is not clearly established. Interpretation of the evidence is hampered by poor study methods and/or poor quality of reporting in publications. Problems in study design include heterogeneity in etiology and extent of liver disease, small sample sizes, and variation in formulation, dosing, and duration of milk thistle therapy.

Possible benefit has been shown most frequently, but not consistently, for improvement in aminotransferases and liver function tests are overwhelmingly the most common outcome measure studied.

Survival and other clinical outcome measures have been studied least often, with both positive and negative findings. Available evidence is not sufficient to suggest whether milk thistle may be more effective for some liver diseases than others or if effectiveness might be related to duration of therapy or chronicity and severity of liver disease.

Regarding adverse effects, little evidence is available regarding causality, but available evidence does suggest that milk thistle is associated with few, and generally minor, adverse effects.

Despite substantial in vitro and animal research, the mechanism of action of milk thistle is not fully defined and may be multifactorial. A systematic review of this evidence to clarify what is known and identify gaps in knowledge would be important to guide design of future studies of the mechanisms of milk thistle and clinical trials.

Future Research

The type, frequency, and severity of adverse effects related to milk thistle preparations should be quantified. Whether adverse effects are specific to dose, particular preparations, or additional herbal ingredients needs elucidation, especially in light of equivalent frequencies of adverse effects in available randomized trials. When adverse effects are reported, concomitant use of other medications and product content analysis should also be reported so that other drugs, excipients, or contaminants may be scrutinized as potential causal factors.

· Detailed data about Systematic standardized surveillance for adverse effects.

· Attention to specific study populations (e.g., patients with hepatitis B virus [HBV], or hepatitis C virus [HCV], or mixed infection or coinfection with human immunodeficiency virus [HIV]), comorbidities, alcohol consumption, and potential confounders.

There also should be detailed attention to preparation, standardization, and bioavailability of different formulations of milk thistle (e.g., standardized silymarin extract and silybin-phosphatidylcholine complex).

Precise mechanisms of action specific to different etiologies and stages of liver disease need explication. Further mechanistic investigations are needed and should be considered before, or in concert with, studies of clinical effectiveness. More information is needed about effectiveness of milk thistle for severe acute ingestion of hepatotoxins, such as occupational exposures, acetaminophen overdose, and amanita poisoning.

Availability of Full Report

Source
Milk Thistle: Effects on Liver Disease and Cirrhosis and Clinical Adverse Effects. Summary, Evidence Report/Technology Assessment: Number 21, September 2000. Agency for Healthcare Research and Quality, Rockville, MD. www.ahrq.gov/clinic/epcsums/milktsum.htm

Milk Thistle & Hepatitis C

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