Milk Thistle - Medicinal Uses, Interactions, Side Effects, Dosage

Milk Thistle
Milk thistle is a member of the Asteraceae or daisy family. Generally, it is the fruit or seed that is used medicinally.
Uses and Benefits:
Milk thistle is typically employed as a hepato-protectanl or to treat established liver disease. This application is based on a long tradition of use for liver, spleen, and biliary disorders. A standardized formulation has been studied by European researchers and promoted for prevention or treatment of all types of liver damago.
Pharmacology:
Milk thistle seeds contain silymarin, a mixturo of three primary flavonolignans: silybin (also known as silybinin or silibinin), silychristin, and silydianin. Silybin is the most abun dant. There are several potential mechanisms by which theso compounds may protect the liver from hepatotoxins, or treat es tablished liver disease.
In vitro, silybin is an antioxidant that reduces lipid peroxidation and scavenges radicals in human platelets, white blood cells, and endothelial cells. These antioxidant properties limit depletion of important endogenous antioxidants such as glutathione and su­peroxide dismutase in vitro and in vivo. This effect has been demonstrated to reduce oxidative damage to liver cells by a vari­ety of different hepatotoxins (e.g., Amanita phalloides mush­rooms, acetaminophen, carbon tetrachloride, and alcohol).
Silybin also strongly inhibits the enzyme 5-lipoxygenase, and thus reduces the formation of inflammatory leukotrienes. The high concentrations required to inhibit cyclo-oxygenase, however, are unlikely to be achieved in clinical practice. Lastly, silybin limits the activity of Kupffer cells in vitro, which may help to slow the progression of chronic liver disease.
Clinical Trials:
In an RCT of drug-induced hepatitis, milk thistle was given to patients with liver disease caused by phenothiazines. A subset of patients also had serology-confirmed hepatitis B. At 90 days, there was no significant change in transaminase levels for patients re­ceiving silymarin or placebo, with or without continuation of psy­chotropic medication. Two RCTs evaluated the use of milk thistle for prophylaxis of drug-induced liver disease. One 8-week, unblinded trial in 172 patients found that significantly fewer patients had elevations of transaminases when a silymarin/Fumaria offici­ na/is herbal combination was administered with antituberculosis drugs, compared to antituberculosis drugs administered alone. In contrast, a 12-week, double-blinded trial in 222 patients ob­served no significant differences in transaminases when silymarin was given in combination with tacrine, compared to tacrine alone.
Case series of intravenous silybin used for Amanita mushroom poisoning have been published in Europe. Typically, the silybin was given in daily doses of 20-50 mg/kg, depending on the disease severity, and in combination with other treatments used at the time such as gastric lavage and penicillin. In general, when silybin was administered within 48 hours of the ingestion and the disease severity was mild to moderate, a benign clinical course was reported. When silybin was administered to patients with severe disease, a decline in mortality was also observed when compared to historical controls. However, prospective controlled trials for this use have not been published.
Adverse Effects:
No major side effects have been reported for patients using milk thistle. Loose stools and other mild gastrointestinal effects occur rarely.
Side Effects and Interactions:
There are no reported drug interactions with milk thistle. Silybin does not interact with most hepatic cytochrome P450 (CYP) enzyme systems, but inhibition of CYP3A4 (as well as UGT1A6/9 and possibly CYP2C9) enzymes has been demonstrated in several in vitro studies. Caution is thus warranted in using the herbs in combination with other drugs metabolized in the liver.
Cautions:
People with allergies to plants of the Asteraceae family(e.g., daisy, sunflower, chrysanthemum, ragweed) may be allergic to milk thistle as well. Milk thistle's safety in pregnant and breast-feeding women has not been established.
Preparations & Doses:
A daily dose of 200-400 mg of silymarin in 2-3 divided doses is usually recommended; this range of dosage was employed in the clinical trials. Milk thistle products are usually standardized to contain no less than 70-80% silymarin. The product used in most of the European trials, Legalon, is marketed in the U.S. as Thisylin (Nature's Way). Silipide, or IdB 1016, a silymarin-phosphatidylcholine complex that has enhanced bioavailability, is not marketed in the U.S.
Summary Evaluation
The efficacy of milk thistle in alleviating symptoms of viral and alleviating related liver disease is not established. Improved liver Ilansaminases and improved survival in mild alcoholic liver discount have been demonstrated in limited studies, but are not tently found among the many clinical trials. It is doubtful that thistle is beneficial in severe liver disease such as cirrhosis. Ophylactic use of milk thistle to protect the liver against hepato xins (e.g., alcohol) is based primarily on laboratory and animal (fata, with inadequate clinical evidence. Milk thistle has not been i:Ompared with interferon or other pharmaceutical options for viral epatitis, nor has an effect on viral loads been evaluated. Although dinically relevant benefits are not clearly established, because thistle has no major side effects and there is a lack of well­lolerated orthodox drugs, it is tempting for patients to try milk this­lie for preventing or treating established liver disease. If used, efficacy can be monitored with appropriate laboratory testing.

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