(for veterinary information only)

(MILK THISTLE)

Numerous herbal brands are available (usually as seed extract)

BACKGROUND

Milk thistle is a flower, more specifically  a member of the aster family. Its seeds and roots have been used for an assortment of medical purposes  for thousands of years. Three biochemicals of interest have been isolated from the milk thistle: silychristine, silydianin, and silybin. The mixture of these three substances is called “silymarin.”  Silymarin has been traditionally used in the treatment of liver disease  and, while it has recently been advocated for use in pets, all scientific information available concerns human use. The biological mechanism of action is yet unknown but several theories exist:

• Silymarin may control cell membrane permeability which means that silymarin may control what substances actually enter the interior of a cell.
   
• Silymarin may inhibit chemical pathways  leading to inflammatory biochemicals.
   
• Silymarin may have free radical scavenging properties which means that it may absorb harmful reactive atoms that could damage  other molecules.
   
• Silymarin may increase protein production by liver cells.
   
• Silymarin may stabilize mast cells (cells containing inflammatory  granules).
   
• Silymarin in higher doses  increases the flow of bile.

HOW THIS MEDICATION IS USED

The most scientific information concerning the use of silymarin regards Amanita mushroom poisoning. Silymarin prevents uptake of the poison into the cells of the liver and  thus prevent the lethal liver damage associated with this type of mushroom poisoning.

Silymarin is regularly used for an assortment of liver diseases including cirrhosis and viral hepatitis in humans. The only actual studies conducted in dogs have concerned mushroom poisoning as above and other uses in pet species are inferred from human use. Milk thistle extracts appear to be safe to use; however, their benefit is not well defined scientifically.

SIDE EFFECTS

At doses greater than 1.5 grams per day  the increased bile flow side effect may cause diarrhea. Side effects are very rare but the following has been reported for humans: upset stomach, headache, joint pain, weakness.

INTERACTIONS WITH OTHER DRUGS

While there are no known drug interactions, it is important to remember that herbal medications are not held to the same standards of efficacy and safety that other drugs are. Impurities in processing  may include less innocuous plant biochemicals.

CONCERNS AND CAUTIONS

Silymarin is not recommended for humans during pregnancy. It is probably a good idea not to use milk thistle products in pregnant dogs until more information becomes available.

Milk thistle products should be stored at room temperature.

Because herbal medications are not held to the same purity and efficacy standards as other medications, there may tremendous variation in strength between brands or even between batches of the same brand.