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.
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