The mechanisms of action of
silymarin involve different biochemical events, such as the stimulation of the synthetic rate of
ribosomal RNA (rRNA) species through stimulation of polymerase I and rRNA transcription, protecting the cell membrane from radical-induced damage and blockage of the uptake of toxins such as
alpha-amanitin. Studies in patients with
liver disease have shown that
silymarin increases
superoxide dismutase (SOD) activity of lymphocytes and erythrocytes, as well as the expression of SOD in lymphocytes.
Silymarin has also been shown to increase patient serum levels of
glutathione and
glutathione peroxidase.
Silybin 20 to 48 mg/kg/day has shown promise as a clinical
antidote to acute Amanita (deathcap
mushroom) poisoning. Primary efficacy data from 3 trials which examined the therapeutic potential of
silymarin in patients with
cirrhosis, and included patient survival as an end-point, demonstrated that
silymarin had no significant beneficial effect on patient mortality. However, upon subanalysis,
silymarin 420 mg/day had a significantly beneficial effect on patient survival rate (compared with patients receiving placebo) in 1 randomised, double-blind trial in patients with
alcoholic cirrhosis.
Silymarin 420 mg/day was also shown to improve indices of liver function [AST, ALT, gamma-glutamyl
transferase and
bilirubin] in patients with
liver disease of various aetiology, including those exposed to toxic levels of
toluene or
xylene; however, it was largely ineffective in patients with viral
hepatitis. Reports of adverse events while receiving
silymarin therapy are rare. However, there have been accounts of
nausea, epigastric discomfort,
arthralgia,
pruritus,
headache and
urticaria.
Silymarin has also been reported to have possibly caused a mild
laxative effect.
CONCLUSION: The
antioxidant properties of
silymarin (a mixture of at least 4 closely related
flavonolignans, 60 to 70% of which is a mixture of 2 diastereomers of
silybin) have been demonstrated in vitro and in animal and human studies. However, studies evaluating relevant health outcomes associated with these properties are lacking. Although
silymarin has low oral absorption, oral dosages of 420 mg/day have shown some therapeutic potential, with good tolerability, in the treatment of
alcoholic cirrhosis. Moreover,
silybin 20 to 48 mg/kg/day has shown promise as an
antidote for acute
mushroom poisoning by Amanita phalloides; however, further studies paying attention to the amount of ingested mushroom and time elapsed before administration of treatment are needed to clarify its role in this indication. Studies in patients with the early onset of
liver disease may demonstrate the liver regeneration properties that
silymarin is promoted as possessing.