Written by PhytoPharmica
(reprinted with permission)

Question
I have an 8 1/2 year old Rottweiler that has been on Phenobarbital since the age of 4. Recently he became quite ill and the veterinarian said his liver was failing due to the Phenobarbital use. We began giving him Super Thistle X three times a day, and over time he greatly improved. He seems to be his old self again! We are now giving him 2 capsules a day in order to keep this from happening again. [snip] I do not expect you to be an expert on dogs, but could you give me any information on long-term milk thistle use? Is there any research on the use of milk thistle in dogs? Are there any disorders that would benefit from the use of daily milk thistle?

Answer
RESEARCH IN DOGS
The majority of information and research on milk thistle and a key component, silymarin, refers to human use. There are studies that used dogs as laboratory animals to test the physiological activity of silymarin, but these studies were conducted with the goal of applying any information gained on subsequent human use.(1,2) Therefore, we cannot answer this question with absolute certainty due to the lack of canine specific research. We encourage anyone interested in using human nutritional supplements for their pets to do so with the advice and oversight of their veterinarian.

LONG-TERM USE
The German Commission E Monographs listing for milk thistle fruit lists no contradictions and no dosage time limits. The only side effect listed is an occasional mild laxative effect.(3) The PDR for Herbal Medicines also lists no dosage time limits, no side effects, and no contradictions.(4) In a 1989 study, 87 patients with cirrhosis received 140mg silymarin three times a day for an average of 41 months. No side effects of silymarin treatment were observed.(5) In a more recent study, 30 patients with both diabetes and alcoholic cirrhosis received 600mg silymarin per day for 12 months. No adverse effects were reported.

BENEFITS OF MILK THISTLE
Research on milk thistle and it's components appears to be growing, given the volumes of abstracts listed on MEDLINE.(7) The current theory regarding mode of activity is that silymarin supports liver health in two major ways. First, it alters the outer cell membrane of hepatocytes (liver cells) in such a way as to prevent penetration of harmful substances into the interior of cells. Second, it stimulates the action of nucleolar polymerase A (an enzyme involved in chromosome replication) resulting in an increase in ribosomal protein synthesis, which stimulates the regenerative ability of the liver and the formation of new hepatocytes. Silymarin may also stimulate an increase in bile flow from the gall bladder to the intestine.(4) Silymarin is being investigated as an agent to support healthy cholesterol levels by exerting an effect on the liver cholesterol metabolism. Silymarin also possesses antioxident properties. (9) Studies have indicated that oxidative stress plays a role in the pathogenisis of toxic liver disease and other liver problems, and silymarin may reduce oxidative stress in the liver. (10) Therefore, any liver subjected to chemical or chronic illness stresses may benefit from the additional nutritional support that silymarin provides. In an article for Prevention magazine, Varro Tyler, Ph.D., Sc.D, states that milk thistle may help support the liver in people taking prescription medication that may adversely affect the liver.

We were unable to locate any published studies that indicated that silymarin was contradicted in persons with liver damage and/or liver illness. We were also unable to find any published studies that indicated adverse effects with long-term use of milk thistle in humans.

REFERENCES
1. Paulova J, Dvorak M, Kolouch F, Vanova L, Janeckova L. Verification of the hepatoprotective and therapeutic effect of silymarin in experimental liver injury with tetrachloromethane in dogs. VetMed(Praha). 1990;35:629-635. Abstract
2. Vogel G, Tuchweber B, Trost W, Mengs U. Protection by silibinin against Amanita Phalloides intoxication in beagles. Toxicol Appl Pharmacol. 1984;73:355-362 Abstract
3. Milk thistle fruit. In: Blumenthal M., ed. The Complete German Commision E Monographs. Austin, Tex; American Botanical Council; Integrative Medicine Communications; 1998: 169-170
4. Silybum marianum. In: Fleming T, ed. PDRr for Herbal Medicines. Montvale, NJ: Medical Economics Company; 1998: 1138-1141
5. FerenciP, Dragosics B, Dittrich H, et al. Randomized controlled trial of silymarin treatment in patients with cirrhosis of the liver. Jhepatol. 1998;9:105-113 Abstract
6. Velussa M, Cernogoi AM, De Monte A, Dapas F, Caffau C, Zilli M. Long-term (12 months) treatment with an anti-oxidant drug (silymarin) is effective on hyperinsulinemia, exogeneous insulin need and malondialehyde levels in cirrhotic diabetic patients.Jhepatol. 1997;26:871-879. Abstract
7. MEDLINE. Electronic database for the National Library of Medicine. Available at: MedLine
8. Skottovs N, Krecman V. Silymarin as a potential hypocholesterolaemic drug. Physiol Res. 1998;47:1-7. Abstract
9. Ahmad N, Gali H, Javed S, Agarwal R, Skin cancer chemoprotective effects of a flavonoid antioxidant silymarin are mediated via impairment of receptor tyosine kinase signaling and perturbation in cell cycle progression. Biochem Biopphys Res Commun. 1998;18:294-301 Abstract
10. Feher J, Lengyel G, Blazovics A. Oxidative stress in the liver and biliary tract diseases. Scand J Gastroenterol Suppl. 1998;228:38-46
11. Tyler VE. This Weed is a Potent Healer. Prevention. 1998; 79-82

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