Milk Thistle

Effects On Enzymes And Transporters

UGT Enzyme	Effects	Strength	Dosage	Verified in Man
UGT1A1	No Effect1 [5]	?	200 mg 3 times a day	Yes
UGT1A6	Inhibition [2]	IC50 59.5 μg/ml	?	?
UGT1A9	Inhibition [2]	IC50 33.6 μg/ml	?	?
UGT2B7	Inhibition [3]	?	?	?
P450 Enzyme	Effects	Strength	Dosage	Verified in Man
CYP2C9	Inhibition and possible induction2	?	?	?
CYP2D6	No effect [1]	?	?	Yes
CYP3A4	No effect [5]	?	200 mg 3 times a day	Yes
Transporter	Effects	Strength	Dosage	Verified in Man
P-Glycoprotein (Pgp)	Inhibition [4]	?	?	?

Bibliography

1. Clinical assessment of CYP2D6-mediated herb-drug interactions in humans: effects of milk thistle, black cohosh, goldenseal, kava kava, St. John's wort, and Echinacea.

Gurley BJ, Swain A, Hubbard MA, Williams DK, Barone G, Hartsfield F, Tong Y, Carrier DJ, Cheboyina S, Battu SK; PubMed PMID 18214849

2. Inhibitory effects of commonly used herbal extracts on UDP-glucuronosyltransferase 1A4, 1A6, and 1A9 enzyme activities.

Mohamed ME, Frye RF. PubMed: PMID: 21632963

3. Effects of herbal supplements on drug glucuronidation. Review of clinical, animal, and in vitro studies.

Mohamed ME, Frye RF. PubMed: PMID: 21049395

4. Emerging Significance of Flavonoids as P-Glycoprotein Inhibitors in

Cancer Chemotherapy Tripta Bansal, Manu Jaggi, Roop K Khar and Sushama Talegaonkar; J Pharm Pharmaceut Sci (www. cspsCanada.org) 12 (1): 46 - 78, 2009 (Download Attached PDF Document)

5. Effect of milk thistle (Silybum marianum) on the pharmacokinetics of irinotecan.

van Erp NP, Baker SD, Zhao M, Rudek MA, Guchelaar HJ, Nortier JW, Sparreboom A, Gelderblom H. PubMed PMID: 16278402

Footnotes

1. 200 mg of milk thistle does not contain enough silybin to effectively inhibit UGT1A1.

2. Milk thistle activates PXR in vitro which may lead to CYP2C9 induction.