Warning About interactions Between Milk Thistle and Drugs

[liverock]

An in vitro study has shown that Milk Thistle had interactions with several drugs, particularly some HIV drugs, due to it blocking an enzyme in the liver which controls a detoxification pathway. This can cause a buildup of the drug in the system and an increase in side effects.

http://www.hcvadvocate.org/news/News...s/mthistle.pdf

A WARNING ABOUT MILK THISTLE AND DRUGS

The seeds of the milk thistle plant are commonly used to protect the liver from damage caused by hepatitis
viruses as well as alcohol and other substances. Compounds found in milk thistle sylibin, sylimarin act as antioxidants and also stimulate the repair of the liver. But now it appears that these and possibly other compounds in milk thistle can have other effects.


Researchers at the University of Pittsburgh have suspected that milk thistle can slow down or reduce the activity of enzymes in the liver. What does this have to do with HIV? you might ask. Well, enzymes in the liver break down many of the substances that we eat and drink, including medications. If the activity of these enzymes are reduced, then drugs remain in the blood longer than they otherwise might. This could lead to having higher-than-expected levels of drugs in the body, causing side effects or intensifying already-existing side effects. Indeed, in recent experiments using milk thistle and human liver cells, the researchers found that relatively small concentrations of milk thistle did significantly slow down the activity of the liver enzyme CYP3A4 by 50% to 100%.


Many medications taken by people with HIV/AIDS (PHAs) such as protease inhibitors and non-nukes are processed by this liver enzyme. If milk thistle is taken by someone using protease inhibitors or non-nukes, it has the potential to raise levels of these drugs, causing unpleasant or even dangerous side effects.


Below is a short list of some other medications that are processed through the CYP3A4 enzyme.


Levels of these medications may increase if taken by people who are also using milk thistle. This list is not exhaustive:

methadone
heart drugs – Tambocor (flecainide), Rythmol (propafenone)
antibiotics – erythromycin, rifampin
anti-seizure drugs – carbamazepine (Tegretol)
antidepressants – St. John's wort, Zyban/Wellbutrin (bupropion), Paxil (paroxetine), Prozac
(fluoxetine), Luvox (fluvoxetine) Serzone (nefazodone), Zoloft (sertraline), Effexor (venlafaxine)
antihistamines – Hismanal (astemizole), Seldane (terfenadine)
antifungals – itraconazole (Sporanox), Ketoconazole (Nizoral)
gastrointestinal motility agents – Prepulsid (Cisapride)
ergot drugs – Ergonovine, Ergomar (ergotamine)
anti-psychotics – Clozaril (clozapine), Orap (pimozide)
sedatives/sleeping pills – Ambien (zolpidem), Halcion (triazolam), Versed (midazolam)
lipid-lowering drugs (statins) – Lescol (fluvastatin), Mevacor (lovastatin), Pravachol (pravastatin) and
Zocor (simvastatin), Baycol (cerivastatin)
transplant drugs – cyclosporine (Neoral, Sandimmune), ProGraf (tacrolimus)

Milk thistle also has the potential to lower levels of the following drugs:

anti-parasite drugs – Mepron (atovaquone)
sedatives/sleeping pills – Ativan (lorazepam)
hormones – estrogen


The research by the scientists in Pittsburgh should emphasize to readers that simply because a product is "natural" it does not mean it is safe when taken wisubstances. This research also shows the need to conduct further research on herb-drug interactions on liver cells as well as in people. Such studies may find combinations of herbs and drugs that can be safely used together.

The Pittsburgh researchers noted that "patients and health care professionals must be encouraged to
discuss the use of herbs and be educated about the potential interactions between herbs and drugs." This cannot be stressed enough.


REFERENCE
Venkataramanan R, Ramachandran V, Komoroski BJ, et al. Milk thistle, a herbal supplement, decreases the
activity of CYP3A4 and uridine diphosphoglucuronosyl transferase in human hepatocyte cultures. Drug

Metabolism and Disposition 2000;28(11):1270-1273.

 

[illsince1977]

Thanks for posting this.

All I'd ever heard was that milk thistle is good for your liver. Is it possibly "good" for your liver by keeping it from working so hard? Wouldn't that in turn make it bad for your body by slowing detox? Might that be why I started getting bad headaches after taking it for a few months? I only realized milk thistle was causing them when out of desperation to figure out what was causing them, I stopped and they went away 2 days later.

At least I wasn't taking milk thistle when I was taking Mepron!

A lot has been written about grapefruit effecting the same pathway, but I had no idea milk thistle does too.

This just reinforces my new found conviction not to use supplements. I don't do well on them at all. It's obvious to me now that their mechanisms are even less studied than drug mechanisms, which are poorly understood as it is! You've given me a whole new perspective on it! Thanks.

-Susan

 

[Lotus97]

Indeed, in recent experiments using milk thistle and human liver cells, the researchers found that relatively small concentrations of milk thistle did significantly slow down the activity of the liver enzyme CYP3A4 by 50% to 100%.

This is interesting. I assumed that milk thistle increases cytochrome p450 cyp3a4 enzymes since it is recommended for detoxification, but I guess not

 

[Lotus97]

I found something that suggests milk thistle might not inhibit cyp3a4 to a significant amount.
http://www.cancer.gov/cancertopics/pdq/cam/milkthistle/HealthProfessional/page6

Silymarin decreases the activity of the cytochrome P450 enzyme system, which is involved in the clearance of certain chemotherapy drugs.[6] However, the dose at which inhibition is observed is high and not achieved with oral intake of silymarin.[7] One study investigated the effects of silymarin on the pharmacokinetics of irinotecan. Oral administration of milk thistle (200 mg, a clinically relevant dose, 3 times per day) had no significant effects on the pharmacokinetics of irinotecan. The authors concluded that the recommended doses of milk thistle are too low to affect activity of CYP3A4 or UGT1A1 enzyme pathways.[8]

 

[alex3619]

Its not just drugs. If you have high iron levels, milk thistle has been claimed to exercabate the effects. I have not investigated this to confirm it, but I avoid milk thistle as a precautionary measure since my iron levels are high.

 

[Lotus97]

Its not just drugs. If you have high iron levels, milk thistle has been claimed to exercabate the effects. I have not investigated this to confirm it, but I avoid milk thistle as a precautionary measure since my iron levels are high.

I just read that milk thistle chelates iron so I thought that it would be good if you have too much iron, but I guess if you don't have anything to bind to the iron that's chelated you wouldn't be able to eliminate the iron and it would be redistributed back into your tissues. This is an issue with chelation in general which a lot of people seem to overlook.

 

[alex3619]

Yes Lotus97, there is no natural pathway to elimate iron except bleeding. You just move it around.