A warning about milk thistle and drug interactions

[Guest guest]

HCV Advocate 12/13/01

A warning about milk thistle and drug interactions

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. '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 with

other substances. 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.

This information was provided by the Community AIDS

Treatment Information Exchange (CATIE). For more

information, contact CATIE at 1-800-263-1638.

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