Herb-Drug Interactions

When herbal therapies and drugs (prescription or non-prescription medications) are used together, they can interact in your body, causing changes in the way the herbs and/or the drugs work. Such changes are called herb-drug interactions.

Herb-drug interactions can impact your health and the effectiveness of your treatments. For example, some herbal therapies might:

• Increase the side effects of drugs, possibly leading to toxicity.
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• Decrease the therapeutic effect of drugs, possibly leading to treatment failure. (In the case of highly active antiretroviral therapy [HAART], such an interaction can also cause drug resistance, thereby limiting future options for treatment.)

• Modify the action of drugs, possibly leading to unexpected complications.

• Enhance the therapeutic effect of drugs, possibly leading to over medication.

Likewise, prescription and non-prescription drugs can alter the way your body reacts to herbal therapies.

Listing all of the herb-drug interactions, which potentially impact people living with HIV/AIDS, is not possible. Here are only a few important interactions of which you should be aware.

General Interactions

PHAs should be cautious about mixing herbs and drugs in any of the following situations:

• The herbal therapy can change digestion, and kidney or liver functions.

• The herbal therapy is reported to have similar side effects to the drug therapy.

• The herbal therapy and the drug therapy are used to treat the same condition.

• There is underlying impairment or damage to the stomach, liver or kidney as a result of illness or adverse drug reactions.

Highly Active Antiretroviral Therapy (HAART)

The following combinations should not be taken together

• St. John's Wort (Hypericum perforatum) with any protease inhibitor or any non-nucleoside reverse transcriptase inhibitor (NNRTI).

• Large quantities of raw or processed garlic with any protease inhibitor (a few cloves of cooked garlic in food should not be a problem).

The following combinations might alter levels of antiretroviral drugs in the blood

• Milk thistle with any protease inhibitor or any non-nucleoside reverse transcriptase inhibitor (NNRTI).

Other Drugs

Many PHAs are taking other medications in addition to HAART. These can include antibiotics, medications for high blood pressure, depression, heart conditions and diabetes, to name a few. The following herb-drug combinations have the potential for significant interactions. This list is not exhaustive.

• Ginko biloba with anticoagulants.

• St. John Wort (Hypericum perforatum) with antidepressants, oral contraceptives, anticoagulants and transplant medications.

• Kava Kava (Piper methysticum) with alcohol or liver damage.

• Devil's Claw (Harpagophytum procumbens), Ginseng (Panax ginseng) or Dong Quai (Angelica sinensis) with warfarin.

• Hawthorn (CrataegusSpecies) with antihypertensive medications, digoxin or antidepressants.

When combining herbal therapies with other medications, it is important to watch for potential interactions. Informing all your health care providers (doctors, nurses, pharmacists and complementary practitioners) about all the herbal therapies and medications you are taking can help reduce the risk of harmful interactions. For more information on herb-drug interactions, please read CATIE's fact sheet called Herb-Drug Interactions, available at www.catie.ca or by calling 1-800-263-1638.