Epilepsy Ontario :: Herbal Therapies for Epilepsy

Herbal Therapies for Epilepsy: Herb-Drug Interactions

by Erica Tennenhouse
The use of herbal medications has dramatically increased over the past few years. Approximately 18% of people who take prescription drugs also use herbal supplements (1). Herbal medicines are classified by the Food and Drug Administration (FDA) as dietary supplements rather than drugs, which means that the FDA requires no regulations regarding the efficacy and safety of herbs (2). However, drug metabolizing enzyme systems in the body process compounds that are ingested, including herbal medications. This means when herbal medications are all taken in combination with prescribed antiepileptic drugs (AEDs), there is the potential for harmful herb-drug interactions to occur.

Certain herbs produce effects similar to those of some AEDs. When these herbs and AEDs are used concurrently, their effects become magnified. Kava mimics the effects of phenobarbital and benzodiazepines by slowing down brain activity (1). It also reduces the electrical excitability of brain cells in a similar manner to carbamazepine and phenytoin. Thus, taking kava along with any of these medications could cause excessive sedation and clouded thinking. Valerian exhibits additive effects similar to kava when taken in combination with barbiturates and benzodiazepines. Passionflower has an active ingredient called chrystin, which produces effects that mimic benzodiazepines such as diazepam and alpraxolam, and could magnify their sedative effects.

Some herbs can affect the system that is responsible for the enzymatic breakdown of AEDs in the liver - the P450 system (3). If an herb has the effect of exciting the P450 system, this means that AEDs will be broken down faster than normal, and will therefore be less effective. On the other hand, if an herb inhibits the P450 system, it will slow down the break down of AEDs, and AEDs will remain in the body for longer than they should. St. John's wort increases the liver metabolism of AEDs as well as other drugs. For example, it can affect warfarin, which is used to prevent blood clotting, cyclosporine, which is used to prevent transplant rejection, and indinavir, which is used in the treatment of HIV (4). St. John's wort can also lower the levels of AEDs such as phenytoin and phenobarbital (5). Garlic and Echinacea have the effect of inhibiting the liver metabolism of AEDs, thus increasing the bioavailability of AEDs in the system.

Some herbs actually increase the likelihood of seizures by stimulating brain activity. The main ingredient in ephedra is ephedrine, which is very similar in structure to amphetamines (stimulants). Ephedra stimulates the brain and may worsen seizures, or cause seizures where no past history of seizures existed, if taken in combination with other stimulants (6). Herbs containing caffeine stimulate the release of neurotransmitters in the brain, causing high levels of brain activity. Therefore, people with seizures should avoid caffeine, or minimize their caffeine consumption. Ginkgo is used by many people daily, usually as a therapy to improve memory; however, the FDA has received several reports of people having seizures after taking it (6). It is probably safer for people with epilepsy to avoid ginkgo until more research on its effect has been conducted. Some other herbs that may cause seizures are: ginseng, evening primrose, borage, and essential oils such as eucalyptus, fennel, hyssop, pennyroyal, rosemary, sage, savin, tansy, thuja, turpentine, and wormwood (4).

There are many potential interactions between herbs and prescription drugs, only a few of which are discussed in this article, and often these interactions are quite complex. Herb-drug interactions can cause magnification of the effects of AEDs, increase or decrease in the metabolism of AEDs, and induction of seizures. On the other hand, many herbal supplements do exhibit anticonvulsant properties, and may provide epilepsy patients with some relief from seizures. However, herbs should be carefully researched before being used as supplements or medical therapies to treat epilepsy. Patients and physicians should understand that a complete medication history must include a list of herbal supplements that are being taken.

Sources
1. Bressler R. Herb-drug interactions: Interactions between Kava and prescription medications. Geriatrics. 2005. 60:24-25.
2. Angell M and JP Kassirer. Alternative medicine: the risks of untested and unregulated remedies. New England Journal of Medicine. 1998. 339:839-841.
3. Conry, JA. et al. "Herbal Therapy in Epilepsy." Devinsky, Schachter, and Pacia. 129-142.
4. Luciano, DJ and Marcello Spinella. "Herbal Treatment of Epilepsy: Phytotherapy." Devinsky, Schachter, and Pacia. 143-155.
5. Bressler R. Herb-drug interactions: Interactions between St. John's wort and prescription medications. Geriatrics. 2005. 60:21-23.
6. Tyaga, Alok and Norman Delanty. Herbal Remedies, Dietary Supplements, and Seizures. Epilepsia. 2003. 44:228-235.
7. Devinsky, Oren, Steven Schachter, and Steven Pacia, eds. Complementary and Alternative Therapies for Epilepsy. New York: Demos Medical Publishing, 2005.