Nearly 20% of patients who take prescription drugs also take herbal supplements. Unlike drugs, herbal therapies are classified by the FDA as dietary supplements and are not subject to regulations concerning their preparation, safety, or effectiveness.
Herbal therapies are prepared from the flowers, leaves, stems, bark, or roots of plants. Some of these can be taken directly, but others undergo various forms of processing, such as drying of bark. Herbal therapy is ancient, dating back to prehistoric times. Many modern drugs are derived from plants of herbal therapy. Texts from the 18th and 19th centuries describe many herbal therapies for epilepsy, including mistletoe, foxglove (digitalis), and Cannabis sativa (marijuana), but few were found to be of much help.
A common misconception is that if a substance is synthetic it is unsafe, but if it is natural, it is safe. Hemlock and poisonous mushrooms illustrate that plants can be deadly.
Herbal preparations are most often recommended to treat epilepsy in Asian or African folk medicine practices. The herbal medicines that are alleged, but not proven, to have a beneficial effect on seizures include:
Most of them are relatively safe in recommended doses, but adverse effects include rash, digestive disturbances, and headache. However, overdoses can be dangerous.
In isolated cases, some herbal products were reported to cause seizures: ephedra, gingko, ginseng, evening primrose, borage, and essential oils such as eucalyptus, fennel, hyssop, pennyroyal, rosemary, sage, savin, tansy, thuja, turpentine, and wormwood. The exact mechanism of how these drugs may induce seizures is not known. Gingko may reduce the effectiveness of antiepileptic drugs.
Herbal therapies can interact with antiepileptic drugs. For example, St John’s Wort can lower levels of certain antiepileptic drugs, including phenobarbital and phenytoin. Garlic may increase the levels of some antiepileptic drugs. Chamomile may intensify or prolong the effects of phenobarbital. Sedating herbs such as kava, valerian and passionflower can increase sedation produced by phenobarbital, benzodiazepines, and other drugs.