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Adverse Effects and Drug Interactions of Herbal Remedies

Approximately 25 percent of Americans who consult their physician about a serious health problem are employing unconventional therapy, but only 70 percent of these patients inform their physician of such use.1

Unlike conventional drugs, herbal products are not regulated for purity and potency.2 Thus, some of the adverse effects and drug interactions reported for herbal products could be caused by impurities (e.g., allergens, pollen and spores) or batch-to-batch variability. In addition, the potency of an herbal product may increase the possibility of adverse herbs, herbal, herb, remedies, ginko biloba home remedies

Ginkgo Biloba

The active ingredients in Ginkgo biloba extract account for its antioxidant properties and its ability to inhibit platelet aggregation.3 Consequently, this herbal product is promoted for use in improving cognitive function and blood flow.4 To date, however, at least four reports of spontaneous bleeding in association with use of Ginkgo biloba have been

One report4 described a Over a three-month follow-up period, he had no further bleeding episodes. Interaction of the ginkgo product and aspirin was considered the cause of his ocular herbs, herbal, herb, remedies, home remedies, natural ginko biloba


Side Effects of Select Herbal Products

Herbal product
Side effects
Ginkgo biloba Bleeding
St. John's wort Gastrointestinal disturbances, allergic reactions, fatigue, dizziness, confusion, dry mouth, photosensitivity
Ephedra (ma huang) Hypertension, insomnia, arrhythmia, nervousness, tremor, headache, seizure, cerebrovascular event, myocardial infarction, kidney stones
Kava Sedation, oral and lingual dyskinesia, torticollis, oculogyric crisis, exacerbation of Parkinson's disease, painful twisting movements of the trunk, rash
Drug Interactions with Herbal Products

Herbal product
Interacting drugs
Ginkgo biloba Aspirin, warfarin (Coumadin), ticlopidine (Ticlid), clopidogrel (Plavix), dipyridamole (Persantine)
St. John's wort Antidepressants
Ephedra Caffeine, decongestants, stimulants
Ginseng Warfarin
Kava Sedatives, sleeping pills, antipsychotics, alcohol


Ginkgo biloba may also interact with warfarin (Coumadin). A 78-year-old woman who had been taking warfarin for five years after coronary bypass surgery suffered a left parietal hemorrhage after using a ginkgo product for two months.5 No change was noted in her prothrombin time. The intracerebral bleeding was attributed to the antiplatelet effects of ginkgo.

St. John's Wort

St. John's wort (Hypericum perforatum) is an herb widely promoted as a "natural" antidepressant.9 In Germany, this herb is commonly prescribed for various psychopathologic conditions involving depression and anxiety. Herbal products are permitted to be marketed in Germany if they fit general criteria in published monographs.10 However, the safety and efficacy of St. John's wort are not


Ephedrine and related alkaloids are the pharmacologically active moieties of the extract of Ephedra (a genus of shrubs).19 Ephedrine constitutes 30 to 90 percent of the alkaloids of Ephedra species. The extract of some species also contains pseudoephedrine.

Ephedra (ma huang) is commonly found in herbal weight-loss products referred to as "herbal fen-phen." Some weight loss clinics and retail outlets promote herbal products as an alternative to the use of fenfluramine (Pondimin) and dexfenfluramine (Redux), the prescription anorexiants recently removed

Ephedrine-containing products are also marketed as decongestants, bronchodilators and stimulants.21 Other promoted uses include enhancement of athletic performance and body-building efforts. Marketed uses of ephedrine-containing products such as "herbal ecstasy" include induction of a euphoric state

Ephedra-containing products have also been associated with the development of kidney stones. Ephedrine, pseudoephedrine and metabolites comprised almost 100 percent of a radiolucent stone removed from a 27-year-old male body builder who took up to 12 Pro-Lift tablets daily. Each tablet was found to contain approximately 10 mg of ephedrine. Information from a large kidney stone database shows that this is not an isolated incident; over 100 ephedrine-containing kidney stones were identified from January 2002 to June 2002. It is not known how many of these stones were associated with the use of herbal ephedrine-containing products.26

The risks of using ephedrine-containing supplements appear to outweigh the benefits. Consequently, patients should be advised not to use these products if they are sensitive to the effects of sympathomimetic agents.21 Such patients include those with hypertension, hyperthyroidism, diabetes mellitus, psychiatric conditions, glaucoma, prostate enlargement, seizure disorders and cardiovascular disease. Concomitant use of ephedrine-containing products and caffeine or other stimulants should also be discouraged.


Little scientific evidence shows that ginseng is effective for any purpose. Nonetheless, this herb has been purported to strengthen normal body functions, increase resistance to stress and improve sexual


Kava is an herbal sedative with purported antianxiety or calming effects. In one case series involving four patients,29 kava was associated with extrapyramidal effects at dosages of 100 to 450 mg per day. Symptoms occurred 90 minutes after one patient took a single 100-mg dose, four hours after one patient took a single 100-mg dose, four days after one patient began taking 150 mg three times daily, and 10 days after one patient began taking 150 mg twice daily. The extrapyramidal side effects included oral and lingual dyskinesia, torticollis, painful twisting movements of the trunk, oculogyric crisis and exacerbation of Parkinson's disease.

Kava has also been shown to have additive effects with central nervous system depressants. A patient who was taking alprazolam (Xanax), cimetidine (Tagamet) and terazosin (Hytrin) became lethargic and disoriented after ingesting kava.30

Kava should not be used with benzodiazepines,