HERBS and their interactions with drugs are high yield on USMLE Step3.
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.
Unlike conventional drugs, herbal products are not regulated for purity and potency. 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 effects.
Ginkgo Biloba : The active ingredients in Ginkgo biloba extract account for its antioxidant properties and its ability to inhibit platelet aggregation. Consequently, this herbal product is promoted for use in improving cognitive function and blood flow. To date, however, at least four reports of spontaneous bleeding in association with use of Ginkgo biloba.
Ginkgo biloba………..> Bleeding
St. John’s wort……….> Gastrointestinal disturbances, allergic reactions, fatigue, dizziness, confusion, dry mouth, photosensitivity , Interaction with Red Wine.
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
Ginkgo biloba……..> Aspirin, warfarin (Coumadin), ticlopidine (Ticlid), clopidogrel (Plavix), dipyridamole (Persantine)
St. John’s wort……..> Antidepressants
Ephedra………………> Caffeine, decongestants, stimulants
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. 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.
Ephedra : - Ephedrine and related alkaloids are the pharmacologically active moieties of the extract of Ephedra (a genus of shrubs). 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 aalternative to the use of fenfluramine (Pondimin) and dexfenfluramine (Redux). Ephedrine-containing products are also marketed as decongestants, bronchodilators and stimulants. 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. 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. 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.
Ginseng : -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.
Kava :- Kava is an herbal sedative with purported antianxiety or calming effects. In one case series involving four patients, kava was associated with extrapyramidal effects at dosages of 100 to 450 mg per day. 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. example : A patient taking alprazolam (Xanax), cimetidine (Tagamet) and terazosin (Hytrin) became lethargic and disoriented after ingesting kava. Kava should not be used with benzodiazepines.