Interactions

Interactions with Drugs

St. John's wort may interfere with the way the body processes various drugs using the liver's "cytochrome P450" enzyme system. As a result, the levels of these drugs may be increased in the blood (causing increased effects or adverse reactions) or decreased in the blood (which may reduce effects). Examples of medications that may be affected by St. John's wort in this manner include carbamazepine, cyclosporin, irinotecan, midazolam, nifedipine, simvastatin, theophylline, warfarin, or HIV drugs such as non-nucleoside reverse transcriptase inhibitors (NNRTIs) or protease inhibitors (PIs). The U.S. Food & Drug Administration (FDA) suggests that patients with HIV/AIDS taking PIs or NNRTIs should avoid taking St. John's wort.

St. John's wort may alter the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

St. John's wort may alter blood sugar levels. Caution is advised when using medications that may also alter blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

St. John's wort may affect blood pressure. Caution is advised in people taking drugs that affect blood pressure.

St. John's wort may also interact with 5HT1 agonists (triptans), agents for the eyes, agents for the skin, agents for the stomach and intestines, agents that affect the nervous system, agents that affect the immune system, agents that damage the liver, anesthetics, alcohol, anti-anxiety agents, antibiotics, antidepressant agents, antifungals, antihistamines, anti-inflammatory agents, anticancer agents, antipsychotics, antiretroviral agents, antiviral agents, benzodiazepines, calcium channel blockers, carbamazepine, cardiac glycosides, chlorzoxazone, cholesterol-lowering agents, clozapine, contraceptives, corticosteroids, cyclosporine, dextromethorphan, digoxin, drugs that may lower seizure threshold, estrogens, fertility agents, fexofenadine, heart rate-regulating agents, hepatotoxins, HMG-CoA reductase inhibitors, hormonal agents, loperamide (Imodium®), methylphenidate, monoamine oxidase inhibitors (MAOIs), mood stabilizers, morphine, non-nucleoside reverse transcriptase inhibitors (NNRTIs), omeprazole, opiates, pain relievers, PDE5 selective inhibitors, P-glycoprotein-regulated drugs, photosensitizing agents, protease inhibitors, sedatives, selective serotonin reuptake inhibitors (SSRIs), smoking cessation agents, testosterone, theophylline, thyroid hormones, tricyclic antidepressants (TCAs), Viagra®, weight loss agents, wound healing agents, zolpidem.

Interactions with Herbs and Dietary Supplements

St. John's wort may interfere with the way the body processes herbs and supplements using the liver's "cytochrome P450" enzyme system. As a result, the levels of these herbs and supplements may be increased in the blood (causing increased effects or potentially serious adverse reactions) or decreased in the blood (which may reduce the intended effects).

St. John's wort may alter the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto.

St. John's wort may alter blood sugar levels. Caution is advised when using herbs or supplements that may also alter blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.

St. John's wort may affect blood pressure. Caution is advised in people taking herbs and supplements that affect blood pressure.

St. John's wort may also interact with alcohol, anesthetics, anti-anxiety herbs and supplements, antibacterials, antidepressant herbs and supplements, antifungals, antihistamines, anti-inflammatory herbs and supplements, anticancer herbs and supplements, antioxidants, antipsychotics, antiviral herbs and supplements, cardiac glycosides, chasteberry, cholesterol-lowering herbs and supplements, contraceptives, fertility herbs and supplements, heart rate-regulating herbs and supplements, herbs and supplements for the eyes, herbs and supplements for the skin, herbs and supplements for the stomach and intestines, herbs and supplements that affect the nervous system, herbs and supplements that affect the immune system, herbs and supplements that damage the liver, herbs and supplements that lower seizure threshold, hormonal herbs and supplements, iron, melatonin, monoamine oxidase inhibitors (MAOIs), mood stabilizers, neurologic herbs and supplements, pain relievers, P-glycoprotein-regulated herbs and supplements, photosensitizing herbs and supplements, phytoestrogens, sedatives, selective serotonin reuptake inhibitors (SSRIs), smoking cessation herbs and supplements, thyroid hormones, tricyclic antidepressants (TCAs), valerian, weight loss herbs and supplements, wound healing herbs and supplements.

This evidence-based monograph was prepared by The Natural Standard Research Collaboration

www.naturalstandard.com