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Am Fam Physician. 2008 Jan 1;77(1):73-8.

Herbal and dietary supplement--drug interactions in patients with chronic illnesses.

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Osher Institute, Division for Research and Education in Complementary and Integrative Medical Therapies, USA.

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  • Am Fam Physician. 2008 Oct 1;78(7):808.


Herbs, vitamins, and other dietary supplements may augment or antagonize the actions of prescription and nonprescription drugs. St. John's wort is the supplement that has the most documented interactions with drugs. As with many drug-drug interactions, the information for many dietary supplements is deficient and sometimes supported only by case reports. Deleterious effects are most pronounced with anticoagulants, cardiovascular medications, oral hypoglycemics, and antiretrovirals. Case reports have shown a reduction in International Normalized Ratio in patients taking St. John's wort and warfarin. Other studies have shown reduced levels of verapamil, statins, digoxin, and antiretrovirals in patients taking St. John's wort. Physicians should routinely ask patients about their use of dietary supplements when starting or stopping a prescription drug, or if unexpected reactions occur.

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