Herbal or dietary supplement	Drug	Comment	Recommendation*
Patients taking oral anticoagulants
Cranberry (juice)	Warfarin (Coumadin)	Interaction possible based on seven reports of increased INR, although a clinical study showed no interactions4–7	Suspect an interaction if INR elevated
Fish oil	Warfarin	Interaction possible, with case reports showing an elevated INR, although a clinical study showed no effect of fish oil on anticoagulation status8,9	Suspect an interaction if INR elevated
Garlic	Warfarin	Interaction unlikely based on a clinical study that found garlic is relatively safe and poses no serious hemorrhagic risk for closely monitored patients taking warfarin oral anticoagulation therapy10	Suspect an interaction if bruising or bleeding occurs despite an appropriate INR
		One review found no case reports of interactions with garlic and warfarin11
Ginkgo	Warfarin	Interaction possible, though controlled clinical studies show no effect of ginkgo on the kinetics or dynamics of warfarin12,13	Experts recommend caution, although available research does not support this conclusion
	Aspirin	Interaction suspected based on four case reports of spontaneous bleeding14,15	Suspect an interaction if spontaneous bleeding occurs
Ginseng	Warfarin	Interaction possible based on conflicting research findings	Avoid combination if possible
		American ginseng (Panax quinquefolius) reduces blood concentrations of warfarin16,17
		Coadministration of warfarin with Asian ginseng (Panax ginseng) did not affect the pharmacokinetics or pharmacodynamics of warfarin18
St. John's wort	Warfarin	Interaction suspected based on decreases in INR in case reports and in a study in 12 healthy volunteers18	Evaluate warfarin response when St. John's wort is initiated or stopped
Vitamin E (> 400 IU daily)	Warfarin	Interaction suspected based on a single patient (with rechallenge), resulting in an increase in INR19	Evaluate warfarin response when vitamin E is used in combination
		One clinical trial showed no interaction20
Patients taking cardiovascular medications
Eleuthero (Eleutherococcus senticosus) [ corrected]	Digoxin	Possible increase in digoxin levels without clinical signs (case report)21	Monitor digoxin level when eleuthero is initiated or stopped [ corrected]
St. John's wort	Digoxin	Suspected decrease in digoxin levels without clinical signs in a controlled study22	Monitor digoxin level when St. John's wort is initiated or stopped
	Verapamil (Calan)	Interaction suspected based on decreased bioavailability in a study in eight healthy volunteers23	Increase verapamil dose, if necessary, if diminished response occurs
	Statins	Interaction suspected based on decreased plasma blood levels in a clinical study24	Monitor serum lipid levels after St. John's wort is added
Patients taking psychiatric medications
Ginkgo	Atypical antidepressant (trazodone [Desyrel])	Interaction possible based on one case report of coma25	Evaluate for emotional and/or behavioral changes in patient response after ginkgo is initiated or stopped
Ginseng	Monoamine oxidase inhibitors	Interaction possible based on two case reports of manic-like symptoms, headache, and tremulousness17	Avoid combination if possible
St. John's wort	SSRIs	Interaction suspected based on case reports of drowsiness or serotonin syndrome26	Taper off St. John's wort when initiating an SSRI
	Benzodiazepines	Interaction suspected based on pharmacokinetic studies showing decreased serum levels (25 to 50 percent) without clinical signs27–29	Adjust the dose of benzodiazepine as needed
	Tricyclic antidepressants	Interaction possible based on decreased amitriptyline plasma levels but no clinical effects in a study of 12 depressed patients27,30	Monitor patient response after St. John's wort is initiated or stopped