Possible Interaction: Warfarin and St John's Wort

“In addition, cranberry, danshen, dong quai, Ginkgo, ginseng, green tea, and St John's wort were found to have potential interactions with warfarin.”

“The case reports with severe adverse effects such as spontaneous postoperative …, thrombosis, subarachnoid hemorrhage and/or subdural hematomas after concomitant use of warfarin and …, Hypericum perforatum , Salvia milthiorizza, Gingko biloba, Serenoa repens, Angelica sinensis, Vaccinium species, Allium sativum, … barbarum, Matricaria chamomilla, Boswellia serrata and Camellia sinensis have been estimated.”

“Psychotropics that may significantly decrease the INR when used with warfarin include trazodone, St. John's wort , carbamazepine, and the polycyclic aromatic carbons in tobacco cigarettes; however, nicotine itself, as in nicotine replacement strategies, is not known to alter warfarin's anticoagulant effect.”

“Lastly, multiple herb-drug interactions have been identified with St. John's wort that involve significantly reduced AUC and blood concentrations of warfarin , digoxin, indinavir, theophylline, cyclosporine, tacrolimus, amitriptyline, midazolam, and phenprocoumon.”

“Results from clinical studies and case reports indicate that self-administered SJW reduce steady state plasma concentrations of amitriptyline, cyclosporine, digoxin, fexofenadine, amprenavir, indonavir, lopinavir, ritonavir, saquinavir, benzodiazepines, theophyline, irinotecan, midazolan and warfarin.”

“Since then, subsequent research has shown that SJW altered the pharmacokinetics of drugs such as digoxin, tacrolimus, indinavir, warfarin , alprazolam, simvastatin, or oral contraceptives.”

“The herbs that showed the greatest potential to interact with warfarin include garlic, ginger, ginkgo, St. John's wort , and ginseng, i.e. plants normally consumed as food and also used for therapeutic purposes.”

“For example, St John's wort significantly reduced the area under the plasma concentration-time curve (AUC) and blood concentrations of cyclosporine, midazolam, tacrolimus, amitriptyline, digoxin, indinavir, warfarin , phenprocoumon and theophylline.”

“Case reports or case series suggest interactions of St John’s wort with adrenergic vasopressors, anaesthetics, bupropion, buspirone, ciclosporin, eletriptan, loperamide, nefazodone, nevirapine, oral contraceptives, paroxetine, phenprocoumon, prednisone, sertraline, tacrolimus, theophylline, tibolone, tryptophan, venlafaxine and warfarin.”

“Clinical trials … wort Hypericum perforatum ), via cytochrome P450 (CYP) and/or P-glycoprotein induction, reduces the plasma concentrations (and/or increases the clearance) of alprazolam, amitriptyline, atorvastatin, …, erythromycin, fexofenadine, gliclazide, imatinib, indinavir, irinotecan, ivabradine, mephenytoin, methadone, midazolam, nifedipine, omeprazole, oral contraceptives, quazepam, simvastatin, tacrolimus, talinolol, verapamil, voriconazole and warfarin.”

“The action of warfarin is reduced by St Johns Wort [9].”