Risky drug and supplement combinations are getting more press. There are thousands of POTENTIAL interactions. Many don't cause noticeable problems, so they tend to fall off the radar. But watch for the few that are more likely to be significant when taking medication histories.
St. John's wort induces CYP450 enzymes and P-glycoprotein and can DECREASE the efficacy of apixaban, rivaroxaban, digoxin, cyclosporine and possibly others. Clopidogrel's antiplatelet activity can be INCREASED with St. John's wort. Be alert for bleeding if these are combined. St. John's wort might also lead to serotonin syndrome with SSRIs, etc. Think of this if a patient reports jitteriness, muscle spasms, etc.
Glucosamine alone or with chondroitin might increase bleeding risk with warfarin. Consider this as a possible cause for INR changes especially if it's within several weeks of using them together.
Ginkgo is linked to seizures in patients stable on epilepsy medications and might increase bleeding with antithrombotics (aspirin, apixaban, etc). To be safe, advise avoiding ginkgo with these medications.
REFERENCES
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Knudsen JF, Sokol GH. Potential glucosamine-warfarin interaction resulting in increased international normalized ratio: case report and review of the literature and MedWatch database. Pharmacotherapy. 2008 Apr;28(4):540-8. Available at: https://pubmed.ncbi.nlm.nih.gov/18363538
Wang ZY, Chen M, Zhu LL, Yu LS, Zeng S, Xiang MX, Zhou Q. Pharmacokinetic drug interactions with clopidogrel: updated review and risk management in combination therapy. Ther Clin Risk Manag. 2015 Mar 19;11:449-67. Available at: https://www.dovepress.com/pharmacokinetic-drug-interactions-with-clopidogrel-updated-review-and--peer-reviewed-fulltext-article-TCRM
Qato DM, Wilder J, Schumm LP, Gillet V, Alexander GC. Changes in Prescription and Over-the-Counter Medication and Dietary Supplement Use Among Older Adults in the United States, 2005 vs 2011. JAMA Intern Med. 2016 Apr;176(4):473-82. Available at: https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2500064