Medication Interactions with Oil of Oregano and Black Seed Oil
Yes, both oil of oregano and black seed oil have clinically significant interactions with anticoagulants, diabetes medications, and potentially other drug classes that require careful monitoring and possible discontinuation before elective procedures.
Oil of Oregano Interactions
Anticoagulant Interactions (Warfarin)
Oil of oregano significantly increases INR values in patients taking warfarin, creating a serious bleeding risk. A documented case showed INR rising from therapeutic range (2-3) to 6.42 after one week of oregano tea consumption (200 mL daily), which normalized only after discontinuation 1.
The mechanism is dual: oregano contains high concentrations of carvacrol and thymol that exhibit direct anticoagulant activity, while its polyphenols, tannins, and flavonoids inhibit CYP2C9 and CYP3A4 enzymes responsible for metabolizing acenocoumarol and warfarin 1.
For patients on warfarin taking oregano oil, discontinue the supplement immediately and monitor INR closely. If the patient insists on continuing, use highly diluted preparations, reduce warfarin dose (as demonstrated by the case requiring dose reduction to 1/4 tablet), and increase INR monitoring frequency 1.
Perioperative Bleeding Risk
The Society for Perioperative Assessment and Quality Improvement (SPAQI) does not specifically list oregano oil, but given its documented anticoagulant properties and CYP450 inhibition, oregano oil should be discontinued at least 2 weeks before any elective surgery following the same precautions as other antiplatelet herbs 2.
Oregano's antiplatelet effects combined with sevoflurane or other platelet-inhibiting drugs used perioperatively increases bleeding risk 2.
Diabetes Medication Interactions
- While not specifically documented for oregano oil in the provided evidence, herbs that affect CYP2C9 metabolism (which oregano does) can theoretically alter the metabolism of sulfonylureas like glyburide 1.
Black Seed Oil Interactions
Serotonin Syndrome Risk
Black seed oil can precipitate serotonin syndrome in patients taking serotonergic medications (SSRIs, SNRIs, tramadol, ondansetron). A case report documented immediate postoperative serotonin syndrome in a patient using black seed oil supplements 3.
Discontinue black seed oil at least 2 weeks before elective procedures, particularly in patients on any serotonergic medications including common perioperative drugs like ondansetron 3.
Diabetes Medication Interactions
Black seed oil improves insulin resistance and increases insulin sensitivity, creating hypoglycemia risk when combined with metformin, sulfonylureas, or insulin 2.
For patients on diabetes medications taking black seed oil, increase glucose monitoring frequency and be prepared to reduce diabetes medication doses to prevent hypoglycemia 2.
Antihypertensive Interactions
Black seed oil contains andrographolide and other diterpenes that lower blood pressure, potentially causing additive hypotensive effects with ACE inhibitors like lisinopril 2.
Monitor blood pressure more frequently when black seed oil is initiated or discontinued in patients on antihypertensives 2.
General Recommendations for Both Supplements
Preoperative Management
The American Society of Anesthesiology recommends discontinuing all dietary supplements 1-2 weeks before surgery due to unpredictable pharmacokinetics and inconsistent manufacturing 2.
In a surgical population study, 16.5% of patients taking supplements had potential drug interactions with sedation, and 19% had coagulation interactions, with 12.5% of the latter group experiencing actual intraoperative hemorrhage 2.
Monitoring Strategy
Document all herbal supplement use at every clinical encounter, as commercially available products lack standardization and vary widely in active ingredient content 2, 4.
When patients on anticoagulants use these supplements, monitor INR within 3-7 days of starting or stopping the supplement, as interactions can manifest within days to weeks 1, 5.
Clinical Pitfalls to Avoid
Do not assume herbal products are safe simply because they are "natural" - both oregano oil and black seed oil have documented serious drug interactions 1, 3.
Patients often fail to disclose supplement use unless specifically asked; use open-ended questions about "vitamins, herbs, teas, or natural products" rather than just asking about "medications" 2.
The interaction risk increases with higher doses and longer duration of supplement use 1.
For anticoagulated patients who insist on using oregano, the only safe approach is dramatically increased INR monitoring (every 3-4 days initially) with preemptive warfarin dose reductions of 25-50% 1, 4.