What happens when you take omeprazole with st. john's wort?
St. John's wort (Hypericum perforatum) is one of the most potent natural enzyme inducers known. When it speeds up the liver enzymes that clear omeprazole, less of the drug stays in your bloodstream and its acid-suppressing effect can fade. Here is the sequence:
- Hyperforin activates a master switch. Hyperforin, an active constituent of St. John's wort, switches on the pregnane X receptor (PXR), a regulator that tells the liver and gut to make more drug-metabolizing machinery.
- The body ramps up clearance enzymes. Over about two weeks of regular use, this raises the activity of cytochrome P450 enzymes CYP3A4 and CYP2C19, plus the drug efflux transporter P-glycoprotein.
- Omeprazole is broken down through two routes at once. Omeprazole is cleared mainly by CYP2C19 and secondarily by CYP3A4. St. John's wort induces both pathways simultaneously, so the drug is removed faster than normal.
- Blood levels and acid suppression drop. With clearance ramped up, omeprazole plasma concentrations fall and proton-pump inhibition weakens, which can let stomach acid creep back up.
Why is this important?
Omeprazole is prescribed for conditions where losing acid suppression has real consequences, and St. John's wort's effects extend far beyond this one drug.
For peptic ulcers and severe reflux, weaker acid suppression can mean breakthrough symptoms return, esophagitis may not heal, and ulcers carry a risk of bleeding. For H. pylori eradication, triple- and quadruple-therapy regimens depend on the proton-pump inhibitor to keep stomach pH high enough for the antibiotics to work — reduced omeprazole exposure can drop eradication rates and make resistant H. pylori more likely.
The broader issue is that St. John's wort induces enzymes and transporters that handle a large share of marketed medicines. Other clinically important combinations include warfarin (reduced blood thinning, clot risk), oral contraceptives (contraceptive failure and unintended pregnancy), immunosuppressants such as cyclosporine and tacrolimus (transplant rejection), certain antiretrovirals (loss of HIV control), and antidepressants like SSRIs (added serotonergic effect). Regulators have placed specific warnings on multiple drug labels because of St. John's wort interactions.
What should you do?
The safest move is to keep these two apart and let your clinician guide any changes. Here is how to handle each stage.
Before changing anything:
- Tell your doctor and pharmacist every supplement you take, including St. John's wort. Many people use it for low mood, anxiety, or sleep and do not think of it as a real medicine, so it often goes unmentioned.
- If you take omeprazole as part of an H. pylori eradication course, do not add St. John's wort during treatment — eradication is high-stakes and failure breeds resistance.
Every day, if you currently take both:
- Watch for the return of reflux, heartburn, or ulcer symptoms, which can signal that your omeprazole is no longer working as well.
- Do not stop omeprazole abruptly on your own — rebound acid hypersecretion can occur. Keep taking it as prescribed while you sort out a plan.
After a change (stopping St. John's wort):
- Remember that enzyme induction does not switch off immediately. It takes roughly two weeks for enzyme activity to return to baseline, so omeprazole may stay less effective during that window.
- Ask your doctor or pharmacist whether your acid-suppression plan needs adjusting while the effect washes out.
- For mood concerns, ask your clinician about other evidence-based options and therapies that do not interfere with omeprazole the way St. John's wort does.
Which specific products are affected?
St. John's wort is sold as standardized Hypericum perforatum extract under many brand names. Examples include Kira, Nature's Way St. John's Wort, Nature's Bounty, Solgar, and NOW, along with generic Hypericum extracts and tea preparations. The interaction is driven mainly by hyperforin content, so high-hyperforin extracts induce enzymes more strongly than low-hyperforin ones — but standard preparations generally induce enough to matter.
On the omeprazole side, the interaction applies to all formulations, including Prilosec OTC, prescription Prilosec, omeprazole/sodium bicarbonate (Zegerid), and generic omeprazole capsules and tablets. It also extends to related proton-pump inhibitors that rely on the same enzymes: esomeprazole (Nexium), pantoprazole (Protonix), lansoprazole (Prevacid), and rabeprazole (AcipHex). Pantoprazole and rabeprazole depend less on CYP2C19, so the effect may be somewhat smaller, but it is still worth accounting for.
The science behind it
The most directly relevant evidence is a controlled human pharmacokinetic study by Wang and colleagues (2004), which gave healthy volunteers St. John's wort for two weeks and measured omeprazole afterward. It found that omeprazole exposure fell while the levels of its CYP3A4- and CYP2C19-derived metabolites rose — confirming that St. John's wort speeds omeprazole clearance through both enzyme pathways at once (PMID 15001970).
A mechanism review by Chrubasik-Hausmann and colleagues (2019) explains why the effect depends on hyperforin: hyperforin activates PXR, which drives the CYP3A4 and CYP2C19 induction behind these interactions, so higher-hyperforin products tend to cause stronger effects. Clinical reference monographs (Drugs.com) likewise flag that St. John's wort can lower omeprazole levels and efficacy through enzyme induction. Together these sources consistently support the direction and mechanism of this interaction.
Frequently Asked Questions
Does St. John's wort make omeprazole completely stop working?
Not completely, but it can meaningfully reduce how much omeprazole reaches your bloodstream, which weakens acid suppression. For serious conditions like ulcers or H. pylori treatment, even a partial loss of effect can matter.
Can I just take them a few hours apart?
No. This is not a timing problem you can space out. St. John's wort changes how your body makes drug-clearing enzymes over weeks, so the effect persists regardless of when in the day you take each one.
How long does the interaction last after I stop St. John's wort?
Enzyme activity returns toward normal over roughly two weeks after you stop, so omeprazole may remain less effective during that washout period. Ask your clinician whether any adjustment is needed in the meantime.
I take St. John's wort for my mood. What are my options?
Talk to your clinician. There are other evidence-based treatments for low mood — including therapy and structured behavioral approaches — that do not interfere with omeprazole the way St. John's wort does.
Is this interaction the same with other acid reducers?
It applies across the proton-pump inhibitor class that relies on CYP2C19 and CYP3A4 (esomeprazole, lansoprazole, and others). Pantoprazole and rabeprazole depend slightly less on CYP2C19, so the effect may be smaller, but it is still present.
Should I stop omeprazole if I have been taking both?
Do not stop omeprazole abruptly on your own, as rebound acid can occur. Stop the St. John's wort instead and review your plan with your doctor or pharmacist.
Key takeaways
- St. John's wort induces CYP3A4 and CYP2C19, the enzymes that clear omeprazole, lowering its blood levels and weakening acid suppression.
- This can undermine treatment of GERD, peptic ulcers, and especially H. pylori eradication — so the combination is best avoided.
- The effect builds and fades over about two weeks, so it is not fixed by spacing the doses apart.
- Do not stop omeprazole abruptly; stop St. John's wort and review your medication and supplement list with your doctor or pharmacist.
- St. John's wort also interacts with many other drugs, including warfarin, oral contraceptives, and immunosuppressants — always disclose it to your prescriber.