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St. John's Wort Interactions: Medicines to Know
St. John's wort interactions are common and can be serious. The herb can weaken many medicines, including antidepressants, birth control pills, warfarin, some seizure, heart, HIV and cancer drugs, and transplant drugs. If you take any prescription, ask your doctor or pharmacist before using a product that names it.
By the MemoPryl label deskUpdated · 4 min read
What are St. John's wort interactions?
St. John's wort interactions are changes in how a medicine works when the herb is taken at the same time. In most cases the herb makes the medicine weaker.
NCCIH puts it plainly: the herb can weaken the effects of many medicines, "including crucially important medicines" (NCCIH, St. John's Wort safety).
MemoPryl matters here because St. John's wort is one of six names tied to a sibling MemoPryl pack. It is not confirmed for the bottle you receive, and no amount is printed on any image we have. Check your bottle.
Which medicines does St. John's wort affect?
It affects antidepressants, birth control pills, warfarin, cyclosporine, some seizure drugs, some heart medicines, some HIV and cancer drugs, and certain statins (NCCIH, St. John's Wort safety).
Other public sources add more names. NCCIH also lists digoxin and oxycodone (NCCIH, St. John's Wort in depth). Memorial Sloan Kettering adds tacrolimus and some chemotherapy drugs (MSK, St. John's Wort). FDA lists depression, heart disease, HIV and transplant medicines (FDA, Mixing Meds and Supplements).
The table is a short guide, not a full list. Natural does not always mean safe, and NCCIH uses this herb as its example (NCCIH, Using Supplements Wisely).
| Medicine group | Named examples | Source |
|---|---|---|
| Antidepressants | Amitriptyline, bupropion | NCCIH |
| Birth control | Birth control pills | NCCIH, MSK, FDA |
| Blood thinners | Warfarin | NCCIH, MSK |
| Transplant drugs | Cyclosporine, tacrolimus | NCCIH, MSK |
| Heart medicines | Digoxin, some others | NCCIH, MSK, FDA |
| HIV and cancer drugs | Some of each | NCCIH, FDA |
| Seizure drugs and statins | Some of each | NCCIH |
Why does St. John's wort weaken other medicines?
Our sources say that it does, but the pages we rely on do not explain the full mechanism, so we will not guess at one.
What matters for you is the result. A medicine that works well alone may work less well with the herb. That can matter most for drugs where a steady level protects you, such as transplant, heart and blood thinning medicines.
There is a second type of problem. With certain antidepressants and other drugs that affect serotonin, the herb can lead to serious serotonin-related side effects (NCCIH, St. John's Wort safety). NCCIH calls the rise in serotonin potentially life-threatening (NCCIH, St. John's Wort in depth).
MemoPryl: capsules in 2, 3 or 6 bottlesRead the bottle · check medicines first · 60-day window (confirm)
See packsDoes the MemoPryl label warn about St. John's wort?
No warning text is printed on any bottle image we have. The front shows a name, three claims, a capsule count and the words "Dietary Supplement".
Tap the numbered spots to see what the bottle front shows.
Tap a number to see what that part of the label says.
- Heading
'COGNITIVE SUPPORT FORMULA*'. The asterisk refers to the FDA statement, which this image does not show.
- Name
MemoPryl, with a TM mark, in a panel edged in gold. This version prints no maker line.
- Network art
A faint sketch of nodes and links. It is decoration, not an ingredient list.
- Claims
'Supports Focus*', 'Optimized Memory*' and 'Improves Mental Clarity*', and each one carries the FDA asterisk.
- Product type
'DIETARY SUPPLEMENT'. It is not a drug.
- Count
'30 Capsules'. The other bottle image says 60.
A label with no warnings is a reason to ask the seller and your pharmacist before the first capsule.
What should I ask before taking a product with St. John's wort?
Ask your doctor or pharmacist before you start, and bring the bottle. Keep taking your prescribed medicine exactly as directed while you ask.
FDA says a health professional may ask you to stop supplements two to three weeks before a procedure (FDA, Mixing Meds and Supplements). MSK suggests stopping St. John's wort at least one week before surgery or chemotherapy (MSK, St. John's Wort).
It may also be unsafe in pregnancy (NCCIH, St. John's Wort safety).
Thinking about MemoPryl?Check your medicines with a pharmacist first. The checkout confirms prices and the 60-day window.
Middle pack
3 bottles
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Get 3 bottlesLargest pack
6 bottles
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Get 6 bottlesUntil the seller confirms its list, prices stay as fill-in fields. The checkout shows the final total.
For the wider picture see the MemoPryl medicine guide, the St. John's wort page and the side effects page.
FAQ01
Questions people ask about MemoPryl
Is St. John's wort safe if I take no prescriptions?
It may be safer, but not risk free. MSK lists headache, nausea, dry mouth, sleepiness, stomach upset and more sun sensitivity as common effects. Large oral doses may also cause severe skin reactions after sun exposure.
How far ahead of surgery do I stop St. John's wort?
MSK says to stop it at least one week before surgery or chemotherapy. FDA adds that a clinician may ask you to stop supplements two to three weeks before a procedure. Follow your surgical team.
Can a pharmacist check my medicines against a supplement?
Yes. Pharmacists are trained to check drug and supplement combinations. Bring the bottle or a photo of its label, plus your medicine list.
Who wrote this02
Written and reviewed by
Each page draws on the bottle images, the seller's product notes and linked NIH, FDA, FTC and peer-reviewed sources.
Last updated . See our editorial standards and how we check reviews. This website is run by MemoPryl USA retail, not by the manufacturer or the distributor of the bottle. We are paid a commission when you buy through our order links.
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Read the bottle you receive and go over your medicines with a pharmacist before you pick a pack. The checkout confirms prices and the guarantee terms.
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