What happens when you take tacrolimus with st. john's wort?
Tacrolimus is a calcineurin inhibitor used after kidney, liver, heart, and other organ transplants to prevent rejection, and at lower doses for some autoimmune and skin conditions. It is broken down by the CYP3A4 enzyme in the gut and liver and pumped out of cells by P-glycoprotein. Its therapeutic window is narrow, so relatively small shifts in how fast it is cleared can move blood levels into a range that is either too low to protect the graft or high enough to cause harm.
St. John's wort contains hyperforin, which activates a receptor in the gut and liver that increases the amount of CYP3A4 enzyme and P-glycoprotein the body makes. Here is the sequence:
- You start taking St. John's wort. Over the following weeks, the herb prompts your body to produce more of the enzyme and transporter that clear tacrolimus.
- Tacrolimus is now removed faster than before. Blood levels drift downward, and the drug's ability to suppress the immune system weakens.
- With levels too low, the transplanted organ becomes vulnerable to rejection. A clinician who does not know the herb is involved may raise the tacrolimus dose to bring levels back up.
- If the herb is later stopped, enzyme and transporter levels return to baseline over a couple of weeks. If the dose was raised in the meantime, tacrolimus levels can climb again and overshoot.
A published renal-transplant case (Bolley and colleagues) described kidney toxicity that became apparent when the CYP3A4 induction from St. John's wort wore off and tacrolimus concentrations rebounded above the intended range. A separate study in renal transplant patients (Mai and colleagues) measured a meaningful fall in tacrolimus blood exposure during St. John's wort treatment, requiring dose increases to maintain target levels.
Why is this important?
Tacrolimus exposure is one of the biggest determinants of both rejection risk and toxicity in transplant patients, and St. John's wort destabilizes that exposure in both directions.
When levels run too low, acute rejection can damage the transplanted organ and may require pulse steroids and intensified immunosuppression to bring under control. When levels run too high, tacrolimus can cause kidney damage, neurological effects such as tremor, headache, and confusion, new-onset diabetes after transplant, and high blood pressure.
The hardest part is the timing. The changes happen gradually over a week or two rather than immediately, so they can fall between routine clinic visits and be missed until a problem appears. Switching to a prolonged-release tacrolimus formulation does not solve this; extended-release products are still affected by the interaction.
What should you do?
Treat St. John's wort as off-limits while you are on tacrolimus, and let your transplant team manage any transition rather than acting on your own.
- Before any change (starting tacrolimus or considering a supplement): If you have been taking St. John's wort, tell your transplant team before your first tacrolimus dose so they can plan closer monitoring. Run any mood, sleep, anxiety, or menopause supplement past your doctor or pharmacist first, since the herb is often hidden in multi-ingredient blends.
- Every day while on tacrolimus: Avoid St. John's wort in all forms, take your tacrolimus exactly as prescribed, and keep a current list of every supplement you use to show at clinic visits.
- After a change (if you discover you have been combining them, or you stop the herb): Do not stop the herb or adjust your tacrolimus dose on your own. Contact your prescriber promptly. The team will typically arrange extra trough checks through the transition and adjust your dose to match your changing enzyme activity.
If you are dealing with low mood, several conventional antidepressants can be used with tacrolimus when chosen and monitored carefully. Some of them mildly affect CYP3A4 and may call for a modest tacrolimus dose adjustment, but they do not produce the two-way swings that St. John's wort causes. Ask your transplant team or a psychiatrist about options rather than self-treating.
Which specific products are affected?
On the medication side, the interaction applies to all systemic tacrolimus products, including immediate-release capsules (such as Prograf), extended-release products (such as Astagraf XL and Envarsus XR), and their generic equivalents. Topical tacrolimus ointment (Protopic) has minimal absorption into the bloodstream and is not the route of concern; if you also take oral tacrolimus, that is what matters here.
On the herb side, all Hypericum perforatum (St. John's wort) extracts can induce CYP3A4 to some degree, so there is no safe brand or formulation to pair with tacrolimus. Watch for it in capsules, tablets, tinctures, and teas, and read the full ingredient list on multi-ingredient mood and sleep blends, where St. John's wort is often combined with passionflower, valerian, kava, or 5-HTP without being featured on the front of the label. Topical St. John's wort salves and skin patches with red-oil extracts are generally low-exposure but worth flagging to your team. Very high homeopathic dilutions contain essentially no active compound and are unlikely to interact.
The science behind it
The mechanism (hyperforin activating the pregnane X receptor, which increases CYP3A4 and P-glycoprotein) is well established, and two human reports anchor this specific pairing:
- Mai I, et al. Nephrol Dial Transplant. 2003. A prospective pharmacokinetic study in renal transplant patients found that St. John's wort treatment substantially reduced tacrolimus blood exposure, requiring dose increases to keep levels in target range. PMID: 12637655.
- Bolley R, et al. Transplantation. 2002. A case report of a renal transplant recipient in whom tacrolimus-associated kidney toxicity became apparent as the CYP3A4 induction from St. John's wort resolved and drug concentrations rebounded. PMID: 11923712.
Major drug-interaction references, including Drugs.com, classify the St. John's wort and tacrolimus combination as a major interaction to be avoided.
Frequently Asked Questions
Can I take St. John's wort if my tacrolimus levels are checked regularly?
Regular monitoring helps but does not make the combination safe. The herb's effect builds and fades over a week or two, so levels can drift out of range between checks, and the situation is harder to manage when an over-the-counter herb is the moving part. The safer path is to avoid St. John's wort entirely.
What if I have already been taking both for a while?
Do not stop the herb or change your tacrolimus dose on your own. Contact your transplant team promptly so they can monitor your levels closely through the transition, because tacrolimus can rebound upward once the herb is out of your system.
Does switching to extended-release tacrolimus avoid the problem?
No. Extended-release tacrolimus is still affected by St. John's wort. Changing the formulation does not protect you from the interaction.
Is topical St. John's wort a problem?
Salves and skin patches generally deliver far less than oral products, so systemic effects are unlikely, but it is still worth mentioning anything you use to your transplant team.
I take tacrolimus ointment for eczema, not pills. Does this apply to me?
Topical tacrolimus ointment is barely absorbed into the bloodstream, so this interaction is about oral or systemic tacrolimus. If you only use the ointment and take no oral tacrolimus, this specific concern does not apply, though it is always worth confirming with your prescriber.
I am taking St. John's wort for low mood. What can I use instead?
Several conventional antidepressants can be used alongside tacrolimus when chosen and monitored carefully. Ask your transplant team or a psychiatrist to help you pick one rather than self-treating with the herb.
Key takeaways
- St. John's wort and tacrolimus should not be combined; this is treated as a contraindication.
- The herb speeds up tacrolimus clearance, lowering blood levels and raising the risk of transplant rejection.
- Stopping the herb can let tacrolimus levels rebound, which has been linked to kidney toxicity.
- The effect builds and fades over a week or two, so it can be missed between routine clinic visits.
- Extended-release tacrolimus is not protected from the interaction.
- If you have been combining them, do not adjust anything yourself; contact your transplant team promptly.