Can I Take St. John's Wort with Repatha (Evolocumab)?

Why This Question Is More Nuanced Than It Looks

Most drug-supplement interaction questions resolve simply: the supplement induces or inhibits a cytochrome P450 enzyme, and the drug is either a substrate of that enzyme or it is not. St. John's Wort is one of the most potent botanical inducers of CYP3A4 and P-glycoprotein described in the clinical literature, so the concern is reasonable.

Repatha breaks that familiar pattern. Evolocumab is a 144-kDa IgG2 monoclonal antibody administered subcutaneously. It is not absorbed orally, it does not enter the hepatocyte to be oxidized, and its clearance depends on proteolytic catabolism common to all endogenous immunoglobulins, not on any enzyme that St. John's Wort can induce or inhibit. The FDA label for evolocumab contains no drug interaction section mentioning CYP isoforms, precisely because none apply.

Three indirect risk categories remain relevant. They involve the other drugs in your regimen, potential effects on lipid metabolism itself, and St. John's Wort's documented capacity to worsen mood instability in people who rely on the herb as an antidepressant substitute while also managing high cardiovascular risk.

How St. John's Wort Interacts With the Body

CYP3A4 and P-Glycoprotein Induction

St. John's Wort contains at least two pharmacologically active constituent classes: naphthodianthrones (primarily hypericin) and phloroglucinols (primarily hyperforin). Hyperforin is the compound primarily responsible for pregnane X receptor (PXR) activation, the nuclear receptor pathway that transcriptionally upregulates CYP3A4, CYP2C9, and intestinal P-glycoprotein. A landmark pharmacokinetic study published in The Lancet documented a 49% reduction in plasma levels of the immunosuppressant cyclosporine in transplant patients who began taking St. John's Wort, leading to acute organ rejection in several cases.

The clinical consequence: any drug that is an oral CYP3A4 substrate taken simultaneously with St. John's Wort may reach subtherapeutic concentrations.

What CYP3A4 Induction Does NOT Do to Biologics

Monoclonal antibodies such as evolocumab, alirocumab, dupilumab, and adalimumab are not substrates of any cytochrome P450 isoform. Their catabolism occurs in lysosomes after receptor-mediated endocytosis or pinocytosis, generating amino acids that re-enter general protein pools. Research on biologic pharmacokinetics from the NIH confirms that CYP-based drug-drug interaction studies are not required for monoclonal antibodies under current FDA guidance, because the metabolic pathway simply does not involve those enzymes.

St. John's Wort cannot lower evolocumab plasma levels through enzyme induction. Period.

The Real Risk: Concurrent Statin and Antidepressant Therapy

This is where the conversation changes materially. Patients on Repatha are almost never on Repatha alone.

St. John's Wort Plus Statins

Most people prescribed evolocumab are also taking a high-intensity statin. The combination of evolocumab 140 mg every two weeks added to atorvastatin 40 mg or 80 mg is the most common clinical scenario in the FOURIER trial population, where 69% of participants were on high-intensity statins at baseline. FOURIER (N=27,564) demonstrated that adding evolocumab to statin therapy reduced LDL-C by a further 59% and cut major adverse cardiovascular events by 15% over a median 2.2 years.

St. John's Wort reduces atorvastatin AUC by approximately 35% and simvastatin AUC by up to 51%, based on crossover pharmacokinetic studies. A published PK study in the British Journal of Clinical Pharmacology quantified simvastatin and simvastatin acid reductions across 12 healthy subjects taking standardized St. John's Wort 300 mg three times daily. The authors found statistically significant AUC reductions of 51.8% for simvastatin and 62.3% for simvastatin acid (P<0.001 for both).

Simpler put: if you add St. John's Wort to a Repatha-plus-statin regimen, Repatha's 59% LDL-C reduction remains fully intact while your statin's contribution may be cut nearly in half. Your overall LDL-C target becomes harder to reach.

St. John's Wort Plus SSRIs or SNRIs

Patients managing both cardiovascular disease and depression represent a sizable clinical group. Approximately 20% of post-myocardial infarction patients meet criteria for major depressive disorder, according to data published in JAMA. When these patients are on an SSRI such as sertraline or escitalopram alongside Repatha, adding St. John's Wort creates serotonin syndrome risk. St. John's Wort inhibits synaptic reuptake of serotonin, dopamine, and norepinephrine, and its combination with an SSRI can produce additive serotonergic excess. The FDA issued a Public Health Advisory on serotonin syndrome risk from St. John's Wort-SSRI combinations in February 2000.

This risk does not involve evolocumab at all. But if you are a Repatha patient who is also depressed and self-medicating with St. John's Wort instead of or alongside a prescribed antidepressant, the combination is potentially dangerous.

Does St. John's Wort Directly Affect LDL or Cardiovascular Outcomes?

Animal and In Vitro Evidence

A small body of laboratory research suggests hyperforin may modestly activate bile acid synthesis pathways via FXR (farnesoid X receptor) partial agonism, which could theoretically affect cholesterol metabolism. Preclinical data in mice published in PubMed showed CYP7A1 upregulation with hyperforin exposure, a finding that suggests slightly accelerated cholesterol-to-bile-acid conversion. Whether this translates to clinically meaningful LDL-C changes in humans taking therapeutic doses of St. John's Wort has not been tested in a powered clinical trial.

The direction of any effect, if real in humans, is uncertain. CYP7A1 upregulation would increase bile acid synthesis and could lower LDL-C slightly via LDL receptor upregulation, the same downstream logic as bile acid sequestrants such as colesevelam.

No Human RCT Data

No randomized controlled trial has examined LDL-C, HDL-C, or triglyceride outcomes as primary endpoints in patients specifically randomized to St. John's Wort. The available evidence is mechanistic or observational. Anyone telling you St. John's Wort "lowers cholesterol" or "raises cholesterol" meaningfully is extrapolating far beyond the data.

Evolocumab Pharmacology: Why Biologics Are Different

Mechanism of Action

Evolocumab is a fully human IgG2 monoclonal antibody that binds PCSK9 (proprotein convertase subtilisin/kexin type 9) with high affinity (Kd approximately 0.3 nM). PCSK9 normally binds surface LDL receptors on hepatocytes and routes them to lysosomal degradation. By blocking this interaction, evolocumab allows LDL receptors to recycle to the hepatocyte surface, increasing LDL-C clearance. The FDA label summarizes the mechanism and clinical pharmacology in detail.

Absorption and Clearance

After subcutaneous injection, evolocumab reaches peak serum concentration in three to four days. Bioavailability is approximately 72%. Clearance occurs via two routes: a non-saturable proteolytic pathway (dominant at therapeutic concentrations) and a saturable target-mediated route through PCSK9 binding. Neither pathway involves cytochrome P450, UDP-glucuronosyltransferase, or P-glycoprotein. The mean half-life is roughly 11 to 17 days, depending on dose.

Immune Complex and Protein-Binding Considerations

St. John's Wort does not significantly alter plasma protein composition or immunoglobulin catabolism rates. There is no published mechanistic basis for St. John's Wort affecting evolocumab's pharmacokinetics through any known route of interaction.

Monitoring Recommendations If You Choose to Continue Both

If your prescriber reviews the situation and concludes the combination is acceptable in your specific case, apply this monitoring approach:

Lipid panel timing. Obtain a fasting lipid panel 8 to 12 weeks after starting, stopping, or changing the dose of St. John's Wort, because any statin-mediated effect on LDL-C will stabilize within that window. Your evolocumab-driven LDL-C reduction should remain stable; if LDL-C rises above your target (typically <70 mg/dL for established ASCVD per 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease), suspect statin underperformance before assuming evolocumab failure.

Statin level consideration. If you take simvastatin and insist on St. John's Wort, ask about switching to rosuvastatin. Rosuvastatin is primarily a CYP2C9 substrate rather than CYP3A4, and data from a pharmacokinetic study on CYP2C9 substrates and St. John's Wort suggest smaller AUC reductions compared with CYP3A4-dependent statins.

Mood and serotonin watch. If you take any serotonergic medication, tell your prescriber before adding St. John's Wort. Watch for agitation, diaphoresis, tremor, hyperthermia, or rapid heart rate, all early signs of serotonin excess that warrant immediate medical attention.

Injection site and immune function. No specific monitoring adjustment is needed for evolocumab itself. Its pharmacokinetics will not change.

What the Guidelines Say

The 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease states:

"Clinicians should inquire about the use of dietary supplements and herbal products, as some may interfere with prescribed cardiovascular medications." ACC/AHA 2019 Prevention Guideline, Section 5.4

The European Society of Cardiology 2019 dyslipidaemia guidelines similarly note that CYP3A4-inducing supplements reduce statin efficacy and should be avoided in patients on intensive lipid-lowering therapy. The ESC document does not specifically address PCSK9 inhibitors and St. John's Wort because no pharmacokinetic interaction exists, but the statin-specific guidance is directly applicable to combination regimens.

The Natural Medicines Comprehensive Database rates the St. John's Wort-statin interaction as "Major" and the St. John's Wort-evolocumab combination as having "Insufficient Reliable Evidence" for a direct interaction, which aligns with the mechanistic analysis above.

Special Populations

Familial Hypercholesterolemia

Patients with heterozygous familial hypercholesterolemia (HeFH) have a particularly narrow margin for LDL-C control. In the TESLA Part B trial (N=49), evolocumab 420 mg monthly reduced LDL-C by 30.9% even in homozygous FH patients with severely impaired LDL receptor function. TESLA Part B results are indexed in PubMed. For this population, any supplement that degrades statin efficacy is especially consequential because statin-plus-evolocumab is often the only non-apheresis combination available.

Post-MI Depression Comorbidity

As noted earlier, roughly 1 in 5 post-MI patients develops major depressive disorder. This group is heavily represented among Repatha users given that established ASCVD is a primary indication. Self-treating depression with St. John's Wort instead of engaging a prescriber is a pattern that creates real hazard: uncontrolled depression, potential serotonin syndrome from SSRI overlap, and possible statin underperformance if simvastatin or atorvastatin is in the regimen.

Elderly Patients on Polypharmacy

Older adults on Repatha frequently take additional CYP3A4-dependent drugs: amlodipine, diltiazem, certain anticoagulants, or immunosuppressants after organ transplant. St. John's Wort interacts with every one of these. The evolocumab component of the regimen will be unaffected, but the rest of the cardiovascular medication stack may be compromised.

Practical Advice Before Stopping or Starting St. John's Wort

1. Do not stop St. John's Wort abruptly if you have been taking it for more than four weeks for mood support. Discontinuation should be gradual and ideally supervised.
2. Tell your prescriber and pharmacist about every supplement you take at every visit. The phrase "it's just a supplement" has preceded serious drug interactions in published case reports.
3. If depression is the reason you are considering St. John's Wort, ask your prescriber about evidence-based options. Sertraline and escitalopram have cardiovascular safety data in post-MI populations. SADHART-CHF (N=469) found sertraline safe in heart failure patients with depression, though it did not demonstrate a mortality benefit.
4. If you are already taking both evolocumab and St. John's Wort, your evolocumab efficacy is almost certainly intact. Request a fasting LDL-C panel to confirm your statin is still performing, then work with your prescriber on a plan.