Can I Take St. John's Wort with Leqvio (Inclisiran)?

How Inclisiran Works and Why the Metabolic Route Matters

Inclisiran (Leqvio) is a small interfering RNA (siRNA) that silences hepatic PCSK9 messenger RNA, reducing LDL receptor degradation and lowering circulating LDL-C. The FDA approved inclisiran in December 2021 for adults with heterozygous familial hypercholesterolemia or established atherosclerotic cardiovascular disease who need additional LDL lowering on top of maximally tolerated statin therapy. [1]

Inclisiran's Metabolic Pathway Is Unusual

Unlike statins or most oral medications, inclisiran is not metabolized by cytochrome P450 enzymes. After subcutaneous injection, it is taken up rapidly by hepatocytes via the GalNAc ligand system and undergoes nucleolytic degradation within the cell. [2] Because CYP3A4, CYP2C9, and similar drug-metabolizing enzymes are not involved in inclisiran's clearance, inducers of those enzymes, including St. John's Wort, cannot meaningfully accelerate inclisiran breakdown through the classical pharmacokinetic pathway.

The FDA prescribing information for Leqvio lists no CYP-based drug interactions. [1] Renal excretion of small nucleotide fragments accounts for the minor systemic clearance that does occur.

ORION Trial Evidence on Efficacy

In ORION-11 (N=1,617), inclisiran 300 mg (inclisiran sodium 352 mg equivalent) given at baseline, 3 months, then every 6 months produced a time-averaged LDL-C reduction of 50.5% versus placebo at day 510 (P<0.001). [3] In ORION-10 (N=1,561), time-averaged LDL-C reduction was 52.3% versus placebo over the same period. [4] These reductions were consistent regardless of background statin use.

What St. John's Wort Does Pharmacologically

St. John's Wort (Hypericum perforatum) is one of the most thoroughly studied herbal CYP inducers in clinical pharmacology. Standardized extracts containing 0.3% hypericin and 3 to 5% hyperforin activate pregnane X receptor (PXR), which transcriptionally upregulates CYP3A4, CYP2C9, CYP2C19, and P-glycoprotein (P-gp). [5]

Magnitude of CYP3A4 Induction

A controlled crossover study (N=12) published in the European Journal of Clinical Pharmacology showed that 14 days of St. John's Wort (300 mg three times daily, standardized to 0.3% hypericin) reduced simvastatin AUC by 52% and simvastatin acid AUC by 62%. [6] Simvastatin is a prototypic CYP3A4 substrate, making this reduction a reliable proxy for the magnitude of induction one can expect with other CYP3A4-dependent drugs.

A separate pharmacokinetic trial found that St. John's Wort reduced cyclosporine plasma concentrations by 46 to 70%, contributing to documented organ rejection episodes in transplant patients. [7] The World Health Organization issued a safety communication on this interaction in 2000. [8]

P-glycoprotein Induction Is Also Relevant

P-gp induction by hyperforin means that drugs which are P-gp substrates, including certain antiretrovirals, digoxin, and direct oral anticoagulants, may have reduced bioavailability when St. John's Wort is co-administered. [5] Inclisiran itself is not documented as a P-gp substrate, so this is not a direct concern for the pair, but it matters for the broader medication list.

The Direct Inclisiran + St. John's Wort Interaction: What the Evidence Shows

Because inclisiran bypasses CYP3A4 entirely, St. John's Wort cannot reduce its plasma exposure through enzyme induction. No published pharmacokinetic study has shown a clinically meaningful interaction between inclisiran and any CYP3A4 inducer. [2]

The table below summarizes the interaction framework for assessing this pair:

| Interaction Vector | Relevant to Inclisiran? | Relevant to Co-Prescriptions? | |---|---|---| | CYP3A4 induction | No | Yes (statins, some anticoagulants) | | CYP2C9 induction | No | Yes (warfarin) | | P-gp induction | No (inclisiran not a P-gp substrate) | Yes (digoxin, DOACs) | | Serotonergic additive effect | No | Possible (if patient is on SSRIs) | | Cardiovascular pharmacodynamics | Indirect only | Monitor LDL-C and BP trend |

From a strict pharmacokinetic standpoint, St. John's Wort does not alter inclisiran's efficacy or safety profile directly.

Why the Full Medication List Is the Real Risk Zone

Most patients on Leqvio are also prescribed one or more of the following: a high-intensity statin, ezetimibe, a PCSK9 monoclonal antibody (in rare combination protocols), antihypertensives, anticoagulants, or antiplatelet agents. St. John's Wort interacts clinically with several drugs commonly co-prescribed with inclisiran.

Statins and St. John's Wort

Atorvastatin and simvastatin are CYP3A4 substrates. The 52% reduction in simvastatin AUC documented by Sugimoto et al. [6] means that a patient on simvastatin who starts St. John's Wort without adjusting their dose could lose a substantial portion of their LDL-lowering efficacy. The American Heart Association has noted that herbal CYP inducers can undermine statin pharmacotherapy in high-risk patients. [9]

Rosuvastatin and pravastatin are not CYP3A4 substrates and are less affected by this interaction. If a patient insists on using St. John's Wort, switching to a non-CYP3A4 statin may mitigate the pharmacokinetic risk.

Warfarin and St. John's Wort

St. John's Wort is a well-documented inducer of warfarin metabolism via CYP2C9. A randomized crossover study (N=12) in the British Journal of Clinical Pharmacology showed that St. John's Wort reduced warfarin plasma levels and increased warfarin clearance, resulting in a mean INR reduction of 1.0 unit. [10] Patients taking warfarin for atrial fibrillation or a prior thromboembolic event who also use St. John's Wort are at real risk of subtherapeutic anticoagulation.

Antiarrhythmics and St. John's Wort

Digoxin exposure fell by 25% after 10 days of St. John's Wort in a study of 25 healthy volunteers, attributable primarily to P-gp induction. [11] Patients on digoxin for rate control who add St. John's Wort may experience inadequate rate control, a concern compounded by the fact that atrial fibrillation is prevalent among patients with established ASCVD.

Direct Oral Anticoagulants (DOACs)

Rivaroxaban and apixaban are both CYP3A4 and P-gp substrates. Published pharmacokinetic data show that strong CYP3A4/P-gp inducers reduce rivaroxaban AUC by approximately 50%, enough to render standard doses potentially subtherapeutic. [12] The FDA label for rivaroxaban (Xarelto) warns against co-administration with combined CYP3A4 and P-gp inducers, a category that includes St. John's Wort. [12]

Pharmacodynamic Considerations

Even absent a pharmacokinetic interaction with inclisiran itself, St. John's Wort may influence the cardiovascular context in which inclisiran is prescribed.

Mood, Serotonin, and Cardiac Risk

St. John's Wort inhibits reuptake of serotonin, dopamine, and norepinephrine to varying degrees. [5] Patients on selective serotonin reuptake inhibitors (SSRIs), sometimes prescribed in cardiac rehabilitation, face a small but real risk of serotonin syndrome when combining SSRIs with St. John's Wort. [13] The severity ranges from mild (tremor, diaphoresis) to life-threatening (hyperthermia, rigidity, rhabdomyolysis).

Blood Pressure and Sympathomimetic Tone

Some case series have reported mild increases in blood pressure with high-dose St. John's Wort formulations, though controlled data are limited. Given that many inclisiran-treated patients have concurrent hypertension, any upward blood pressure trend warrants monitoring.

Monitoring Protocol if Both Are Being Used

Clinicians managing patients who insist on continuing St. John's Wort alongside inclisiran-based therapy should follow this monitoring schedule:

LDL-C Monitoring

Inclisiran's label specifies LDL-C measurement at the 3-month post-initiation visit to confirm response. [1] If LDL-C reduction is less than 30% from baseline, reassess background statin adherence and dose before attributing inadequate response to St. John's Wort, since St. John's Wort should not directly blunt inclisiran efficacy. A reduction of less than 30% at month 3 in the ORION trials was uncommon, occurring in fewer than 15% of participants in ORION-11. [3]

INR Monitoring (Warfarin Patients)

If a patient is on warfarin and starts or stops St. John's Wort, INR should be rechecked within 5 to 7 days and dose-adjusted accordingly. [10] This is not an inclisiran-specific recommendation; it applies to any warfarin patient who changes St. John's Wort use.

Statin Efficacy Assessment

If the patient is on atorvastatin or simvastatin and adds St. John's Wort, an LDL-C level at 4 to 6 weeks may reveal whether the induction effect is clinically meaningful for that individual. Switching to rosuvastatin or pravastatin is a practical option if LDL-C rises. [9]

Dose and Formulation Variables for St. John's Wort

Not all St. John's Wort preparations carry the same induction risk. Hyperforin content drives PXR activation. Extracts standardized to 3 to 5% hyperforin produce strong CYP3A4 induction; preparations with <1% hyperforin (such as Ze 117, used in some European mood-disorder studies) show substantially less induction in pharmacokinetic modeling. [14]

A 2019 review in the British Journal of Clinical Pharmacology concluded that "the extent of CYP3A4 induction by St. John's Wort is highly dependent on hyperforin content, with low-hyperforin preparations causing minimal pharmacokinetic interactions in controlled studies." [14] Patients who obtain St. John's Wort from unregulated sources cannot reliably know the hyperforin content of their product.

What to Tell Your Prescriber

Patients using St. John's Wort should disclose this to their Leqvio-prescribing clinician at every visit. The disclosure allows the care team to:

1. Check whether any co-prescribed medication is a CYP3A4 or P-gp substrate.
2. Switch the statin to a non-CYP3A4-dependent agent if indicated.
3. Increase INR monitoring frequency if the patient is on warfarin.
4. Screen for serotonin syndrome risk if an SSRI is co-prescribed.
5. Verify LDL-C response at the standard 3-month mark.

The Endocrine Society's 2023 clinical practice guidelines on lipid management state that "clinicians should routinely inquire about dietary supplement use in all patients receiving pharmacological lipid-lowering therapy, as several supplements significantly alter the pharmacokinetics of co-administered agents." [15]

Special Populations

Patients with Familial Hypercholesterolemia

Heterozygous familial hypercholesterolemia (HeFH) affects approximately 1 in 250 adults in the United States, according to the American Heart Association. [9] In this population, the LDL-lowering achieved by inclisiran is non-negotiable from a cardiovascular outcome standpoint. Any supplement that reduces the efficacy of a co-prescribed statin, St. John's Wort included, carries heightened clinical weight in HeFH patients compared with the general population.

Elderly Patients

Adults over 65 years accounted for 39% of participants in ORION-11 and showed comparable LDL-C reductions to younger cohorts. [3] This age group is also more likely to be on polypharmacy, warfarin, digoxin, antidepressants, making the indirect St. John's Wort interaction risk more clinically meaningful than in younger patients.

Patients on Immunosuppressants Post-Transplant

Cardiac transplant patients sometimes receive inclisiran for post-transplant hyperlipidemia. St. John's Wort is formally contraindicated in patients on cyclosporine, tacrolimus, or mycophenolate due to documented transplant rejection episodes linked to CYP3A4 induction. [7] The WHO flagged this risk explicitly in their 2000 advisory. [8]

Summary of the Risk Matrix

The direct pharmacokinetic interaction between inclisiran and St. John's Wort is low-risk. The indirect risk through the broader cardiovascular medication list is real and in some cases, particularly warfarin, cyclosporine, and CYP3A4-metabolized statins, clinically serious. Prescribers should review the full medication list at every inclisiran visit and document St. John's Wort status in the chart.

Patients who want to continue St. John's Wort alongside Leqvio should have an LDL-C panel at the 3-month standard checkpoint (per the ORION protocol [3]), an INR check within one week of any change in St. John's Wort use if warfarin is also prescribed, and a statin-appropriateness review favoring rosuvastatin or pravastatin over atorvastatin or simvastatin.