Can I Take St. John's Wort with Lisinopril?

Why This Question Matters for People on Lisinopril

Lisinopril is the most prescribed ACE inhibitor in the United States, with over 87 million dispensed prescriptions annually according to ClinCalc drug usage statistics based on MEPS survey data. St. John's Wort (Hypericum perforatum) is among the top-selling herbal supplements in the U.S., frequently used for mild-to-moderate depression [1]. When patients on antihypertensives search for natural mood support, this combination comes up often.

The Core Concern

St. John's Wort is one of the most potent herbal enzyme inducers known. It upregulates cytochrome P450 3A4 (CYP3A4), CYP2C9, CYP1A2, and the efflux transporter P-glycoprotein (P-gp) [2]. These pathways handle the metabolism of roughly half of all prescription drugs. That enzyme-inducing profile is why the FDA lists St. John's Wort as a clinically significant CYP3A4 inducer on its official drug interaction tables.

Why Lisinopril Is an Exception

Lisinopril stands apart from most cardiovascular drugs because it undergoes essentially zero hepatic metabolism. It is absorbed intact, circulates without binding to plasma proteins, and is excreted unchanged by the kidneys [3]. Because CYP enzymes are not involved in its clearance, St. John's Wort's induction of CYP3A4 or CYP2C9 has no meaningful pathway to alter lisinopril blood levels. A pharmacokinetic review published in Clinical Pharmacokinetics confirmed that lisinopril's renal clearance makes it largely immune to CYP-mediated drug interactions [4].

Pharmacokinetic Profile: Lisinopril vs. St. John's Wort's Enzyme Effects

The interaction potential of any drug pair depends on whether one compound alters the absorption, metabolism, or excretion of the other. For lisinopril and St. John's Wort, the overlap is minimal on paper, but the clinical picture is more nuanced than a single drug pair.

How St. John's Wort Changes Drug Metabolism

Hyperforin, the principal bioactive constituent in St. John's Wort, activates the pregnane X receptor (PXR), which in turn transcriptionally upregulates CYP3A4, CYP2C9, CYP2C19, and the MDR1 gene encoding P-glycoprotein [2]. This induction reaches steady state within about 10 to 14 days of consistent dosing at 300 mg three times daily (standardized to 0.3% hypericin). The magnitude of CYP3A4 induction can reduce substrate drug AUC (area under the curve) by 50% or more, as documented in the landmark cyclosporine interaction studies [5].

Lisinopril's Metabolic Pathway

Lisinopril is the lysine analog of enalaprilat. Unlike enalapril (a prodrug requiring hepatic conversion), lisinopril is already in its active diacid form at the time of ingestion. Its oral bioavailability is approximately 25%, and the absorbed fraction is eliminated entirely by the kidneys with a half-life of about 12 hours [3]. No metabolites have been identified in human urine or plasma. The FDA-approved prescribing information for lisinopril confirms that it "does not undergo metabolism" and "is excreted unchanged entirely in the urine."

Net Direct Risk

Because St. John's Wort's interaction mechanism is CYP and P-gp induction, and lisinopril bypasses both pathways, the direct pharmacokinetic interaction risk is low. A 2012 systematic review of herbal-drug interactions in British Journal of Clinical Pharmacology noted that ACE inhibitors cleared renally (lisinopril, enalaprilat) carry substantially lower interaction risk with enzyme inducers compared to hepatically metabolized ACE inhibitors such as ramipril or fosinopril [6].

The Indirect Risk: Other Drugs in Your Regimen

Here is where the clinical danger actually lives. Patients taking lisinopril rarely take it alone. Common co-prescribed medications include amlodipine, atorvastatin, warfarin, hydrochlorothiazide, and metoprolol. Several of these are CYP3A4 or CYP2C9 substrates, and St. John's Wort can reduce their plasma concentrations enough to cause therapeutic failure.

Documented High-Risk Co-Medications

A meta-analysis of St. John's Wort drug interactions published in Clinical Pharmacology & Therapeutics identified the following cardiovascular drugs as having clinically significant interactions [7]:

| Co-prescribed Drug | Metabolic Pathway | Effect of St. John's Wort | Clinical Consequence | |---|---|---|---| | Warfarin | CYP2C9, CYP3A4 | AUC reduced ~25% | INR drop, clot risk | | Atorvastatin | CYP3A4 | AUC reduced ~50% | Loss of LDL control | | Amlodipine | CYP3A4 | AUC reduced ~30 to 40% | BP rebound | | Digoxin | P-gp substrate | AUC reduced ~25% | Heart failure decompensation | | Clopidogrel | CYP2C19 (prodrug) | Complex; activation may increase | Bleeding risk change |

A randomized crossover trial in 12 healthy volunteers showed that 14 days of St. John's Wort (900 mg/day) reduced the AUC of simvastatin by 48% (P<0.001) through CYP3A4 induction [8]. The same mechanism applies to atorvastatin and lovastatin. If you take lisinopril plus a statin, introducing St. John's Wort could silently erode your lipid control.

The Amlodipine Concern

The lisinopril-amlodipine combination is extremely common; it is marketed as a fixed-dose pill (Prestalia). A pharmacokinetic study published in the Journal of Clinical Pharmacology demonstrated that St. John's Wort reduced amlodipine AUC by 37% in healthy adults [9]. This could raise blood pressure in patients who are stable on the combination, potentially prompting unnecessary dose escalation.

Blood Pressure Effects of St. John's Wort Itself

Separate from enzyme induction, St. John's Wort may have direct cardiovascular effects. Data here are mixed and modest.

Evidence for Blood Pressure Changes

A randomized, double-blind trial of St. John's Wort for major depression (N=340) found no significant change in systolic or diastolic blood pressure versus placebo over 8 weeks [10]. A smaller pharmacovigilance analysis in the WHO VigiBase database identified scattered reports of both hypertension and hypotension associated with St. John's Wort, though causality was not established [11].

Serotonergic Considerations

St. John's Wort inhibits reuptake of serotonin, norepinephrine, and dopamine [1]. If a patient on lisinopril is also taking an SSRI or SNRI (common in cardiac patients with comorbid depression), adding St. John's Wort raises the risk of serotonin syndrome. The FDA's safety communication on serotonergic drug interactions emphasizes that serotonin syndrome can present with hypertension, hyperthermia, and autonomic instability. This is not a lisinopril interaction per se, but it becomes clinically relevant in the same patient population.

What to Do If You Are Already Taking Both

If you have been using St. John's Wort alongside lisinopril (and potentially other medications), abrupt discontinuation of the herb carries its own risk.

The Rebound Problem

Stopping St. John's Wort reverses CYP3A4 induction over roughly 7 to 14 days. During this washout, plasma levels of co-prescribed CYP3A4 substrates will rise. A case report in The Annals of Pharmacotherapy documented supratherapeutic cyclosporine levels and acute nephrotoxicity after a transplant patient stopped St. John's Wort abruptly [12]. The same de-induction rebound applies to any CYP3A4-metabolized cardiovascular drug in your regimen.

Recommended Steps

1. Do not stop St. John's Wort abruptly if you are on CYP3A4-substrate medications. Taper over 1 to 2 weeks under prescriber guidance.
2. Bring the bottle to your next appointment. Clinicians need the exact product name and dose to assess your interaction risk.
3. Monitor blood pressure at home twice daily (morning and evening) for at least 2 weeks after any change in St. John's Wort dosing.
4. Request a medication reconciliation. The American Heart Association recommends asking your pharmacist to review all prescription and over-the-counter products for interactions [13].

Monitoring and Dose-Separation Guidance

For the lisinopril-St. John's Wort pair specifically, dose separation (taking them hours apart) offers no pharmacokinetic advantage because the interaction mechanism is enzyme induction, not absorption competition. CYP induction is a systemic, sustained effect that persists as long as the herb is in your system.

Lab Monitoring

If you and your clinician decide the combination is acceptable after reviewing your full medication list, the following labs should be checked at baseline and at 4 to 6 weeks [4]:

• Basic metabolic panel (BMP) with creatinine and potassium (standard for ACE inhibitor monitoring)
• Fasting lipid panel (if on a statin)
• INR (if on warfarin)
• Digoxin trough level (if applicable)

When the Combination Is Reasonable

A patient who takes lisinopril as monotherapy for mild hypertension, is not on any CYP3A4-substrate co-medications, and has discussed St. John's Wort use with their prescriber faces low pharmacokinetic risk. A 2015 review in the World Journal of Cardiology concluded that renally cleared cardiovascular drugs pose the lowest interaction liability with herbal CYP inducers [14].

When to Avoid It Entirely

You should not combine St. John's Wort with lisinopril regimens that include warfarin, digoxin, atorvastatin, simvastatin, lovastatin, amlodipine, nifedipine, or any calcineurin inhibitor. The Natural Medicines Comprehensive Database rates St. John's Wort interactions with CYP3A4 substrates as "major" severity, meaning the combination should generally be avoided [15].

Alternatives to St. John's Wort for Patients on Lisinopril

If mood support is the goal, options with lower interaction profiles exist.

Evidence-Based Alternatives

SAMe (S-adenosylmethionine): A Cochrane review found SAMe comparable to tricyclic antidepressants for mild-to-moderate depression, with no CYP induction activity [16]. Typical doses range from 400 to 1,600 mg/day.

Cognitive behavioral therapy (CBT): The AHA's 2021 scientific statement on psychological health and cardiovascular disease endorsed CBT as first-line for depression in cardiac patients, noting it carries zero pharmacokinetic interaction risk [13].

Omega-3 fatty acids (EPA-predominant): A 2019 meta-analysis in Translational Psychiatry (N=2,240 across 26 RCTs) found EPA-predominant omega-3 formulations produced a small but significant antidepressant effect (SMD=0.28, 95% CI 0.10 to 0.47) [17]. EPA does not induce CYP enzymes and may confer additional cardiovascular benefit.

The Bottom Line on Safety

The direct pharmacokinetic interaction between St. John's Wort and lisinopril is clinically insignificant because lisinopril is eliminated renally without CYP involvement [3]. The real hazard is polypharmacy: St. John's Wort potently induces CYP3A4, CYP2C9, and P-glycoprotein, which can slash blood levels of statins, calcium channel blockers, warfarin, and digoxin that are commonly prescribed alongside lisinopril [7]. Before adding St. John's Wort, get a complete interaction check on every medication in your regimen, not just the ACE inhibitor.