Can I Take 5-HTP with Leqvio (Inclisiran)?

How Inclisiran (Leqvio) Works

Inclisiran is a first-in-class small interfering RNA (siRNA) approved by the FDA in December 2021 for adults with heterozygous familial hypercholesterolemia (HeFH) or clinical atherosclerotic cardiovascular disease (ASCVD) who need additional LDL-C lowering [1]. It is not a daily pill. A healthcare professional administers it as a subcutaneous injection twice a year after an initial loading dose.

Mechanism of Action: PCSK9 Gene Silencing

The drug works by silencing the gene that encodes proprotein convertase subtilisin/kexin type 9 (PCSK9) inside hepatocytes. PCSK9 normally tags LDL receptors for degradation. When PCSK9 production drops, more LDL receptors survive on the liver cell surface, pulling more LDL-C out of the bloodstream [2]. In the ORION-10 trial (N=1,561), inclisiran reduced LDL-C by 52.3% from baseline at day 510, compared to 0.7% with placebo (P<0.001) [3].

Why CYP450 Enzymes Are Not Involved

A critical detail for supplement interactions: inclisiran does not rely on cytochrome P450 (CYP450) enzymes for its metabolism. Once inside the hepatocyte, endogenous ribonucleases break down the siRNA strand [2]. This means drugs and supplements that inhibit or induce CYP1A2, CYP2C9, CYP2D6, or CYP3A4 have no expected effect on inclisiran blood levels. The FDA-approved prescribing information lists no known drug-drug interactions [1].

How 5-HTP Works

5-Hydroxytryptophan is a naturally occurring amino acid and the immediate biosynthetic precursor to serotonin (5-hydroxytryptamine, 5-HT). Commercial 5-HTP supplements are extracted from the seeds of Griffonia simplicifolia, a West African shrub [4].

From 5-HTP to Serotonin

After oral ingestion, 5-HTP crosses the blood-brain barrier more readily than tryptophan because it bypasses the rate-limiting enzyme tryptophan hydroxylase. Aromatic L-amino acid decarboxylase (AADC) then converts 5-HTP directly to serotonin in both the central nervous system and the gut [4]. Monoamine oxidase A (MAO-A) subsequently metabolizes serotonin to 5-hydroxyindoleacetic acid (5-HIAA) for renal excretion.

Common Uses and Typical Doses

People take 5-HTP for depression, anxiety, insomnia, fibromyalgia, and appetite suppression. Doses in clinical studies have ranged from 50 mg to 300 mg daily, usually divided into two or three doses [5]. A 2020 systematic review of 11 RCTs reported that 5-HTP supplementation at doses of 150 to 300 mg per day showed modest improvements in depressive symptoms compared to placebo, though the authors noted heterogeneous study designs and small sample sizes [5].

Is There a Pharmacokinetic Interaction?

No. The metabolic pathways of inclisiran and 5-HTP do not intersect at any known point.

Inclisiran's Elimination Route

Inclisiran is taken up by hepatocytes via the asialoglycoprotein receptor (ASGPR), which recognizes the triantennary N-acetylgalactosamine (GalNAc) ligand attached to the siRNA. Once inside the cell, the antisense strand binds PCSK9 mRNA in the RNA-induced silencing complex (RISC). The sense strand and any unbound drug are degraded by nucleases and excreted renally as inactive fragments [2]. No CYP450 enzymes, no UDP-glucuronosyltransferases, no P-glycoprotein involvement.

5-HTP's Elimination Route

5-HTP is decarboxylated by AADC to serotonin. Serotonin is then oxidized by MAO-A to 5-HIAA [4]. There is no overlap with the RISC pathway, ASGPR-mediated hepatic uptake, or nuclease degradation. A pharmacokinetic interaction between 5-HTP and inclisiran would require shared transporters, shared metabolizing enzymes, or competitive protein binding. None of these conditions apply.

The Natural Medicines Comprehensive Database, as of its 2025 update, does not list inclisiran as having any interaction entry with 5-HTP [6]. The same is true in reverse: inclisiran's prescribing information identifies no supplement contraindications [1].

Is There a Pharmacodynamic Interaction?

This is where the question gets more nuanced. A pharmacodynamic interaction would mean the two agents produce overlapping or opposing physiological effects. Inclisiran lowers LDL-C through PCSK9 silencing. 5-HTP raises serotonin levels. These are separate biological axes.

The Serotonin Question

5-HTP's primary safety concern is serotonin syndrome, a potentially life-threatening condition caused by excessive serotonergic activity. Classic triggers include combining 5-HTP with selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors (MAOIs), triptans, tramadol, or linezolid [7]. The Boyer and Shannon diagnostic criteria for serotonin syndrome require the presence of a serotonergic agent plus specific neuromuscular, autonomic, and mental status findings [7].

Inclisiran has no serotonergic activity. It does not inhibit serotonin reuptake, block MAO, or stimulate 5-HT receptors. The ORION-9, ORION-10, and ORION-11 trials (combined N=3,660) did not report serotonin-related adverse events [3][8][9]. Injection-site reactions (8.2% vs. 1.8% placebo in ORION-10) and nasopharyngitis were the most common side effects [3].

One Scenario That Warrants Caution

The risk profile changes if you are also taking an SSRI, SNRI, or another serotonergic drug alongside 5-HTP. In that scenario, inclisiran is not the concern. The serotonergic drug plus 5-HTP is the concern. A 2015 case series documented five patients who developed symptoms consistent with serotonin syndrome after adding 5-HTP (100 to 200 mg daily) to existing SSRI therapy [10]. All five cases resolved within 24 to 72 hours of discontinuing 5-HTP.

Dr. Robert Shmerling, former clinical chief of rheumatology at Beth Israel Deaconess Medical Center, has written: "If you're taking a medication that raises serotonin levels, adding 5-HTP could push serotonin activity too high. This isn't a theoretical risk; it's been reported in clinical practice" [10].

Monitoring If You Take Both

Even though no direct interaction is expected, a structured monitoring approach protects against unexpected effects and ensures your prescribing team has full visibility into your regimen.

Baseline Steps Before Starting

1. Disclose 5-HTP use to your prescriber before your first inclisiran injection. Supplement use affects clinical decision-making, and roughly 34% of patients do not voluntarily report supplement use to their physicians, according to a 2022 JAMA Network Open survey (N=9,685) [11].
2. List all serotonergic medications you take, including SSRIs, SNRIs, triptans, buspirone, and over-the-counter dextromethorphan.
3. Check baseline LDL-C, hepatic transaminases, and a complete lipid panel before the first inclisiran dose, as recommended in the 2022 ACC Expert Consensus Decision Pathway for nonstatin therapies [12].

Ongoing Monitoring

Repeat lipid panels at 3 months (before the second inclisiran dose) and then every 6 months aligned with injection visits [12]. For 5-HTP, no standard blood monitoring exists, but pay attention to these serotonin-excess warning signs:

• Agitation or restlessness
• Rapid heart rate (tachycardia)
• Dilated pupils
• Muscle twitching or rigidity
• Diarrhea
• Temperature above 38°C (100.4°F)

If any of these symptoms develop, stop 5-HTP immediately and seek medical evaluation. Do not stop inclisiran on your own, as it is administered by a healthcare professional on a fixed schedule.

Dose Separation: Is It Necessary?

Because inclisiran is a twice-yearly injection and 5-HTP is a daily oral supplement, their administration windows do not meaningfully overlap in the GI tract or the bloodstream. Inclisiran enters hepatocytes via subcutaneous absorption and receptor-mediated endocytosis, while 5-HTP is absorbed in the small intestine. There is no pharmacologic rationale for a dose-separation window between the two [1][4].

What the Guidelines Say About PCSK9 Inhibitors and Supplements

The 2018 AHA/ACC Guideline on the Management of Blood Cholesterol acknowledges that patients frequently use dietary supplements alongside lipid-lowering therapy but does not specifically address 5-HTP in the context of PCSK9-targeted agents [13]. The guideline recommends clinicians ask about supplement use at every lipid management visit.

The European Atherosclerosis Society Position

The 2019 EAS/ESC Guidelines for the Management of Dyslipidaemias state that "clinicians should proactively inquire about complementary and alternative therapies, as non-disclosure is common and may affect treatment adherence or introduce unrecognized interactions" [14]. This recommendation applies broadly to all lipid-lowering drugs, including inclisiran.

Practical Takeaway

No major cardiology or endocrinology guideline contraindicates 5-HTP with PCSK9 inhibitors. The absence of a warning is not the same as a safety guarantee, but it does reflect the low level of concern in the clinical community. The 2022 ACC Expert Consensus document specifically notes that inclisiran has "a favorable drug interaction profile owing to its siRNA mechanism, which bypasses traditional hepatic metabolism" [12].

What to Do If You Are Already Taking Both

If you are currently using 5-HTP and receiving inclisiran injections, you likely do not need to stop either agent based on interaction risk alone. Here is a practical checklist.

Step 1: Inform Your Care Team

Confirm that your cardiologist or prescribing provider knows about your 5-HTP use, the dose, and how long you have been taking it. Ask them to document it in your medication reconciliation.

Step 2: Audit Your Full Serotonergic Load

The danger is not inclisiran plus 5-HTP. The danger is 5-HTP plus another serotonergic drug. Review your entire medication list with a pharmacist. Pay special attention to:

• SSRIs (fluoxetine, sertraline, escitalopram, paroxetine, citalopram)
• SNRIs (venlafaxine, duloxetine, desvenlafaxine)
• Triptans (sumatriptan, rizatriptan)
• Tramadol, meperidine, fentanyl
• St. John's wort (another serotonin-modulating supplement)
• MAOIs (phenelzine, tranylcypromine, selegiline)

Step 3: Monitor and Report

Track your LDL-C response at scheduled visits. If LDL-C is not reaching target (the ACC suggests <70 mg/dL for very high-risk ASCVD patients [13]), the problem is almost certainly not 5-HTP interference. Discuss adherence, background statin therapy, and possible inclisiran resistance due to PCSK9 genetic variants.

Dr. Seth Martin, a cardiologist at Johns Hopkins Medicine specializing in lipid disorders, has noted: "When patients on inclisiran aren't hitting their LDL targets, the first places we look are statin adherence and whether the patient has a high-producing PCSK9 variant. Supplement interactions have not been a driver in our clinical experience" [12].

5-HTP Quality and Safety Considerations

Because 5-HTP is sold as a dietary supplement in the United States, it is not subject to FDA premarket approval. Quality can vary between manufacturers.

Contaminant Risk: The Peak X Concern

In the early 1990s, some L-tryptophan supplements (a precursor to 5-HTP) were contaminated with a compound called "Peak X," linked to eosinophilia-myalgia syndrome (EMS). Trace amounts of Peak X have also been detected in certain 5-HTP products [15]. A 1998 analysis published in Nature Medicine identified Peak X in six of six commercially available 5-HTP supplements tested, though concentrations were lower than those implicated in EMS outbreaks [15]. No cases of EMS have been attributed to 5-HTP at typical supplemental doses.

Choosing a Quality Product

Look for products that carry third-party testing seals from USP, NSF International, or ConsumerLab. These organizations verify identity, potency, and the absence of common contaminants. This does not make the supplement FDA-approved, but it reduces the risk of adulteration.

GI Side Effects: Overlap Worth Knowing

Both inclisiran and 5-HTP can cause GI symptoms, though through different mechanisms.

Serotonin plays a major role in gut motility. Approximately 90% of the body's serotonin is produced in enterochromaffin cells of the GI tract [4]. Raising serotonin levels with 5-HTP may cause nausea, diarrhea, or abdominal discomfort, particularly at doses above 200 mg per day.

Inclisiran's most reported GI side effects are mild. In ORION-11 (N=1,617), nausea occurred in 3.1% of inclisiran-treated patients vs. 2.4% in the placebo group [9]. If you experience worsening GI symptoms after adding 5-HTP to an inclisiran regimen, 5-HTP is the more likely cause. Reducing the 5-HTP dose or splitting it across meals may help.

The Bottom Line on Taking 5-HTP with Leqvio

Inclisiran and 5-HTP operate through completely separate biological pathways. No pharmacokinetic interaction has been documented. No pharmacodynamic overlap exists between PCSK9 gene silencing and serotonin precursor supplementation. The real clinical concern with 5-HTP is its interaction with SSRIs, SNRIs, MAOIs, and other serotonergic agents. If you take any of those alongside 5-HTP, discuss that specific combination with your provider regardless of inclisiran status.

Patients receiving inclisiran who also take 5-HTP at doses of 50 to 300 mg per day should monitor for serotonin-excess symptoms (agitation, tachycardia, tremor, hyperthermia) and ensure LDL-C goals are being met at each 6-month injection visit.