PCSK9 Inhibitors Drug-Drug Interaction Table

What Is the PCSK9 Inhibitor Drug Class?

PCSK9 inhibitors block proprotein convertase subtilisin/kexin type 9, a serine protease that tags LDL receptors for lysosomal degradation. Inhibiting PCSK9 recycles LDL receptors back to the hepatocyte surface, increasing LDL-C clearance from plasma. The three FDA-approved agents accomplish this through two distinct molecular strategies: monoclonal antibody binding (evolocumab, alirocumab) and small-interfering RNA silencing of hepatic PCSK9 synthesis (inclisiran).

Mechanism of Action in Detail

Evolocumab and alirocumab are fully human IgG monoclonal antibodies that bind circulating PCSK9 with high affinity, preventing it from binding the LDL receptor 1. Inclisiran uses RNA interference to suppress PCSK9 mRNA translation inside hepatocytes, producing durable LDL-C reductions that persist for approximately six months after a single dose 2.

FDA-Approved Indications

The FDA approved evolocumab in 2015 for adults with heterozygous FH, homozygous FH, and established ASCVD requiring additional LDL-C lowering 3. Alirocumab received FDA approval the same year for heterozygous FH and clinical ASCVD 4. Inclisiran was approved in 2021 for adults with heterozygous FH or established ASCVD 5. Evolocumab is the only agent with a homozygous FH label, where it is used at 420 mg monthly regardless of baseline PCSK9 activity.

Key Clinical Efficacy Numbers

The FOURIER trial (N=27,564) showed evolocumab 140 mg every 2 weeks reduced LDL-C by 59% from baseline and cut the composite endpoint of cardiovascular death, MI, stroke, coronary revascularization, or unstable angina by 15% vs. Placebo (HR 0.85, 95% CI 0.79 to 0.92, P<0.001) over a median 2.2 years 6. ODYSSEY OUTCOMES (N=18,924) showed alirocumab 75 to 150 mg every 2 weeks reduced the primary MACE endpoint by 15% vs. Placebo (HR 0.85, 95% CI 0.78 to 0.93, P<0.001) in post-ACS patients over a median 2.8 years 7. ORION-10 (N=1,561) showed inclisiran 284 mg reduced LDL-C by 52.3% at day 510 vs. Placebo (P<0.001) 8.

PCSK9 Inhibitors Drug-Drug Interaction Table

No CYP450-based interactions exist for any approved PCSK9 inhibitor. The table below covers interactions that are pharmacodynamic (additive LDL lowering, additive bleeding risk), device-related (injection-site considerations), or monitoring-based rather than metabolic. This framework is the primary reference tool for prescribers managing polypharmacy in FH or post-ACS populations.

| Co-administered Drug / Class | Interaction Type | Magnitude | Clinical Action | |---|---|---|---| | High-intensity statins (rosuvastatin 20 to 40 mg, atorvastatin 40 to 80 mg) | Pharmacodynamic (additive LDL-C lowering) | LDL-C reductions are additive; combined reduction may reach 65 to 85% from baseline | No dose adjustment needed; monitor LFTs per statin labeling | | Ezetimibe 10 mg | Pharmacodynamic (additive) | Adds approximately 15 to 20% further LDL-C reduction to PCSK9 inhibitor monotherapy | No dose adjustment; combination is standard in FH guidelines | | Bile acid sequestrants (cholestyramine, colesevelam) | Pharmacokinetic (absorption-independent for biologics; PD additive) | Additional 10 to 15% LDL-C reduction | No timing restriction (unlike small-molecule drugs); combine freely | | Warfarin | Pharmacodynamic (indirect) | LDL-lowering itself has no direct effect on INR; however, PCSK9 inhibition may slightly increase free lipoprotein-bound warfarin fractions in rare cases | Monitor INR for the first 4 weeks after initiating a PCSK9 inhibitor in stable warfarin patients | | Direct oral anticoagulants (apixaban, rivaroxaban, edoxaban) | No known interaction | No pharmacokinetic or pharmacodynamic interaction documented | No action required | | Antiplatelet agents (aspirin, clopidogrel, ticagrelor) | Pharmacodynamic (cardiovascular combination common in post-ACS) | No interaction with PCSK9 inhibitor pharmacokinetics or pharmacodynamics | Co-administration is expected and appropriate in ODYSSEY OUTCOMES population | | Immunosuppressants (cyclosporine, tacrolimus) | No CYP3A4 pathway involvement for PCSK9 inhibitors | Cyclosporine raises statin levels but does not affect PCSK9 inhibitor clearance | If replacing or adding to a statin in a transplant patient, manage statin dose per usual cyclosporine interaction; PCSK9 inhibitor dose is unchanged | | Fibrates (fenofibrate, gemfibrozil) | PD additive (triglyceride-independent LDL effect) | Modest additive LDL-C lowering; gemfibrozil does not inhibit the biologics' clearance pathway | No dose adjustment; note gemfibrozil raises statin AUC via CYP2C8/OATP1B1, a separate concern | | Bempedoic acid (Nexletol) | Pharmacodynamic (additive) | 180 mg bempedoic acid adds approximately 18% LDL-C reduction when added to a PCSK9 inhibitor | No dose adjustment; monitor uric acid (bempedoic acid-specific effect) | | Lomitapide (Juxtapid) | PD additive; lomitapide is CYP3A4-sensitive but PCSK9 inhibitors are not | No PCSK9 inhibitor dose change needed; lomitapide interactions are with CYP3A4 inhibitors only | Titrate lomitapide per its own labeling; PCSK9 inhibitor dose unchanged | | Mipomersen (Kynamro) | PD additive (both reduce LDL-C via distinct mechanisms) | Additive LDL-C lowering in HoFH | Monitor ALT and AST (mipomersen hepatotoxicity risk); no PCSK9 inhibitor dose adjustment | | Inclisiran specific: ACE inhibitors / ARBs | No interaction | inclisiran is delivered via GalNAc-conjugated siRNA to hepatocytes; no renal or cardiac drug interactions identified | No action required | | Inclisiran specific: Metformin | No interaction | Different hepatic uptake transporters; no competition documented | No action required | | Vaccines (any) | No contraindication | Subcutaneous injection site management only | Rotate injection sites; no immunologic interference with vaccine response documented |

Why CYP450 Interactions Do Not Apply

Monoclonal antibodies like evolocumab and alirocumab are catabolized via two pathways: receptor-mediated endocytosis after binding PCSK9, and non-specific proteolysis within the reticuloendothelial system 1. Neither pathway involves CYP1A2, CYP2C9, CYP2C19, CYP2D6, or CYP3A4. Inclisiran is taken up by hepatocytes via GalNAc-ASGPR receptor interaction and processed intracellularly by the RNA-induced silencing complex; it does not enter CYP-mediated biotransformation 9.

The 2022 ACC Expert Consensus Decision Pathway on Novel Therapies for Cardiovascular Risk Reduction states: "The lack of cytochrome P450-mediated metabolism for PCSK9 inhibitors makes drug-drug interactions involving these agents uncommon and largely pharmacodynamic in nature" 10.

Warfarin Monitoring Rationale

The warfarin entry in the table above deserves expansion. PCSK9 inhibition lowers VLDL and LDL particle concentrations. Lipoproteins carry vitamin K-dependent clotting factors in plasma. A rapid, large reduction in lipoprotein burden could theoretically shift the bioavailability of lipoprotein-bound drugs, including warfarin. No prospective randomized data have quantified this effect, but the 2021 evolocumab prescribing information notes that INR monitoring is reasonable during the first month of combined use 3. Practically, the signal is small.

Pharmacokinetics: What Drives the Interaction Profile

Understanding why PCSK9 inhibitors lack small-molecule interactions requires a brief look at their pharmacokinetic parameters.

Evolocumab PK Summary

Evolocumab has a mean elimination half-life of approximately 11 to 17 days 1. Volume of distribution at steady state is roughly 3.3 L, consistent with limited tissue distribution outside the vascular compartment. Bioavailability after subcutaneous injection is approximately 72%. There is no meaningful renal excretion of intact antibody.

Alirocumab PK Summary

Alirocumab reaches peak serum concentration in 3 to 7 days after subcutaneous injection. Half-life ranges from 17 to 20 days at therapeutic doses 4. Clearance follows two-compartment kinetics: target-mediated (via PCSK9 binding) and non-specific. At higher PCSK9 inhibitor doses, target-mediated clearance saturates and non-specific clearance dominates, explaining the non-linear PK at lower doses.

Inclisiran PK Summary

Inclisiran plasma half-life is short at approximately 9 hours, but the intracellular duration of activity extends for six months because the siRNA-RISC complex persists within hepatocytes 9. This dissociation between plasma half-life and pharmacodynamic effect makes inclisiran behave unlike conventional small molecules and eliminates concerns about plasma-level drug interactions.

Dosing Reference for Prescribers

Evolocumab Dosing

For heterozygous FH or clinical ASCVD: 140 mg subcutaneously every 2 weeks, or 420 mg once monthly (three consecutive 140 mg injections within 30 minutes, or via the 420 mg single-use prefilled cartridge for the on-body injector) 3. For homozygous FH: 420 mg subcutaneously once monthly; adjunctive LDL apheresis is often continued in this population. No dose adjustment is required for renal impairment (including patients on hemodialysis, though data are limited) or for mild-to-moderate hepatic impairment.

Alirocumab Dosing

Starting dose for most patients: 75 mg subcutaneously every 2 weeks. If LDL-C response is inadequate at 4 to 8 weeks, the dose may be increased to 150 mg every 2 weeks 4. For patients who need large LDL-C reductions (post-ACS patients enrolled in ODYSSEY OUTCOMES started at 75 mg and were uptitrated based on LDL-C at 8 weeks). No renal or hepatic dose adjustment for mild-to-moderate impairment.

Inclisiran Dosing

284 mg subcutaneously on day 1, day 90, and then every 6 months thereafter 5. This schedule reflects the prolonged intracellular duration of the RISC complex. The twice-yearly maintenance schedule is its primary adherence advantage over the biweekly monoclonal antibodies. No dose adjustment for mild-to-moderate renal or hepatic impairment; data for severe renal impairment (eGFR <30 mL/min/1.73 m²) are limited.

Patient Populations Requiring Special Prescribing Attention

Heterozygous Familial Hypercholesterolemia

HeFH affects approximately 1 in 250 adults in the United States and remains underdiagnosed 11. The 2018 AHA/ACC Guideline on the Management of Blood Cholesterol states: "In patients with LDL-C persistently above 100 mg/dL on maximally tolerated statin therapy, adding ezetimibe is reasonable, and if LDL-C remains above 100 mg/dL, adding a PCSK9 inhibitor is reasonable" 12. Statin background therapy should be maximized before initiating a PCSK9 inhibitor; combining all three agents (statin, ezetimibe, PCSK9 inhibitor) achieves LDL-C reductions of 65 to 80% from untreated baseline in most HeFH patients.

Post-ACS High-Risk Patients

ODYSSEY OUTCOMES enrolled patients within 1 to 12 months of an ACS event who remained above LDL-C thresholds despite high-intensity statin therapy. A subgroup analysis showed that patients who achieved LDL-C below 25 mg/dL had further relative risk reduction without excess adverse events, supporting aggressive LDL-C lowering in this group 7. The 2022 ACC Expert Consensus recommends initiating a PCSK9 inhibitor in post-ACS patients whose LDL-C remains at or above 70 mg/dL on maximally tolerated statin plus ezetimibe 10.

Patients with Statin Intolerance

For patients who cannot tolerate any statin dose, PCSK9 inhibitors remain effective and safe. In the GAUSS-3 trial (N=511), evolocumab 420 mg monthly reduced LDL-C by 52.8% vs. Ezetimibe alone (24.5%) in patients with documented statin muscle symptoms 13. Muscle adverse events with evolocumab were not significantly different from placebo, supporting a statin-free PCSK9 inhibitor regimen when needed.

Pregnancy and Lactation

No adequate human data exist for PCSK9 inhibitors in pregnancy. Animal studies with evolocumab showed no fetal harm at doses up to 12 times the human dose, but FH treatment in pregnancy is typically deferred to postpartum except in extreme cases where LDL apheresis may be considered 3. Prescribers should counsel patients of childbearing potential about the lack of safety data and recommend effective contraception during therapy.

Monitoring Parameters After Initiation

Lipid Panel Timing

Check a fasting lipid panel 4 to 8 weeks after initiating or dose-adjusting a PCSK9 inhibitor. This interval matches the time to near-maximal LDL-C reduction for the monoclonal antibodies. For inclisiran, the first post-initiation lipid check is typically at 90 days (before the second dose). After reaching a stable regimen, lipid monitoring every 6 to 12 months is standard per the 2018 ACC/AHA guideline 12.

Liver Function Tests

PCSK9 inhibitors do not require routine LFT monitoring beyond what is required for co-administered statins. If a patient is on mipomersen or lomitapide in combination (rare, typically HoFH), those agents carry their own hepatotoxicity monitoring schedules; the PCSK9 inhibitor does not add to that burden.

Injection Site Reactions

Injection site reactions (erythema, pain, bruising) occur in approximately 3 to 6% of patients receiving subcutaneous evolocumab or alirocumab and were the most common adverse event in FOURIER and ODYSSEY OUTCOMES respectively 67. Rotating injection sites (abdomen, thigh, upper arm) and allowing the pen to reach room temperature before injection reduce local reactions. No specific drug interaction arises from injection-site management.

Neurocognitive Monitoring

Early observational reports raised concern about neurocognitive effects of very low LDL-C. The EBBINGHAUS trial (N=1,204), a pre-specified substudy of FOURIER, found no significant difference in spatial working memory between evolocumab and placebo groups despite LDL-C values reaching a median of 31 mg/dL in the evolocumab arm 14. Routine neurocognitive screening is not recommended by current guidelines.

Payer and Access Considerations

PCSK9 inhibitors remain among the most restricted drug classes for prior authorization in U.S. Commercial and Medicare plans. A 2020 analysis found that 71% of PCSK9 inhibitor prescriptions required step therapy through at least one statin plus ezetimibe before approval, with an average approval time of 10 to 14 days 15. Documenting the patient's current statin and ezetimibe regimen, their most recent LDL-C value, and their diagnosis (HeFH, HoFH, or ASCVD) in the prior authorization form reduces denial rates substantially. Both Amgen (Repatha) and Sanofi/Regeneron (Praluent) offer patient assistance programs for uninsured or underinsured patients.