Bivalirudin

Bivalirudin is a 20-residue analogue of hirudin, the anticoagulant from medicinal leech saliva. Its D-Phe-Pro-Arg-Pro N-terminus occupies thrombin's active site while a glycine linker and an acidic C-terminal tail bind exosite I, giving bivalent, high-affinity inhibition. Unlike heparin it does not require antithrombin III as a cofactor and it inhibits clot-bound as well as free thrombin. Inhibition is reversible and self-limiting because thrombin slowly cleaves the Arg-Pro bond in the inhibitor itself, which is why anticoagulation fades within an hour of stopping the infusion.

Targets: Thrombin (factor IIa) active site, Thrombin exosite I

• · 0.75 mg/kg IV bolus, then 1.75 mg/kg/hour infusion. Weight-based, so no fixed microgram dose applies. Infusion rate is cut to about 1 mg/kg/hour in severe renal impairment and 0.25 mg/kg/hour on dialysis.
• · 0.75 mg/kg bolus then 1.75 mg/kg/hour. Bivalirudin does not cross-react with heparin-PF4 antibodies, which is the whole reason it is chosen here.

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• commonBleeding, including access-site haematoma— Still meaningfully less than with heparin plus a GPIIb/IIIa inhibitor, which is bivalirudin's main selling point.
• commonBack pain, nausea, hypotension, headache— Reported in the procedural setting and often hard to separate from the procedure itself.
• uncommonAcute stent thrombosis in the first 24 hours after PCI— A real signal in the trials; the reason many operators continue a post-PCI infusion.
• uncommonThrombocytopenia— Not immune-mediated in the way heparin-induced thrombocytopenia is.
• rareHypersensitivity or anaphylaxis

• Active major bleeding - there is no reversal agent for bivalirudin.
• Known hypersensitivity to bivalirudin or hirudins.
• Severe uncontrolled hypertension or recent intracranial surgery or haemorrhage, where any anticoagulant is unsafe.
• Severe renal impairment without dose reduction - clearance falls sharply and bleeding risk rises.

• cautionheparin — Overlapping anticoagulation raises bleeding risk; bivalirudin is generally used instead of heparin, not alongside it.
• cautioneptifibatide — Adding a GPIIb/IIIa inhibitor erases much of bivalirudin's bleeding advantage; reserved for bail-out thrombotic situations.
• cautionwarfarin — Bivalirudin prolongs the INR, which confuses the transition to oral anticoagulation.

• · Activated clotting time (ACT) around 5 minutes after the bolus in complex or prolonged procedures.
• · Haemoglobin, haematocrit and platelet count.
• · Serum creatinine and creatinine clearance to set the infusion rate.
• · Direct inspection of the arterial access site for haematoma or expanding swelling.

FDA- and EMA-approved prescription drug for hospital use. Not available outside clinical settings and not sold on the research-chemical market.

• Angiomax (bivalirudin) FDA prescribing information (label)
• Stone et al. 2008, HORIZONS-AMI, bivalirudin during primary PCI (trial)
• Valgimigli et al. 2015, MATRIX, bivalirudin versus heparin in acute coronary syndromes (trial)
• Erlinge et al. 2017, VALIDATE-SWEDEHEART (trial)

Bivalirudin is a bivalent thrombin inhibitor, and the bivalency is the whole story. The D-Phe-Pro-Arg N-terminus slots into the catalytic cleft of thrombin, mimicking the fibrinogen cleavage site, while the acidic C-terminal tail binds exosite 1, the docking groove thrombin uses to grip fibrinogen, PAR-1 and factor V. Because it occupies both sites, it inhibits thrombin that is already bound inside a clot, which heparin cannot do: heparin works through antithrombin, and the heparin-antithrombin complex is too large to reach clot-bound thrombin, and is also neutralised by platelet factor 4 released from activated platelets. Bivalirudin is not neutralised by PF4 and does not need a cofactor. The consequence downstream is that fibrinogen is not cleaved to fibrin, factor XIII is not activated so the clot is not cross-linked, and PAR-1 on platelets is not cleaved, so thrombin-driven platelet activation stops as well. That last point is why bivalirudin monotherapy can substitute for heparin plus a GPIIb/IIIa blocker in many patients. The self-cleavage of the Arg3-Pro4 bond by the captured thrombin means the block decays on a timescale of tens of minutes, which is the pharmacological basis for the bleeding advantage and, at the same time, for the early stent-thrombosis signal when the infusion is stopped at the end of the case.

Two failure modes dominate. The first is acute stent thrombosis in the hours after primary PCI, because the drug clears in 25 minutes and, if the P2Y12 inhibitor has not taken effect yet, there is a window with no meaningful antithrombotic cover; this is handled by continuing a full-dose 1.75 mg/kg/h infusion for 2 to 4 hours after the case rather than stopping at the table. The second is dose stacking in renal failure, where a 25-minute half-life becomes 3.5 hours and the standard infusion rate produces a level nobody intended. Beyond that: it is not an answer to a patient already bleeding, there is no reversal agent, and haemodialysis only removes about a quarter of the drug.

• Thrombin (factor IIa) catalytic site

  Direct competitive occupancy of the active site, preventing fibrinogen cleavage. Slowly cleaved by the enzyme it inhibits, making the block reversible.

• Thrombin exosite 1 (fibrinogen-recognition exosite)

  The C-terminal tail anchors here, giving high effective affinity and access to clot-bound thrombin that antithrombin-dependent drugs cannot reach.

• HORIZONS-AMI Phase 3 · n=3602 · 4.3 weeks · 2008

  Co-primary endpoints of major bleeding and net adverse clinical events at 30 days in STEMI patients undergoing primary PCI. Bivalirudin alone beat heparin plus a GPIIb/IIIa inhibitor on bleeding, at the cost of an excess of acute stent thrombosis in the first 24 hours.

• MATRIX Phase 3 · n=7213 · 4.3 weeks · 2015

  Major adverse cardiovascular events and net adverse clinical events in acute coronary syndrome patients undergoing PCI. MACE was not significantly lower with bivalirudin than heparin (10.3 versus 10.9 percent).

• VALIDATE-SWEDEHEART Phase 4 registry-based randomised trial · n=6006 · 25.7 weeks · 2017

  Composite of all-cause death, myocardial infarction or major bleeding at 180 days in STEMI and NSTEMI patients treated with radial access and potent P2Y12 inhibitors without planned GPIIb/IIIa use. No significant difference between bivalirudin and heparin.

Anticoagulant effect is immediate on the bolus, with ACT above 300 seconds within about 5 minutes in essentially all patients at full dose. Effect decays over roughly two hours after the infusion stops in normal renal function, and coagulation parameters return to baseline within about an hour of that.

Bivalirudin is given with aspirin and a P2Y12 inhibitor essentially always; that combination is the design assumption of every trial above. Adding a GPIIb/IIIa inhibitor on top is what the drug was built to avoid, and doing it routinely throws away the bleeding advantage that is bivalirudin's only reliable edge. It is not combined with heparin by design, although a patient will usually have had heparin at the door, and that overlap is expected rather than dangerous. Fondaparinux plus bivalirudin makes no sense. Thrombolytics plus bivalirudin is a bleeding disaster outside a protocol.

Against heparin: less bleeding, more early stent thrombosis, no mortality difference in the modern radial-access, potent-P2Y12 era. Against argatroban, the other direct thrombin inhibitor in common use: argatroban is hepatically cleared and is the better choice in renal failure, bivalirudin is renally cleared and is the better choice in liver failure. Against the hirudins (lepirudin, desirudin): bivalirudin's self-cleavage makes it far more forgiving, and unlike the hirudins it does not provoke clinically important anti-drug antibodies.

Not a self-administered drug and not priced per month. It is billed per procedure as a hospital pharmacy item; generic bivalirudin has been available in the US since 2015 and per-case cost is now a fraction of what it was when Angiomax was on patent, which is part of why heparin's cost advantage over bivalirudin has narrowed.

• ?The label gives clearance and protein binding but does not publish a volume of distribution, so that field is null rather than guessed.
• ?Published Ki values for bivalirudin against thrombin are in the low nanomolar range but I did not resolve a primary source for a specific number in this session, so no affinity figure is stated.
• ?The exact magnitude of the HORIZONS-AMI acute stent thrombosis excess is quoted widely as roughly 1.3 versus 0.3 percent in the first 24 hours; I confirmed the trial and the direction of the signal but not those specific percentages.

• Bivalirudin during primary PCI in acute myocardial infarction Stone GW, Witzenbichler B, Guagliumi G, et al. (HORIZONS-AMI Trial Investigators), N Engl J Med, 2008 · PMID 18499566

  The trial that made bivalirudin standard in primary PCI, and the source of the acute stent thrombosis signal.

• Bivalirudin or unfractionated heparin in acute coronary syndromes Valgimigli M, Frigoli E, Leonardi S, et al., N Engl J Med, 2015 · PMID 26324049

  MATRIX. The largest head-to-head against heparin monotherapy; the ischaemic advantage disappears when GPIIb/IIIa inhibitors are not routinely added to heparin.

• Bivalirudin versus heparin monotherapy in myocardial infarction N Engl J Med, 2017 · PMID 28844201

  VALIDATE-SWEDEHEART. Contemporary practice with radial access and ticagrelor; no benefit either way.

• Bivalirudin versus heparin during PCI in NSTEMI: individual patient data meta-analysis of large randomized trials Bikdeli B, et al., Circulation, 2023 · PMID 37746717

  Pooled patient-level data for the NSTEMI subgroup, the cleanest current synthesis.

• Effect of post-primary percutaneous coronary intervention bivalirudin infusion on acute stent thrombosis: meta-analysis of randomized controlled trials Shah R, Rao SV, et al., JACC Cardiovasc Interv, 2016 · PMID 27318846

  Why a full-dose post-PCI infusion, rather than stopping at the end of the case, is how the stent thrombosis signal is managed.

• Parenteral anticoagulants: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines Garcia DA, Baglin TP, Weitz JI, Samama MM, Chest, 2012 · PMID 22315264

  Reference pharmacology for the direct thrombin inhibitor class alongside heparins.