Bivalirudin
Hirulog, Hirulog-8, BG-8967, bivalirudin trifluoroacetate
Bivalirudin is a synthetic 20-amino-acid peptide anticoagulant that blocks thrombin directly, without needing antithrombin as a cofactor. It was designed from the leech anticoagulant hirudin and is given by intravenous infusion during percutaneous coronary intervention and in acute coronary syndromes. It is a fully licensed medicine with a very large randomised evidence base.
Mechanism
Bivalirudin is a bivalent direct thrombin inhibitor. Its N-terminal D-Phe-Pro-Arg-Pro segment occupies the catalytic active site of thrombin, while its C-terminal dodecapeptide (an analogue of residues 53-64 of hirudin) binds exosite 1, the fibrinogen-recognition site. The two binding domains are joined by a flexible tetraglycine spacer, so a single molecule straddles thrombin and shuts down both substrate recognition and catalysis. The resulting inhibition constant is in the low nanomolar range.
Two features distinguish it pharmacologically from heparin. First, because it binds thrombin directly it does not require antithrombin III, and it inhibits clot-bound thrombin as effectively as free thrombin. Heparin-antithrombin complexes are sterically excluded from thrombin already incorporated into fibrin. Second, the inhibition is self-limiting: thrombin slowly cleaves the Arg3-Pro4 bond within the bound N-terminal segment, which restores thrombin's catalytic function and accounts for bivalirudin's short duration of action. Bivalirudin also does not bind platelet factor 4, so it cannot generate or aggravate the immune complexes responsible for heparin-induced thrombocytopenia. Elimination is by a combination of proteolysis and renal clearance, so the half-life lengthens substantially as glomerular filtration falls.
What the research shows
The pivotal evidence comes from a sequence of large randomised trials. ACUITY (13,819 patients with moderate-to-high-risk acute coronary syndromes) found bivalirudin monotherapy gave similar ischaemic event rates to heparin plus a glycoprotein IIb/IIIa inhibitor but roughly halved major bleeding (3.0% versus 5.7%). HORIZONS-AMI (3,602 patients with ST-elevation myocardial infarction undergoing primary PCI) reported lower 30-day net adverse clinical events (9.2% versus 12.1%), lower major bleeding (4.9% versus 8.3%) and lower cardiac mortality with bivalirudin, but an excess of acute stent thrombosis within the first 24 hours.
The picture changed once the comparator became heparin alone rather than heparin plus a glycoprotein IIb/IIIa inhibitor. HEAT-PPCI, a single-centre open-label trial in 1,829 randomised primary PCI patients (1,812 analysed), found more major adverse ischaemic events with bivalirudin (8.7% versus 5.7%, relative risk 1.52, p=0.01) and no bleeding advantage (3.5% versus 3.1%). MATRIX (7,213 patients) and VALIDATE-SWEDEHEART (6,006 patients, registry-based randomisation) both found no significant difference between bivalirudin and heparin for their composite primary endpoints. BRIGHT-4 (6,016 Chinese patients with STEMI) then reported that bivalirudin followed by a post-PCI high-dose infusion reduced the 30-day composite of all-cause death or BARC 3-5 major bleeding compared with heparin monotherapy (3.06% versus 4.39%), suggesting that the prolonged infusion, absent from the earlier neutral or negative trials, may be the key variable. Taken together, the trials indicate that bivalirudin's advantage is bleeding-related and depends heavily on what it is compared against and whether a post-procedural infusion is used.
Evidence assessment
High-quality evidence
Bivalirudin holds marketing authorisation in the UK, EU and US on the basis of multiple large multicentre randomised controlled trials involving tens of thousands of patients, and it appears in international revascularisation guidelines. All six trials cited below were verified against PubMed: titles, PMIDs, DOIs, years, journals, sample sizes and reported effect estimates all match the published records. The evidence is strong in quality but genuinely mixed in direction: bivalirudin consistently reduces bleeding compared with heparin plus a glycoprotein IIb/IIIa inhibitor, but head-to-head against heparin monotherapy the picture is unsettled. HEAT-PPCI favoured heparin, MATRIX and VALIDATE-SWEDEHEART found no difference, and BRIGHT-4 favoured bivalirudin when a post-procedural high-dose infusion was used. That is a well-studied drug with a contested place in therapy, not a poorly studied one.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
Bivalirudin for patients with acute coronary syndromes Preclinical only
Bivalirudin alone produced similar 30-day rates of composite ischaemia to heparin plus a GPIIb/IIIa inhibitor but significantly less major bleeding (3.0% versus 5.7%), giving a superior net clinical outcome.
Bivalirudin during primary PCI in acute myocardial infarction Preclinical only
Bivalirudin alone reduced 30-day net adverse clinical events (9.2% versus 12.1%) and major bleeding compared with heparin plus a GPIIb/IIIa inhibitor, but caused an early excess of acute stent thrombosis within 24 hours.
Unfractionated heparin versus bivalirudin in primary percutaneous coronary intervention (HEAT-PPCI): an open-label, single centre, randomised controlled trial Preclinical only
A negative result for bivalirudin: the composite of death, stroke, reinfarction or unplanned target lesion revascularisation occurred more often with bivalirudin (8.7%) than heparin (5.7%; relative risk 1.52, p=0.01), with no reduction in major bleeding (3.5% versus 3.1%, p=0.59).
Bivalirudin or unfractionated heparin in acute coronary syndromes Preclinical only
Null result: major adverse cardiovascular events (10.3% versus 10.9%, relative risk 0.94) and net adverse clinical events (11.2% versus 12.4%) did not differ significantly between bivalirudin and unfractionated heparin, and a post-PCI infusion did not improve the composite endpoint.
Bivalirudin versus heparin monotherapy in myocardial infarction Preclinical only
Null result: no significant difference between bivalirudin and heparin in the 180-day composite of death from any cause, myocardial infarction or major bleeding.
Bivalirudin plus a high-dose infusion versus heparin monotherapy in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention: a randomised trial Preclinical only
Bivalirudin with a post-PCI high-dose infusion for 2-4 hours reduced the 30-day composite of all-cause death or BARC 3-5 major bleeding compared with heparin monotherapy (3.06% versus 4.39%), with lower all-cause mortality (2.96% versus 3.92%) and lower major bleeding (0.17% versus 0.80%).
Safety
Bleeding is the dominant risk, as with any parenteral anticoagulant, though bivalirudin generally causes less bleeding than heparin combined with a glycoprotein IIb/IIIa inhibitor. There is no specific reversal agent; management of haemorrhage relies on stopping the infusion (helped by the short half-life), supportive measures and, if needed, haemodialysis or haemofiltration, which remove a meaningful fraction of the drug. Accumulation occurs in renal impairment and dosing must be adjusted accordingly.
An excess of acute stent thrombosis within the first 24 hours after primary PCI was seen in HORIZONS-AMI and in later meta-analyses; a post-procedural infusion appears to mitigate this and is the design feature that distinguished BRIGHT-4. Hypersensitivity and anaphylaxis are rare. Bivalirudin does not cross-react with heparin-PF4 antibodies, which is why it is used when heparin-induced thrombocytopenia is present or suspected. Thrombocytopenia, hypotension, back pain and nausea are reported during infusion. It is not a substance with any legitimate non-clinical or self-administered use. It is a hospital intravenous anticoagulant used with continuous monitoring of coagulation and access sites.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | Prescription-only medicine (POM). Licensed by the MHRA for use in patients undergoing percutaneous coronary intervention, and for adults with unstable angina or non-ST-elevation myocardial infarction planned for urgent or early intervention. Originally authorised centrally in the EU in September 2004; several generic bivalirudin products are now marketed in Great Britain. Hospital-only in practice. |
| United States | FDA-approved (December 2000) for use as an anticoagulant in patients undergoing percutaneous coronary intervention, including those with or at risk of heparin-induced thrombocytopenia and HIT with thrombosis syndrome. Multiple generic intravenous formulations are approved. |
| WADA (sport) | Not listed on the WADA Prohibited List. Anticoagulants are not performance-enhancing substances and are not banned in or out of competition. |
Questions
Heparin works indirectly: it must first bind antithrombin, and the resulting complex is too bulky to reach thrombin that is already trapped inside a clot. Bivalirudin binds thrombin directly at two sites, needs no cofactor, and inhibits clot-bound as well as free thrombin. It also does not interact with platelet factor 4, so it cannot cause heparin-induced thrombocytopenia. Its effect wears off within roughly half an hour in people with normal kidneys, whereas heparin can be reversed pharmacologically with protamine.
It depends on the comparison. Against heparin combined with a glycoprotein IIb/IIIa inhibitor, bivalirudin clearly reduces bleeding. That is the basis of its licence. Against heparin alone, the large trials disagree: HEAT-PPCI favoured heparin, MATRIX and VALIDATE-SWEDEHEART found no difference, and BRIGHT-4 favoured bivalirudin when a prolonged post-procedure infusion was given. Current practice varies between centres and countries for exactly this reason.
No specific reversal agent exists. Because the half-life is only around 25 minutes in normal renal function, stopping the infusion is usually sufficient. In severe bleeding, supportive transfusion is used, and haemodialysis or haemofiltration removes a substantial proportion of the drug. This becomes clinically important in renal impairment, where the half-life can extend to several hours.
Heparin-induced thrombocytopenia is caused by antibodies against complexes of heparin and platelet factor 4. Bivalirudin does not bind platelet factor 4 and does not form those complexes, so it can anticoagulate a patient whose immune system has been sensitised to heparin. This is a labelled indication in the United States for patients undergoing percutaneous coronary intervention.