Hirudin
Also known as: r-hirudin, recombinant hirudin, lepirudin (Refludan), desirudin (Iprivask / Revasc), PEG-hirudin, natural hirudin (Hirudo medicinalis), direct thrombin inhibitor (bivalent)
Direct thrombin inhibitor — naturally occurring 65-amino-acid peptide (and recombinant derivatives); anticoagulant agent
What it is
If you need powerful, predictable blood-clot prevention — especially when heparin has caused a dangerous immune reaction — hirudin and its recombinant forms are the gold-standard alternatives. Originally from medicinal leech saliva, they block the clotting enzyme thrombin directly, with decades of clinical evidence supporting their use.
The scientific side
hirudin is a 65-amino-acid peptide originally isolated from the salivary glands of the medicinal leech Hirudo medicinalis, and it functions as the most potent and specific known natural inhibitor of thrombin, a serine protease that plays a pivotal regulatory role in hemostasis and blood coagulation. Hirudin is classified as a bivalent direct thrombin inhibitor (DTI): it simultaneously engages two distinct binding sites on the thrombin molecule — the active catalytic site (via its N-terminal domain) and the fibrinogen-recognition exosite (via its acidic C-terminal domain, particularly the sulfotyrosine at position 63) — forming a tight, essentially irreversible, equimolar 1:1 noncovalent complex with thrombin. This dual-site binding confers exceptionally high affinity (Ki approximately 20 femtomolar for native hirudin) and specificity compared to univalent inhibitors. The critical mechanistic advantages over heparin are multiple: hirudin does not require antithrombin III as a cofactor (heparin does); it is not neutralized by platelet factor 4 or other circulating heparin-neutralizing proteins released from activated platelets; it directly inhibits both free thrombin in solution and thrombin bound to fibrin clots or the subendothelium — a population that heparin cannot adequately suppress; and it has no direct platelet-activating effects, avoiding heparin-induced thrombocytopenia (HIT). Because thrombin is the convergence point of the coagulation cascade — converting fibrinogen to fibrin, activating platelets, amplifying coagulation via factors V, VIII, and XIII, and stimulating endothelium — direct thrombin inhibition at these two sites simultaneously suppresses multiple pro-thrombotic pathways. Pharmacokinetically, recombinant hirudin (r-hirudin) is distributed in the extracellular space following intravenous injection, with a half-life of 1–2 hours under normal renal function; it is eliminated almost entirely by renal glomerular filtration in biologically active form, making dose adjustment mandatory in renal impairment. PEGylation of hirudin increases molecular weight, reduces renal clearance, lowers immunogenicity, and extends the circulating half-life. Recombinant forms (lepirudin, desirudin) preserve the core pharmacodynamic and pharmacokinetic properties of native hirudin with minor structural differences at the N-terminus.
Class: Direct thrombin inhibitor — naturally occurring 65-amino-acid peptide (and recombinant derivatives); anticoagulant agent
Administration & storage
- Administration
- Desirudin: subcutaneous injection into the abdominal wall or anterolateral thigh; alternate injection sites at each doseLepirudin (historical): initial IV bolus followed by continuous IV infusion via pump; not for subcutaneous use at therapeutic doses for HITDose adjustments are critical in renal impairment; renal function must be assessed before initiation and monitored during therapyNo antidote is available for hirudin overdose — hemofiltration or hemodialysis with high-flux membranes can partially remove hirudin in emergency overdose situations
- Storage
- Desirudin lyophilized powder: store at controlled room temperature 25°C (77°F). Reconstituted solution: use immediately; do not store. Protect from light. Do not freeze.
- Cautions
- Renal impairment is a critical safety concern: hirudin and its recombinant forms are eliminated almost exclusively by renal glomerular filtration. Accumulation in renal impairment leads to supratherapeutic anticoagulation and major bleeding risk. Dose adjustment is mandatory for CrCl <60 mL/min; lepirudin is contraindicated in severe renal failure without strict monitoring.,No specific antidote exists: unlike heparin (reversed by protamine) or warfarin (reversed by vitamin K or prothrombin complex concentrates), hirudin has no approved pharmacological antidote. In overdose, supportive care and high-flux hemodialysis for partial removal are the only options.,Bleeding risk: major bleeding is the primary adverse effect across all therapeutic applications. Intracerebral hemorrhage was observed at high doses in acute MI trials, leading to their termination. Concurrent use with thrombolytics, antiplatelet agents, or other anticoagulants substantially increases bleeding risk (PMIDs: 9469633, 8720743).,Antibody formation and anaphylaxis with lepirudin: lepirudin is immunogenic; anti-hirudin IgG and IgM antibodies develop in approximately 40–74% of patients treated with lepirudin for ≥5 days. Most antibodies do not neutralize anticoagulant activity; some paradoxically enhance it by slowing renal clearance of the drug-antibody complex. Severe anaphylactic reactions upon re-exposure have been fatal.,Monitoring complexity: aPTT-based monitoring of hirudin is unreliable at higher concentrations due to non-linearity of the aPTT standard curve. ECT provides linear monitoring across the full therapeutic range. Chromogenic substrate assays are accurate but not bedside-compatible. Inadequate monitoring increases risk of both underdosing (therapeutic failure) and overdosing (major bleeding).
Legal & regulatory status
Desirudin (Iprivask) is FDA-approved for prophylaxis of deep vein thrombosis (DVT) in patients undergoing elective hip replacement surgery, administered as 15 mg subcutaneous injection twice daily. Lepirudin (Refludan)…
Hirudin and its recombinant derivatives (lepirudin, desirudin) are not specifically listed on the WADA Prohibited List as of the current WADA 2024 Prohibited List. Anticoagulants do not fall under prohibited classes…
Desirudin (Revasc) was approved in Canada and several European countries for DVT prophylaxis after hip replacement surgery prior to the widespread availability of the Iprivask brand in North America. Lepirudin…
What it's studied for
- Prevention of deep vein thrombosis (DVT) after elective hip replacement surgery — desirudin (Iprivask/Revasc) Phase III RCT / FDA-approved indication
- Anticoagulation in heparin-induced thrombocytopenia (HIT) — lepirudin (Refludan) Regulatory approval / ACCP guideline-recommended
- Adjunctive anticoagulation in acute coronary syndromes (unstable angina and acute MI) — investigational / large RCT evidence Phase III RCT (non-approved; excess bleeding precluded approval for ACS)
- Clinical monitoring and dose-guided anticoagulation using ecarin clotting time (ECT) Clinical pharmacology / standard of practice
- Recombinant production for therapeutic and investigational use — biotechnology platform Translational / biotechnology validation
- Anti-inflammatory and renoprotective effects in hyperuricemia-associated kidney injury (preclinical/mechanistic) Preclinical / in vitro
Safety signals
- Renal impairment — critical accumulation and bleeding risk requiring mandatory dose adjustment
- Major bleeding, including intracranial hemorrhage
- Antibody formation and anaphylaxis with lepirudin (re-exposure risk)
- Absence of antidote — no specific reversal agent available
- Monitoring complexity — unreliable aPTT at supratherapeutic concentrations; ECT required for accurate high-range monitoring
- Lepirudin market withdrawal — drug no longer commercially available for HIT indication
Contraindications
About these dose ranges
Dose ranges below reflect commonly reported community protocols. Where published research cites a specific dose, the PMID is linked. Doses without citations are not clinical recommendations — they reflect what practitioners and researchers commonly report using.
Community-reported dosing
| Route | Dose | Frequency / Duration | Population / context | Source tier |
|---|---|---|---|---|
| Unspecified | 15 mg desirudin SC per injection | — | Adults undergoing elective hip replacement — DVT prophylaxis (desirudin, FDA-approved) | Research |
| Unspecified | Initial IV bolus 0.4 mg/kg (max 44 mg), followed by continuous IV infusion 0.15 mg/kg/hour (max 16.5 mg/hour); adjust to aPTT ratio 1.5–2.5 | — | Adults with HIT and associated thrombosis — anticoagulation (lepirudin, historical FDA-approved dosing) | Research |
| Unspecified | 0.1–0.5 mg/kg single and repeated doses IV or SC | — | Adults — pharmacokinetic studies of recombinant hirudin (r-hirudin) in healthy volunteers | Research |
| subcutaneous injection, abdominal wall or anterolateral thigh | 15 mg desirudin SC per injection | twice daily (every 12 hours), initiated before surgery | adults undergoing elective hip replacement surgery requiring DVT prophylaxis |