Thrombin, also known as activated coagulation factor II, is a powerful serine protease that plays a central role in the blood clotting cascade. In a medical context, it is used to control minor bleeding and oozing from capillaries and small vessels during surgery when standard techniques are ineffective. For researchers, it is a vital reagent for studying coagulation and other biological processes. However, it is a highly regulated substance and is not available for purchase by the general public or for home use.
Medical Sources: Hospitals and Surgical Centers
For patient treatment, thrombin is exclusively administered in a clinical setting by or under the supervision of a healthcare professional. It is not available for purchase at retail pharmacies. There are several types of topical thrombin approved by the FDA, differing primarily in their origin and manufacturing process.
Topical Thrombin Products
Medical-grade thrombin is typically sold as a sterile lyophilized powder that is reconstituted into a solution or as a pre-mixed liquid. It is then applied to the bleeding site, often with a carrier like an absorbable gelatin sponge or as part of a fibrin sealant. The main types available for clinical use include:
- Recombinant Human Thrombin (e.g., Recothrom®): This is a manufactured product created using recombinant DNA technology. It has the same amino acid sequence as human thrombin but is produced in a controlled environment, such as a Chinese hamster ovary (CHO) cell line, and is free from the risks of blood-borne pathogens or immunogenic reactions associated with animal-derived products.
- Human Plasma-Derived Thrombin (e.g., Evithrom®): This is extracted and purified from pooled human plasma. While it undergoes extensive viral inactivation and filtration to ensure safety, there is still a theoretical risk, albeit very low, of viral transmission.
- Bovine Thrombin (e.g., Thrombin-JMI®): This was historically the most common type and is derived from bovine (cow) sources. Its use has been associated with significant immunogenicity issues, leading to the development of antibodies that can cross-react with human clotting factors, potentially causing severe bleeding complications. Its use is less common today due to these risks, but it is still available.
Fibrin Sealants and Topical Hemostatic Kits
Thrombin is also a key component in fibrin sealants, which combine thrombin with fibrinogen to rapidly form a clot. These are often used for larger, more diffuse bleeding areas. Kits like Thrombin-JMI® with a syringe spray or epistaxis kit are designed for specific applications, such as controlling nosebleeds in a clinical setting.
Research and Laboratory Sources: Chemical Suppliers
For research and diagnostic applications, pure thrombin is available for purchase from specialized chemical supply companies. Researchers use this high-purity product to study the coagulation cascade, cleave fusion proteins, or use it as a component in cell culture.
Reputable Laboratory Suppliers
- Sigma-Aldrich: Offers high-purity thrombin from various sources, including human plasma and bovine plasma, for laboratory use. They also provide specifications for cell culture applications.
- Cayman Chemical: Stocks human plasma-derived thrombin (activated factor II) for research purposes. Their website provides detailed technical information for scientists.
- BioPharm Laboratories: Sells high-purity liquid bovine thrombin for research and manufacturing diagnostic kits.
- Block Scientific: Offers pre-packaged thrombin time reagents for laboratory coagulation testing.
When purchasing from these suppliers, customers must provide proof of their affiliation with a research or laboratory institution. The products are intended for in vitro (laboratory) use only and are not for human or animal injection.
Important Considerations for Thrombin Sourcing
- Prescription and Regulation: For medical use, thrombin is a prescription product. Its administration is restricted to trained healthcare professionals in controlled clinical environments. The U.S. FDA strictly regulates the use of these products.
- No Intravenous Injection: A critical safety warning associated with all thrombin products is that they must never be injected intravascularly. Intravenous injection can cause widespread, life-threatening clotting.
- Immunogenicity: The risk of immunogenic reactions, particularly with bovine thrombin, has led to a shift towards safer human plasma-derived and recombinant alternatives. Patients with prior exposure or known sensitivities should be monitored or use non-bovine options.
Comparison of Thrombin Types
| Feature | Bovine Thrombin (e.g., Thrombin-JMI®) | Human Plasma-Derived Thrombin (e.g., Evithrom®) | Recombinant Human Thrombin (e.g., Recothrom®) |
|---|---|---|---|
| Source | Purified from bovine plasma | Purified from pooled human plasma | Produced via genetically engineered cells (e.g., CHO) |
| Primary Risk | High potential for immunogenicity and severe bleeding due to anti-bovine antibodies | Theoretical risk of viral transmission, although manufacturing processes reduce risk | None of the above risks; low immunogenicity profile |
| Safety Profile | Black Box warning due to immunogenic reactions | Considered safer than bovine, with viral reduction steps | Safest option regarding antibody and viral risks |
| FDA Approval | Approved, but with significant warnings | Approved in 2007 | Approved in 2008 |
| Manufacturing | Standard purification from animal plasma | Extensive viral inactivation and filtration | Controlled recombinant DNA technology |
| Usage | Topical use only, typically with an absorbable sponge | Topical use only, can be liquid or part of a kit | Topical use only, often reconstituted from powder |
Conclusion
Thrombin is an indispensable medication and laboratory reagent, but its availability is highly controlled to ensure safety. For clinical application in controlling surgical bleeding, thrombin is a prescription-only product found in hospitals and surgical centers. Newer human plasma-derived and recombinant forms have largely supplanted the older, immunogenic bovine version for enhanced safety. Researchers seeking thrombin for laboratory studies must procure it from specialized chemical supply companies that cater to the scientific community. Regardless of the source, it is crucial to recognize that thrombin is for external, topical use only, and its intravascular injection is strictly forbidden due to life-threatening risks. Anyone interested in its medical use should consult a qualified healthcare provider within a professional clinical setting. For those in research, proper protocols and sourcing from a reputable lab supplier are paramount. For further reading, an authoritative source on the use of topical thrombin can be found in this evidence-based review.
