Thrombin is a powerful enzyme that plays a crucial role in the body's natural coagulation cascade, converting fibrinogen into the insoluble fibrin mesh that forms a blood clot. In medical practice, exogenous thrombin is used to aid hemostasis—the process of stopping bleeding—during surgical procedures. While the term "thrombin injections" is often used, most FDA-approved preparations are strictly for topical application to control minor bleeding and oozing. Different products are derived from distinct sources, which affects their brand name, safety profile, and usage. Understanding these differences is key for medical professionals.
Bovine Thrombin: Thrombin-JMI
Historically, bovine-derived thrombin was the first formulation approved for use in surgery.
- Brand Name: The most well-known brand for bovine thrombin is Thrombin-JMI.
- Source: This product is derived from purified bovine (cow) plasma.
- Application: Thrombin-JMI is used topically, often soaked into an absorbable gelatin sponge or applied as a spray to surgical bleeding sites.
- Key Consideration: A significant concern with bovine thrombin is its potential to trigger an immune response in some patients. The body can develop antibodies against the bovine protein, which may sometimes cross-react with human clotting factors, potentially leading to adverse events like bleeding or clotting disorders. For this reason, repeat exposure to bovine thrombin is often avoided.
Recombinant Thrombin: Recothrom
To address the immunogenicity concerns associated with bovine products, recombinant human thrombin was developed.
- Brand Name: Recothrom is the brand name for recombinant thrombin.
- Source: Unlike bovine thrombin, Recothrom is not derived from animal or human plasma. Instead, it is produced in a lab using recombinant DNA technology in a Chinese hamster ovary (CHO) cell line.
- Advantages: This production method significantly reduces the risk of triggering an immune reaction and eliminates the theoretical risk of transmitting blood-borne diseases associated with plasma-derived products. It provides a safer alternative for patients, especially those with prior exposure to bovine thrombin.
- Application: Recothrom is also for topical use and can be combined with absorbable gelatin sponges or applied via a spray applicator.
Human Thrombin: Evithrom
Another option is thrombin derived from pooled human plasma, which also carries reduced immunogenicity compared to bovine products.
- Brand Name: Evithrom is a brand name for human-derived thrombin.
- Source: Evithrom is manufactured from carefully screened and tested human plasma donations.
- Safety Profile: While stringent testing minimizes risks, the theoretical risk of blood-borne disease transmission always exists with plasma-derived products, though no cases have been reported for Evithrom.
- Application: Evithrom is used topically to aid hemostasis and can be mixed with a carrier or applied directly.
A Comparison of Thrombin Products
| Feature | Thrombin-JMI | Recothrom | Evithrom |
|---|---|---|---|
| Source | Bovine plasma | Recombinant DNA (CHO cells) | Human plasma |
| Brand Name | Thrombin-JMI | Recothrom | Evithrom |
| Immunogenicity | Higher risk of antibody formation, potential cross-reactivity with human clotting factors | Low risk of immunogenicity | Low risk of immunogenicity, no reported issues with cross-reactivity |
| Transmission Risk | None | None | Theoretical risk of blood-borne diseases |
| Approval | Approved for topical hemostasis | Approved for topical hemostasis | Approved for topical hemostasis |
| Application | Topical application (powder for solution) | Topical application (powder for solution, spray kit) | Topical application (solution) |
Specialized Application: Ultrasound-Guided Thrombin Injection (UGTI)
It is critical to distinguish the FDA-approved topical use from a specialized, often off-label procedure called Ultrasound-Guided Thrombin Injection (UGTI). This technique is primarily used to treat pseudoaneurysms.
A pseudoaneurysm is a hematoma (a collection of blood) that forms outside a blood vessel, typically after a catheterization procedure. Under ultrasound guidance, a small, highly concentrated dose of thrombin is injected directly into the pseudoaneurysm sac to induce a clot. This is different from the topical application in surgery and is not performed in the general circulatory system.
- Mechanism: Injecting thrombin directly into the pseudoaneurysm causes an immediate and localized thrombosis, effectively sealing the leak in the vessel.
- Advantages: UGTI is generally less invasive and often more comfortable for patients than open surgery or prolonged compression. It boasts a high success rate, even in patients on anticoagulant therapy.
- Safety: The procedure must be performed by a skilled professional under continuous ultrasound guidance to prevent accidental injection into the artery, which could cause a dangerous blood clot.
Side Effects and Risks
As with any medication, thrombin preparations carry risks that medical professionals must consider.
- Topical Preparations: The most critical warning is against systemic absorption. If thrombin enters the bloodstream, it can cause widespread and potentially fatal intravascular clotting. This is why the packaging and professional guidelines emphasize "DO NOT INJECT INTRAVASCULARLY".
- Hypersensitivity: Allergic reactions, including potentially life-threatening anaphylaxis, can occur, especially with non-human proteins. Patients with a history of hypersensitivity to hamster proteins should avoid Recothrom.
- Immunogenicity: The risk of developing antibodies is highest with bovine-derived thrombin (Thrombin-JMI). These antibodies can lead to adverse coagulation issues.
- Pseudoaneurysm Injection: Risks include accidental arterial injection, distal embolism, and incomplete thrombosis. Careful technique minimizes these risks.
Conclusion
When discussing thrombin injections, it is important to clarify the context. The vast majority of thrombin products are for topical use in surgery, and their brand names depend on their source: Thrombin-JMI (bovine), Recothrom (recombinant), and Evithrom (human-derived). Each carries different safety profiles regarding immunogenicity. A separate, specialized procedure involves injecting thrombin under ultrasound guidance to treat pseudoaneurysms, a technique distinct from the more common topical application. Always follow professional medical guidance regarding the appropriate use and application of these potent hemostatic agents. For more detailed clinical information on these products, authoritative sources like the U.S. Pharmacist provide extensive reviews.
For more information on topical hemostats, consider reviewing resources from the U.S. Pharmacist: Topical Hemostats - U.S. Pharmacist.
