General Principles and Indications
Antifibrinolytic agents (or fibrinolysis inhibitors) are essential tools for managing bleeding. Their primary goal is to halt blood loss caused by pathological, excessive activation of the fibrinolytic system.
When the system responsible for clot breakdown becomes hyperactive, the patient is at risk of losing a critical volume of blood. In such cases, these agents are indicated.
Key clinical indications include:
- Surgery and Trauma: extensive trauma, major surgical procedures, and obstetrics.
- Liver Pathology: conditions disrupting the synthesis of natural coagulation factors or endogenous fibrinolysis inhibitors.
- Local Bleeding: menorrhagia (heavy menstrual bleeding) and prostatitis.
- Iatrogenic States: overdose of thrombolytic (fibrinolytic) drugs, where artificially induced fibrinolysis must be rapidly halted.
Mechanisms of Action
Broadly, drugs in this group are divided into two categories based on their basic mechanism of action:
- Agents that inhibit plasminogen activation (preventing the precursor from becoming an active enzyme).
- Agents that directly inhibit plasmin (blocking the already formed enzyme).
Aminocaproic and Tranexamic Acids
These are synthetic analogs widely used in clinical practice. They can be administered both orally (per os) and intravenously.
Aminocaproic acid (Aminocaproic acid) features an interesting dual mechanism of action:
- First, it binds to plasminogen, reliably blocking its conversion into active plasmin.
- Second, if plasmin has already formed, the drug prevents its destructive action on fibrin strands.
However, the drug has several side effects. Cardiovascular effects may include hypotension, bradycardia, and arrhythmias. Patients may also complain of dizziness and dyspepsia (nausea, diarrhea).
Its structural analog—aminomethylbenzoic acid—has a virtually identical mechanism of action.
Tranexamic acid (Tranexamic acid) works by inhibiting plasminogen activation. Compared to aminocaproic acid, tranexamic acid has significantly higher clinical efficacy and a longer duration of action.
Side effects of tranexamic acid include:
- Dyspeptic symptoms: anorexia, nausea, vomiting, and diarrhea.
- Neurological disturbances: dizziness and marked drowsiness.
- Allergic reactions: predominantly cutaneous manifestations.
Aprotinin: A Protease Inhibitor
Aprotinin is a potent inhibitor of proteolytic enzymes.
Its key mechanism of action is the direct inhibition of plasmin, the primary enzyme of fibrinolysis. In addition, aprotinin can suppress the activity of other proteolytic enzymes in the body.
Unlike synthetic acids, aprotinin is administered exclusively via the intravenous route.
Potential adverse effects include:
- Cardiovascular system: tachycardia and hypotension.
- Gastrointestinal tract: nausea and vomiting.
- Immune system: high risk of allergic reactions.