Thrombolytics are used in emergency treatment to unclog blood vessels. In what directions? What are these drugs? What are the risks and contraindications?
Definition: what is a thrombolytic?
Also called fibrinolytic, a thrombolytic allows to induce thrombolysis (or fibrinolysis). It is an emergency medical technique that consists of destroy a blood clot blocking a vein or artery. A thrombolytic is a drug reserved for hospital use, belonging to the family of antithrombotics. Administration is by injection into a vein or artery by a doctor.
It is a molecule which acts at the level of the blood clot by transforming plasminogen into plasmin. Plasmin is an enzyme capable of degrading fibrin, which is the protein involved in clot formation. So the blood vessel is unblocked, allowing restore blood circulation necessary for the delivery of oxygen and nutrients to the organs.
What are the indications for a thrombolytic?
A thrombolytic is used to destroy a blood clot in the following life-threatening situations:
- a pulmonary embolism with the pulmonary artery mostly blocked
- myocardial infarction
- extensive deep vein thrombosis (risk of becoming a pulmonary embolism)
- an obstruction of a venous catheter (medical device in the form of a tube)
- obliterating arteriopathy (narrowed or clogged artery) of the legs or arms associated with a risk of ischemia (decreased or stopped blood circulation in the affected area which may lead to necrosis).
- a stroke caused by a blocked blood vessel
Depending on the indication, the molecule used will not be the same. Use is possible in adults and children (regardless of age for urokinase, from 16 years for alteplase). Administration should be carried out as soon as possible after the onset of the first symptoms, this delay determines the effectiveness of the drug.
What are the best known thrombolytics in France?
In France, thrombolytics are reserved for hospital use. Some specialties have been withdrawn from the market. The drugs currently available are:
- Actilyse® (alteplase)
- Metalyse® (tenecteplase)
- Therasolv® and Actosolv® (urokinase)
What are the side effects of thrombolytics?
Before administering the treatment, the risk-benefit balance is assessed by a doctor. Thrombolytics frequently cause bleeding which can be cerebral, gastrointestinal, urogenital (lead to the presence of blood in the urine), pulmonary but also bleeding nose and gums. Cerebral hemorrhage can in some cases lead to death, especially in a patient with hemostasis disorders. The haemorrhagic risk may even be responsible for the occurrence of a embolism or stroke (very common with urokinase). Likewise, bruises and hematomas are common side effects. Also, mild allergies may occur (especially with urokinase) such as a hives, a rash or very rarely an allergic reaction serious causing death. Other side effects likehas fever, chills, nausea, and vomiting have been reported.
What are the contraindications of thrombolytics?
The main contraindications of thrombolytics are:
- a allergy to one of the components of the drug
- a recent severe bleeding or stroke recent (less than 6 months)
- a suspicion or history ofintracranial hemorrhage
- a surgery recent major (less than 2 months)
- A recent head trauma associated with cardiopulmonary resuscitation (less than 2 months)
- a severe unbalanced arterial hypertension
- a severe liver disease
- A peptic ulcer unhealed, esophageal varices
- a pancreatic diseaseinflammation of heart tissue
Thrombolytics are not contraindicated in pregnant or breastfeeding women. Before administering the drug, the benefits will be weighed against the risks involved.
What are the drug interactions of thrombolytics?
Due to the increased risk of bleeding, a thrombolytic should not be administered concomitantly with:
- an oral anticoagulant (fluindione, warfarin) or injectable (heparins, fondaparinux)
- an antiplatelet agent (acetylsalicylic acid, clopidogrel)
- a nonsteroidal anti-inflammatory drug (ibuprofen)
In addition, thrombolytics should not be combined with iodinated contrast agents (products used for carrying out diagnostic examinations such as an MRI). Indeed, their administration delays the destruction of the blood clot. The combination of a thrombolytic based on alteplase or urokinase and an inhibitor of the converting enzyme (antihypertensive) is contraindicated because it promotes theappearance of angioedema (subcutaneous swelling).
Sources:
– Public drug database
-ANSM
– Academy of Medicine
– pharmacomedical.org