Thrombolytics
When a blood clot is mobilized, it is called a thrombus or embolus. It moves
through blood vessels eventually causing a blockage—called a thromboem-
bolism—resulting in decreased blood flow (ischemia) that causes death (necro-
sis) of tissues in the effected area. Thromboembolisms disintegrate naturally in
about two weeks through the fibrinolytic mechanism, which breaks down fibrin.
Thrombolytics are drugs that promote the fibronolytic mechanism if admin-
istered within 4 hours following an acute myocardial infarction (AMI). An acute
myocardial infarction (heart attack) can be caused by a thromboembolism block-
ing a coronary artery. This results in decreased circulation to that part of the
heart. The ischemic (without oxygen) tissue becomes necrotic (dies) if left with-
out an oxygen supply. Thrombolytics prevent or minimize necrosis that results
from the blocked artery and therefore decreases hospitalization time. After
thrombolytic treatment, the patient is evaluated for cardiac bypass or coronary
angioplasty procedures.
Thrombolytics are also used for pulmonary embolism, deep vein thrombosis,
and noncoronary arterial occlusion from an acute thromboembolism.
Commonly used thrombolytics are streptokinase, urokinase, tissue plasmino-
gen activator (t-PA, Alteplase), anisoylated plasminogen streptokinase activator
complex (APSAC, Anistreplase), and reteplase (Retavase).
All of these drugs induce fibrin breakdown (fibrinolysis).
Allergic reactions can complicate thrombolytic therapy. Anaphylaxis (vascu-
lar collapse) occurs more frequently with streptokinase than with the other
thrombolytics.
Reperfusion dysrhythmia or hemorrhagic infarction can result if thrombolyt-
ics break up the clot after an MI. The major complication using thrombolytics is
hemorrhage. The hemorrhage is stopped by using aminocaproic acid (Amicar)
to inhibit plasminogen activation. The use of heparin with thrombolytic medica-
tions is commonly done and can prevent formation of new clots but requires
intensive care and close monitoring of the patient.A list of thrombolytic drugs is provided in the Appendix. Detailed tables
show doses, recommendations, expectations, side effects, contraindications, and
more; available on the book’s Web site (see URL in Appendix).Antilipemics
Antilipemics are drugs that lower abnormal blood lipid levels (see Table 19-4).
Lipids, composed of cholesterol, triglycerides, and phospholipids, are bound to(^366) CHAPTER 19 Cardiac Circulatory Medications