Alteplase differs from streptokinase as it
**Core Concept**
Alteplase and streptokinase are both fibrinolytic agents used to treat acute ischemic stroke and myocardial infarction. They differ in their mechanism of action, pharmacokinetics, and clinical applications.
**Why the Correct Answer is Right**
Alteplase is a recombinant tissue plasminogen activator (tPA) that specifically activates plasminogen to plasmin, which then breaks down fibrin clots. This targeted action allows for more effective and safer thrombolysis, especially in the cerebral vasculature. In contrast, streptokinase is a non-specific activator of plasminogen that can also activate other proteases, increasing the risk of bleeding and allergic reactions.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because alteplase does not require concurrent administration of heparin, unlike streptokinase, which often requires heparin co-administration to prevent re-occlusion.
**Option B:** This option is incorrect because alteplase has a more favorable safety profile, with a lower risk of allergic reactions and bleeding complications, compared to streptokinase.
**Option C:** This option is incorrect because alteplase has a shorter half-life and more rapid onset of action compared to streptokinase, making it more suitable for acute ischemic stroke treatment.
**Option D:** This option is incorrect because alteplase is not more expensive than streptokinase, although its higher cost-effectiveness is due to its targeted mechanism and improved clinical outcomes.
**Clinical Pearl / High-Yield Fact**
When choosing between alteplase and streptokinase for thrombolysis, consider the patient's age, comorbidities, and the time elapsed since symptom onset. Alteplase is generally preferred for acute ischemic stroke within 3-4.5 hours, while streptokinase may be used in certain cases of myocardial infarction.
**Correct Answer: C. Alteplase has a more favorable safety profile and a shorter half-life compared to streptokinase.**