Final answer:
When rtPA is administered, aspirin should not be given for at least 24 hours to avoid interfering with platelet action and increasing the risk of bleeding.
Step-by-step explanation:
When rtPA, or recombinant tissue plasminogen activator, is administered, it is important not to give aspirin for at least 24 hours. This is because aspirin interferes with the action of platelets, which could increase the risk of bleeding. Aspirin is known to prevent the formation of thromboxane A2, a potent aggregating agent, by platelets. Therefore, if aspirin is given while rtPA is being used, it could disrupt platelet function and further impair the blood clotting process.