Which of the following is considered a drug therapy for post-heart attack treatment?

Thrombolytics are a class of medications that are specifically used in the treatment of heart attacks, particularly to dissolve blood clots that obstruct blood flow to the heart muscle. They work by breaking down fibrin, a protein that helps form blood clots. By doing this, thrombolytics can reopen blocked arteries quickly and help restore blood flow, which is critical in minimizing heart damage during a heart attack. This rapid intervention can improve outcomes for patients significantly.

In contrast, the other options, though they have important roles in medical treatment, are not primarily intended for treating a heart attack. Diuretics are used to reduce fluid overload in conditions such as heart failure, antibiotics are aimed at treating infections, and insulin is essential for managing blood glucose levels in diabetes. None of these options directly address the acute complications of a heart attack in the way that thrombolytics do.