Immediate-release nifedipine is contraindicated for what reason in the treatment of acute MI?

Nifedipine, particularly in its immediate-release form, can lead to an increase in myocardial ischemia during an acute myocardial infarction (MI) due to its potent vasodilatory effects. These effects can result in significant hypotension, which, while also a risk in the medication's use, primarily contributes to worsening ischemia because it decreases coronary perfusion. This reduction in perfusion is particularly critical in the setting of an acute MI where the heart muscle is already compromised and struggling for oxygen.

In addition to this, during an acute MI, the goal of treatment is often to improve blood flow to the heart muscle, and the use of immediate-release nifedipine can inadvertently lead to increased heart rate and reduced myocardial oxygen supply, compounding the injury to heart tissue. Therefore, the primary concern with using immediate-release nifedipine in this context is its potential to worsen ischemia, making it contraindicated in the treatment of acute MI.